C HAM BE R S'S INFORMATION FOR THE PEOPLE. NEW AND IMPROVED EDITION. CHAMBERS'S )RMATt0'N FOR TH-E PEO1 WILLIAM AND ROBERT CHAMBERS. V7 0 L-4 -U 1V:0 3. PHILADELPHIA: J. B. LIPPINCOTT & CO. 1857. EDITED BY VO L U VE I' 11 _A- a TE R. S,:IJ M _ L O, AC NID E D I VBUS X T DO PRE F A C E. SIX years have now elapsed since the completion of' TIE INFORMATION FOR THE PEOPLE' in its second and improved form. Owing to the rapid advance of almost every branch of science and art, this is a long period in the history of a work of the nature of an encyclopsedia. It has therefore appeared proper that these volumes should be recast, so as to adapt them as nearly as possible to the present state of human knowledge. Designed in an especial manner for the People, though adapted for all classes, tile work will be found to comprise those subjects on which information is of the most importance; such as the more interesting branches of science-physical, mathematical, and moral; natural history, political history, geography, and literature; together with a few miscellaneous papers, which seemed to be called for by peculiar circumstances affecting the British people. Thus everything is given that is requisite for a generally weil-irrformed mare in the less highly-educated portions of society, and nothing omitted appertaining to intellectual cultivation, excepting subjects of professional or local interest. It will be understood, then, that the' INFORMATION FOPR THE PEOPLE' is not an encyclopedia in the comprehensive meaning of the word, but rather one embracing only the more important departments of general knowledge. The ruling object, indeed, has been to afford the means of seyf-education, and to introduce into the mind, thus liberated and expanded, a craving after still farther advancement. The improvements of the present edition will be found very considerable. All the scientific treatises have been carefully remodelled, with due attention to recent discoveries. Subjects, the interest of which is past, have been omitted or greatly condensed, and others of a more enduring and important nature have taken their place. So much new information has been introduced, that the work is more encyclopedic than it has hitherto been. In the Index to each ivoliume will be found an explanation of, or reference to, almost every subject necessary in ordinary circumstances to be known. It is proper to mention that, in the preparation of this edition, great assistance has been rendered throughout by Mr DAVID IAGE, to whose varied talents we have on other occasions been in no small degree indebted. W. AND Ri. C. EdinbSzrgyz ArovenLmber 1848. CONTENTS. No. PAGE ASTRONOMY,...... 1 GEOLOGY, -. 2... 17 METEOROLOGY, 3... 33 PHYSICAL GEOGRAPHY, 4.. 49 VEGETABLE PHYSIOLOGY,. 5... 65 SYSTEMATIC BOTANY, 6-7... 81 ANIMAL PHYSIOLOGY-THE HUMAN BODY,. 8... 113 ZOOLOGY,... 9-12... 129 NATURAL PHILOSOPHY, 13... 193 MECHANICS-MACIH INERY, 1.14... 209 HYDROSTATICS —H YDR ULICS-PNEUMATICS, 15... 225 OPTICS-ACOUSTICS,.. 16... 241 ELECTRICITY-~MAGNETISM-ELECTRO-I0AGNETISI, - 17... 257 CHIRONOLOGY —HOROLOGY, 18... 273 CHEMIVSTRY,. 19.. 289 CHEMISTRY APPLIED TO THE ARTS, 20... 305 FICTILE MiANUFACTURES,..- 21... 321 TEXTILE MANUFACTURES,. 22... 337 MINING —MIINERALS, - - - - - - 23... 353 MELETALS-METALLURGY,.. -. 24... 369 THE STEALI-ENGINE, -. 25.. 385 INLAND CONVEYANCE, -. - 26... 401 MARITIME CONVEYANCe -.... 27,. 417 ARCHITECTURE,.... 28... 433 HIEATINGC —LIGHITING —VENTILATION. 29... 449 SUPPLY OF WATER-BATHS-SEWERS, 30... 465 AGRICULTUtE,.. 31... 481 CULTURE OF WASTE LANDS-SPADE HUSBANDRY, - 32... 497 THE KITCHEN GARDEN,.... 33... 513 THE FLOWER GARDEN,.. 34... 529 TIIHE FRUIT GARDEN,.... 35... 545 AMBORICULTURE,.... 36... 561 TIIE HORSE. - - - 37... 577 CATTLE-DAIRY HUSBANDRY,. 38... 593 THE SHEEP-GOAT-ALPACA,.... 39... 609 PIGS-RABBITS-POULTRY-CAGE-BIRDS,.. 40... 625 THE HONEY-BEE, -... 41... 641 THE DOG-FIELD-SPORTS1... 42... 657 ANGLING,.. 43... 673 SEA-rISHERIES, 4 44... 689 PRESERVATION OF HEALTH, -.... 45.. 705 FOOD-BEVERAGES,.... 46... 721 PREPARATION OF FOOD —-COOKERItY,. 47... 737 MEDICINE-SURGERY,.. 48... 753 CLOTHING-COSTUMSE, - 49... 769 INDEX, AND GLOSSARY OF TE1MS, - -..0. 785 INFORMATION FOR THE PEOPLE. ASTR ON OM Y. ASTRONOM1Y (from the Greek, astron, a star, and nos20, remoter regions of it, and still there is no end. In a law) is, comprehensively, that science which explsains this space, systems, consisting of suns and revolvilng the nature and motions of the bodies filling infinite planets, and other systems again, consisting of a nullmspace, including our own globe in its character of a berless series of such lesser systems, are suspended by planet or member of the solar system. The science the influence of gravitation, operating from one to may be divided into two departments-1. Descriptive another, yet each body at such a distance from anAstrosnosy, or an account of the systems of bodies oc- other, as, though the mind of mall can in some incupying space; 2. Mechanical Astrononoy, or an expla- stances measure, it can in none conceive. We begin nation of the physical laws which seem to have pro- with what is usually called the Solar System —-that is, duced, and which sustain, the arrangements of the the particular solar system to which our earth belongs, heavenly bodies, and of all the various results of the and of which the Sun. is the centre. arrangement and relations of these bodies. Uranographly is a subordinate departnment of the science, THE SOlAR SYSTEI. presenting an account of the methods which have been The solar system, so named from sol (Latin), the aclopted by astronomers for delineating the starry hea- sun, consists of the sun in the centre, upwards of thirty veils, and working the many mathematical problems of ascertained planets, and an unknown number of bodies which they are the subject. named comets. W~e say ascertained planets, because, from the recent discoveries of Leverrier and others, there seems a likelihood that we shall yet discover D E S C:R I P T I V:E A S T R O N O M Y. amore bodies of this nature. The word planet is from the Greek, planao, I wander, because the few such The early ideas of manlkind respecting tlse objects bodies known to the ancients were chiefly remarkable described by astronomy, proceeded upon appearances in their eyes on account of their constantly shifting which the uninstructed eye placed before them, and their places with reference to the other luminaries of were far from being true. It was supposed that the the sky. Comets are so named fiom com2n (Latin), a earth was, as it seems, a fixed plain, or, at the most, a, head of hair, because they consist of a long brush of fixed sphere, with an outer sphere, forming the heavens, luminous matter streaming from a point. revolving around it once in the twenty - four hours. Planets.-Of the planets, there are eight which may Even philosophers deemed the earth the central alid be said to rank in the first class, in as far as they move most important object in the system, and regarded the in orbits considerably removed from each other, and heavenly bodies-the sun, moon, planets, and stars-as are in this respect comparatively independent; while a comparatively small objects, fixed in different crystal group of small bodies, at least five in numbler, may be spheres, each of which observed its own laws of revo- said to have but one orbitual part in the series, and lution, according to the apparent motions of the bodies thus to be only co-ordinate with one of the rest. These fixed in it. It was not till after much study and inYes- thirteen are called prinlary planets, to distinguish tigation tlat even the most enlightened minds arrived them from others which move round certain of the at a knowledge of the truth; nor was it for some time primaries, and which are called secondaries, or satellonger that the idea of the earth not being in the centre lites, from satelles (Latin), originally signifying a lifeof the system, or anything but.a small and subordinate guardsman, but, by a wider application, one who follows part of it, was generally admitted. There is no room and serves another. here to trace all the steps by which the truth was as- The primary planets are —Mercury, Venus, the Earth, certained, or to argue the uninstructed mind Out of all Mars, Vesta, Ceres, Pallas, Juno, Astrna, Jupiter, its first and erroneous impressions. But it may be Saturn, Uranus, and Neptune. MIlost of these names hoped that when the actual constitution of the heavens are derived from the fabulous divinities of ancient has been described, it will be possible to form some Greece. The Earth has one satellite, the Moon; notion how the celestial objects in their real character Jupiter has fofir; Saturn, seven; Uranus is supposed and real arrangements happen to appear as they do to to have six; and Neptune one. the unassisted eye. The planets move round the sun on nearly one level The field contemplated by the astronomer is no less or plane, corresponding with the centre of his body, than INFINITE SPACE. So, at least, he may well pre- and in one direction, from west to east. The secondary sume space to be, seeing that every fresh power which planets, in like manner, move in planes round the he adds to his telescope allows him to penetrate into centres of their primaries, and in the same direction, No.. 1 CHAM~B3ERS'S INIFOlRMATION~ FOR THE PEOPLE. from west to east. These are denominated sevolstion- bright and luminous, as if giving out both heat and cary motions; and it is to be observed that they are light to the surrounding planets. But on this surface double in the case of the satellites, which have at once there occasionally appear dark spots, generally sura revolution round the primary, and a revolution, in rounded with a border of less cldark appearance; some company with the primary, round the sun. The path of which spots have been calculated to be no less than described by a planet in its revolution is called its 45,000 miles in breadth, or nearly twice as much as the orbit. Besides this motion of revolution, each planet, circumference of the earth. The region of the sun's secondary as well as primary, and the sun also, has bodyon which the spots appear, is confined to a broad a motion in its own body, like that of a bobbin upon space engirdling his centre. They are sometimes oba spindle. An imaginary line, forming, as it were, the served to come into sight at his western limb, to pass spindle of the sun or planet, is denominated the axis; across his body in the course of twelve or thirteen days, and the two extremities of the axis are called the and then disappear. At other times they are observed poles. The axes of the. sun and planets are all nearly to contract with great rapidity, and disappear like somieat a right angle with the plane of the revolutionary thing melted and absorbed into a boiling fluid. Upon movements. The motion on the axis is called the the bright parts of the sun's body there are also somerotatory motion, from rota, the Latin for a wheel. times observed streaks of unusual brightness, as if The sun, the primary planets, asnd the satellites, with produced by the ridges of an agitated and luminous the doubtful exception of those attending on Uranus, fluid. It has been surmised that the sun is a dark and overlooking that of Neptune, as yet unascertained, body, enveloped in an atmosphere adapted for giving move on their axes in the same direction as the revo- out heat and light, and that the spots are produced by lutionary movements, from west to east. slight breaks or openings in that atmosphere, showing /ice Sun ((D) is a sphere or globe, of 882,000 miles the dark mass within. Though so much larger than in diameter, or 1,384,472 times the bulk of the earth, the earth, the matter of the sun is of only about a fourth moving round its axis in 25 days. When viewed of the density or compactness of that of our planet, or through a telescope, the surface appears intensely little more than the density of water. Diagnetcers of Planets in Distances efPlanetsfroca Enlglish M'iles..the Sun. The Sun, - 882,000 Mercury,- - 3,140 ioO Mercury, - 37,000,000 Venus, - 7,800 Earth, - 0,000,000 Elarth, 7,912 Mars, - 14 95,000,000 Mars, - - 4,189 The Asteroids * M~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ars, -,0 1~44,000,000 The Asteroids, - Juie,*49,0, Jupiter, - 19,170. ~SJupiter,. - 490,000,000 Saturn, - - 79,042 Sataurn, - 906,000,000 ~Llanus, - 35,112 aur-nu,. 7,1142,t Uranus, - 1,823,000,000 Neptune, - -50,000 I ) Densities ef Ptanets, that of 9 _NLe~ptune, 2,900,000,000 tihe Ec, rot/s being considered / / as i. \ "is,', ofRevolution Thme Sun, - - 0.26' n. Mercury, - 295 Mercury, - 88 days. Venus, - 0'99 Venus, - 225... Earth, - - 1 Earth, - - 35... Mars, - - 079 Mars, - 7... The Asteroids, * The Asteroids, *... Jupiter, - - 0'25 Jupiter, - 4,3304... Saturn, - 0'11 Saturn, - 10,746... Uranus, - - 0'26 Urzanus, - 30,681... Neptune, - - Neptune, - 60,9906 The Solar System, to the orbit of Uranus, The sun is surrounded to a great distance by a faint been observed on the surface of this planet, particularly light, or luminous matter of extreme thinness, shaped in its lower or southern hemisphere. One has been like a lens or magnifying-glass, the body of the sun calculated at 103 miles in height, being about eighft being in the centre, and the luminous matter extencding thimes higher, in proportion to the bulk of the planet, in the plane of the planetary revolutions, till it termi- than the loftiest mountains uponi the earth. The matnates in a point. At particular seasons, and in favour- ter of Mercury is of much greater density thatn that of able states of the atmosphere, it may be observed, before the earth, equalling lead in weight. sunrise or after sunset, in the form of a cone pointing Veuss (9) is a globe of about 7800 miles in diameter, obliquely above the place where the sun is either about or nearly the size of the earth, rotating on its axis inI to appear, or which he has just left. It is termed the 23 hours 21 minutes and 19 seconds, and revolving Zodiacal Light. round the sun, at the distance of 68,000,000 of miles, inre ~ercuiry (~), the nearest planet to the sun, is a globe 225 cldays. Like Mercury, it is visible to an observer on of about 3140 miles in diameter, rotating on its axis in the earth only in the morning and evening, but for a 24 hours and 5 minutes, and revolving round the central greater space of timne before sunrise and after sunset. lumninary, at a distance of nearly 37,000,000 of miles, It appears to us the most brilliant and beautiful of all in 88 days. From. the earth it can only be seen oc- the planetary and stellar bodies, occasionally giving so casionally in the morning or evening, as it never rises much light, as to produce a sensible shadowv. Observed before, or sets after the sun, at a greater distance of through a telescope, it appears horned, on account of time than 1 hour and 55 minutes. It appears to the our seeing only a part of its luminous surface. The eye as a susall and brilliant star, but when observed illuminated part of Venus occasionally presents slight through a telescope, is horned or gibbous like the moon, spots. It has been ascertained that its surface is very because we only see a part of the surface which the unequal, the greatest mountains being in the southern sun is illuminating. Miountains of great height have hemisphere, as in the case of MIercury. The higher 2 ASTRONOMY. mountains in Venus have been estimated by some to telescope, her surface appears of unequal brightness, range between 10 and 22 miles in altitude. The planet and extremely rugged. The dark parts, however, are is also enveloped in an atmosphere like that of the not seas, as has been supposed, but more like the beds earth; hence the probability that its surface supports a of seas, or great alluvial plains. No appearance of kindred vegetable and animal existence. Mercury and water, or of clouds, or of an atmosphere, has been deVenus have been termed the Inferior Planets, as being tected. The surface presents numerous mountains, placed within the orbit of the earth. some of them about a mile and three-quarters in height, The Ealrth (s), the third planet in order, and one of as has been ascertained by measurement of the shadows the smaller size, though not the smallest, is important which they cast on the neighbouring surface. The to us, as the theatre on which our race havre been placed tops of the mountains of the moon are generally shaped to' live, move, and havae their being.' It is 7912 miles like a cup or basin, wvith a small eminence rising fiolm the in mean diameter, rotating on its axis in 24 hours, at a centre, like many volcanic hills on the earth. It has mean distance of 95,000,000 of mliles from the sun, hence been surmised that the moon is in a volcanic state, round which it revolves in 365 days 5 hours 48 mli- as the earth appears to have been for nmany ages before nutes and 49 seconds. As viewed from another of the the creation of man, and that it is perhaps undergoing planets, suppose the moon,' the earth would pre- processes calculated to niake it a fit scene for animal sent a pretty, variegated, and sometimes a mottled and vegetable existence. appearance. The distinction between its seas, oceans, The moon, turning on its axis once in a little more continents, ancl islands would be clearly marked; they than 27 days, presents every part of its surface in sucwould appear like brighter and darker spots upon its cession to the sun in that time, as the earth does in 24 disk. The continents would appear bright, and the hours. The day of the moon is consequently nearly a ocean of a darker hue, because water absorbs the greater fortnight long, and its night of the same duration. The part of the solar light that falls upon it. The level light of the sun, falling upon the moon, is partly abplains (excepting, perlhaps, such regions as the Arabian sorbed into its body; but a small portion is reflected deserts of sand) would appear of a somewhat darker or thrown back, and becomes what we call inoonlight. colour than the more elevated and mountainous regions, The illuminated part, from which we derive moonlight, ias we find to be the case on the surface of the mloon. is at all times increasing or diminishing to our eyes, as The islands wrould appear like small bright specks on the moon proceeds in her revolution round cur globe. the darker surface of the ocean; and the lakes and When the satellite is at the greatest distance from the mlediterraneatn seas like darker spots or broad streaks intersecting the bright parts, or the land. By its revolution round its axis, successive portions of the surfaice would be brought into view, and present a different aspect from the parts which preceded.'-D)ich's C'elestial Scenery, p. 135. The form of the eartlh, and probably that of every other planet, is not strictly spherical, but oblately spheroidal; that is, flattened a little at the poles, or: iii'J extremities of the axis. The dialneter of the earth at the axis is 26 miles less than in the cross direction. This peculiarity of the form is a consequence of the rotatory motion, as will be afterwards explained. The earth is attended by one satellite, the MIooei ( O) ) (i), which is a globe of 2160 miles in diameter, and consequently about a 49th part of the bulk of the earth, revolving round its prilmary in 27 days 7 hours Phases of the Mloeon. 43 minutes and 11 seconds at the distance of 237,000 43 minutes T one 11 seconds, rt the distance eath than sun, we, being between the two, see the whole of the niles. The mnoon is 400 timies nearer the earth than illuminated surface, which we accordingly term full moon. As the mooni advances in her course, the lumiinous side is gradually averted from us, and the lmloon k..........._ —-_-_ _...... is said to watie. At length, when the satellite has got ______~==~-~-~T —~-~-~-~.-~ —— _ ___I*'between the earth anld the sun, the luminous side is =_....-=_=~-;-Z-=_~;~-~-~-~ —~-~ ______ entirely lost sight of. The mloon is then said to chanfge. Proceediig in her revolution, she soon turns a bright edge towards us, which wre call the zezw moon. This graclually increases in breadth, till a moiety of the circle is quite filled up; it is then said to be half moon. The luminary, wvhe on the increase from cnew to half, is termed a crescent, from cresceits, Latin for increasing; — i___ =E= -3Eig= and this word has been applied to otlher objects of the same shape —for instance, to a curved line of buildiings. In the early days of the new moon, we usually see the dark part of the body faintly illuminated, an appearnance termed the old rzoon ir the sezu moon's ai'mas. This faiint illumination is produced by the reflection of the sun's light from the earth, or what the inhabitants of the moon, if there were any, might be supposed to ____= __=-'= —-;~T~L~~ —-~ —~I_______ __ consider as iroonlight. The earth, which occupies one ___________, I~-~-i eins variable place in the sky of the moon, with a surface ______II —-— =-;-~=~_~'_;-~ — thirteen times larger than the apparent size of the moon in our eyes, is thein at the full, shining with great lustre Telescopic appearance of the Mioon. on the sunlless side of its satellite, ald receiving back the sun is; but its diameter being at the same time a small portion of its own reflected light. The light, 400 times less than that of the sun, it appears to us of then, which makes the dark part of the moom visible about the samue size. The moon rotates on her axis in to us, mnay be said to perform three journeys-first exactly the same time as she revolves round the earth. from the sun to the earth, then froim the earth to the She consequently presents at all times the same part of moon, and finally from the moon back to the earthher surface towards the earth. Inspected through a before our eyes are enabled to perceive this object. 3 CHAMBERS'S INFORMIATION FOR THE PEOPLE..Mars (s), the fourth of the primary planets, is a 1847), a sixth and seventh have been announced as adglobe of 4189 miles in diameter, or little more than a ditions to the group, under the names of Hebe and Iris. half of that of the earth; consequently the bulk of this Jujpiter (4) is the largest of all the planets. Its diaplanet is only about a fourth of that of our globe. It meter is nearly eleven times that of the earth, or 89,170 performs a rotation on its axis in 24 hours 39 minutes miles, and its volume is consequently 1281 times that and 21- seconds, and revolves round the sun, at a dis- of our globe. The density of Jupiter is only a fourth of taclle of 144,000,000 of miles, in 686 days 23 hours 30 that of the earth, or about the lightness of water. It minutes and 41 seconds. iMLars appears to the naked performs a rotation on its axis in 9 hours 55 minutes eye of a red colour; from which circumstance it was, and 33 seconds, or about two-fifths of our dlay. It reprobably, that the ancients bestowed upon it the name volves round the sun, at a distance of 494,000,000 of of the god of war. Inspected through a telescope, it miles, in 4332 days 14 hours and 39 minutes, or nearly is found to be occasionally marked by large spots twelve of our years. Viewed through a telescope, and dull streaks, of various forms, and by an unusual Jupiter appears traversed by dark lines, or belts, brightness at the poles. As the bright polar parts which occasionally shift, melt into each other, or sepasometimes project from the circular outline of the rate, but sometimes are observed with little variation planet, it has been conjectured that these are masses for several months. These belts are generally near the of snow, similar to those which surround the poles of equator of the planet, and of a broad and straight fornm; our own planet. but they have been observed over his whole surface, Vesta, Juno, Ceres, Pallas, and Astrce'c, are five small and of a lighter, narrower, and more streaky and waTvy globes, revolving between the orbitsof Mars and Jupiter, appearance. It is supposed that the dark parts are in paths near and crossing each other, and which are not lines of the body of the planet, seen through openings only much more elliptical than the paths of the other in a bright cloudy atmlosphere. planets, but also rise and sink much farther from the Jupiter is attended by four satellites, which revolve plane of the general planetary revolutions. Vesta (6) is round it, in the same manner as the moon round our of a bulk only 1-24,000th part of the bulk of the earth, globe, keeping, like it, one face invariably presented to with a surface not exceeding that of the kingdom of their primary. They are of about the same size, or a France. It revolves round the sun in 3 years 66 days little larger diameter than our moon; the first having and 4 hours, at a mean distance of 224,950,000 of miles. a diameter of 2508, the second of 2068, the thiird of Though the smallest of all the planets, it gives a very 3377, and the fourth of 2890 miles. The first revolves brilliant light, insomuch that it can be seen by the round the primary planet in 1 day 18 hours 28 minutes; naked eye. Juno (~) is 1425 miles in diameter, andl the second in 3 days 13 hours 14 minutes; the third presents, when inspected through the telescope, a white in 7 days 3 hours 43 minutes; and the fourth in 16 and well-defined appearance. Its orbit is the most ec- days 16 hours 32 minutes. These satellites frequently centric of all the planetary orbits, being 316,300,000 of eclipse the sun to Jupiter; they are also eclipsed by the miles from the sunl at the greatest, and only 180,000,000, primary planet, but never all at the same time, so that or about one-half, at the least distance. It revolves his dark side is never altogether without moonlight. round the sun in 4 years and 128 days. In the half of The satellites of Jupiter were discovered by Galileo, the course nearest to the sun, the motion of the planet being anlong the first results of the invention of the is, by virtue of a natural law afterwards to be ex- telescope. They have been of great use in several asplained, more than twice as rapid as in the other part. tronomical calculations of importance, particularly in Ceres (Q) has been variously represented as of 1624 suggesting the theory of the gradual propagation of and 160 miles in diameter. The astronomer who cal- light. It having been observed that their eclipses culated its diameter at 16'24 lmiles, at the same time always took place sooner than was to be expected when believed himself to have ascertained that it has a dense the earth was near Jupiter, and later when it was at atmosphere, extending 675 miles from its surface. It the greatest distance, an astronomer solved the diffiis of a reddish colour, and appears about the size of a culty by supposing that light required some tirle to star of the eighth magnitude. Ceres revolves round travel-a conjecture which was afterwards confirimed the sun, at a distance of 262,800,000 of miles, in 4 by other observations. years 7 months and 1 0 days. Pallas (,) has been repre- Seatuzs (f), seen through a telescope, is the most resented as of 2099 miles in diameter, with an atsmo- markable of all the planets, being surrounded clby a ring, sphere extending 468 miles above its surface. Anlother and attended by seven satellites. In bulk, this is the astronomer has alloweid it a diameter of only l 10 miles. second of the planets, being 79,042 miles in diameter, It revolves round the sun, at a mean distance of or about 995 times the volume of the earth. Its surface 263,400,000 of miles, in 4 years 7 months and 11 days. appears slightly marked by belts like those of Jupiter. However unimportant it may appear beside the larger It performs a rotation on its axis in 10 hours 29 planets, it has a peculiar interest in the eyes of astro- minutes, and revolves round the sunl, at a distance nomers, on account of its orbit having a greater incli- of 906,000,000 of miles, in 10,759 days 5 hours 16 lnation to the plane of the ecliptic than those of all the minutes, or about 29- of our years. At such a distance larger planets put together.'Astrcea revolves round the from the sun, that luminary must be diminishedl to sun at a mean distance of 244,000,000 of miles in 1521 one-ninetieth of the size he bears in our eyes, and the days. It is esrident that these small planets are not heat and light in the samne proportion. The matter of distinct and independent in the same degree with Mler- Saturn is one-ninth of the density of our earth. cury, Venus, and the other primaries. Cosmogonists The ring of Saturn surrounlds the body of the planlet presumte that the matter which in other cases has gone in the plane of its equator. It is thin, like the rim of to form one planlet of the first ranlk, has ini their case a spinning-wheel, andc is always seen iwith its edge prebeen separated into several parts, assuming various, but sented more or less directly towards us. It is luminous connected orbits. with the sun's light, and casts a shadow on the surface These five planets, which are sometimnes called aste- of the planet, the shadow of which is also sometimes roids, have only recently become known to mankind. seen falling on part of the ring. The distance of the Ceres was discovered at Palermo; in Sicily, on the 1st inner edge from the planet is calculated at about 19,000 of January 1801, by M. Piazzi, who gave it this naime miles; its entire breadth from the inner to the outer in honour of the tutelary goddess of his native country. edge is 29,533; the thickness is not more than 100. Pallas was discovered at Bremen, in Lower Saxony, In certain positions of the pianet, we can see its suron the 28th of March 1802, by Dr Olbers. Juno was face at a considerable angle, and the openings or loops discovered by Mr Harding, at the observatory of Lilien- which it forms at the sides of the planet. At other thal, near Bremen, on the 1st of September 1804. Vesta times we see its dark side, or only its edge. From was discovered on the 29th of March 1807, by the same observations made upon it in favourable circumstances, astronomer who had discovered Pallas. Astr ea was it is found to be apparently divided near the outer edge not discovered till 1845. Even while we write (August by a dark line of nearly 1800 miles in breadth, as if it 4 ASTRONOMY. were divided into two concentric rings. From other Comets usually h'ave two parts-a body or nucleus, and appearances, it has been surmised to have other divi- a tail; but some have no tail, while others hive no sions, or to be a collection of several concentric rings. apparent body. The nucleus appears a brilliant, opaque; It is also occasionally marked by small spots. The and solid body; or thin vapoury luminous mass, of globuring of Saturn rotates on its own plane in 10 hours 32 lar form-so thin in some cases that the stars have minutes 15 seconds and a part of a second, being about been seen through it. The tail is a still lighter lumithe same time with the rotation of the planet. The seven satellites of Saturn revolve around it, on _ the exterior of the ring, and almost all of them in nearly the same plane. They are so small as not to be visible without a powerful telescope. The two inner ones are very near to the outer edge of the ring, and can only be discerned when that object is presented so....... _____ exactly edgeways as to be almost invisible. They have then been seen passing, like two small bright beads, nous vapour, surrounding the body, aind streanmin far along the minute thread of light formed by the edge of out from it in the direction contrary to its forward mothe ring. The three next satellites are also very small; tion. A vacant space has been observed between the the sixth is larger, and placed at a great interval from body and the enveloping matter of the tail; and it is the rest. The seventh is the largest; it is about the equally remarkible that the tail has in some instances size of the planet Mars, and is situated at nearly appeared less bright along the middle, immediately thrice the distance of the sixth, or about 5,100,000)mIiles behind the nucleus, as if it were a stream which that from the body of Saturn. The revolutions of these nucleus had in some measure parted into two. satellites range from 1 to 79 days; and it has been In ignorann ages, the sudden appearance of a comet ascertained of some of them that, according to the in the sky never failed to occasion alarm, both on acusual law of secondary planets, their rotations on their count of its threatening appearance, and because it was axes and their revolutions round their primnary are considered as a sign that war, pestilence, or famine was performed in the same time, so that, like our moon, about to afflict mankind. Knonwledge has dispelled all they always present the same face to the centre of their such superstitious alarms; but yet we are not well acsystem. The orbit of the seventh satellite is much in- quainted with the nature of comets either as'regards dlined to the plane of Saturn's equator. their revolutions, or their physical constitutions. Ur/anus, or Herschel (I ), is a globe of 35,112 miles Out of the great multitude-certainly not less than in diameter, rotating on its axis in 7 hours, andi per- 1000-which are supposed to exist, about 150 have forming a revolution round the sun, at the distance of been made the subject of scientific observation. In1,823,000,000 of miles, in 84 of our years. It was dis- stead of revolving, like the planets, nearly on the plane covered, on the 13th of March 1781, by Sir William Her- of the sun's equator, it is fbound that they approach his schel, at Bath. The sun to this remote planet must ap- body from all parts of surrounding space.' At first, pear only a 400th part of the size which he bears in our they are seen slowly advancing, with a comparatively eyes. Two satellites are known, and other four are sus- faint appearance. As they approach the sun, the mnotion pected, to attend upon Uranus. The two which have becomes quicker, and at length they pass round hinm been observed circulate round their prinmary in orbits with very great rapidity, and at a comparatively small almost perpendicular to the ecliptic, and are furthersup- distance from his body. The comet of 1680 approached posed to move in a direction contrary to that of all the within one-sixth of his diameter. After passing, they other planetary motions-namely, from east to west. are seen to emergoe from. his rays, with anl' imense The existence of Ieptene was ascertained by caleu- increase to their former brilliancy, and to the length of lation by M. Leverrier of Paris, in September 1846, their tails. Their emeotion then becomes gradiually slower, and the planet wvas consequently detected at the first and their biiltian cy diminishes, aeld at length they nre search for it by MI. Galle of Berlin. -Having a diameter lost in distance; It has been ascertained that their of 50,000 miles,' it ranks as the third planet of our movement round the sun is in accordance with the system in point of magnitudle; it is nearly 2,900,000,000 same law whlich regulates the planetary movemnents: of miles distant from the sun, from which it receives being always the ttuiicker the nearer to his body, and only a nine-hundredth part of the light which falls on the slower the more distant. In the remoqte parts of our sphere. Its years is 167 of ours, or 60,996 days, space their motions nmust be extremely slow. ancd it has already been ascertained to be attended by Three comets have been observed to return, and their at least one satellite, and to be surrounded by a ring periods of revolution heave been calculated. The most lilke that of Saturn. remarkable of these is one usually'denominated Hal: Some idea may be obtained of the comnparative size ley's Comet frnom the astronomer who' first calculated of the principal objects of the solar system, by suppos- its period. It revolves round the sun in about seventying a globe of two feet diamneter, placed in the centre of five years, its last appearance being at the close of 1834: a level plain, to represent the sun; a grain of mustard- Another, called Encke's Comet, firom Professor Encke seed, placed on the circumference of a circle 164 feet of Berhie, has been found to revolve once in 120'7 days, or 3' years; -but in t Ihis case the revolving body isi~VI thZYS in diameter, for Mercury; a pea, on acircle of 284 feet, or 3 yeas; but in this case the revolving body is for Venus; another pea, on a'circle of 430 feet, for the found, at each successive approach to the sun, to be a Earth; a large pin's head, on a circle of 654 feet, for little earlier than on the'previous occasion, as if, from Mars; five minute grains of esand, in circles of from some retardting cause, its orbit were graidually lessening, 1000 to 1200 feet, for Vesta, Ceres, Pallas, Juno, ancd and as if the comet might consequently in time fall Astrna; a moderate-sized orange, on a circle of nearly intothe sun. The third, named Beila's Comet, from iM. half a mile in diameter, for Jupiter; a small orange, Beila of Josephstadt, revolves round the sun in 63 years. on a circle four-fifths of a mile in diameter for Saturn; It is very snmall, and has no tail. In 1832, this comet a small plum, on a circle of a mile and a half in dia- passed through the earth's path about a month before meter, for Uranus; arid an ordinary plum, on a circle the arrival of our planet at the same point. -If the of two miles and a half, for Neptune. It is calculated earth had been a month earlier at that point, or the that the united mnass of the whole of the planets is not comet a month later in crossing it, the two bodies would above a 600th part of the mass of the sun, have been brought together, and the earth, in all probability, would have instantly become unfit for the exCOMIETS. istence of the human family. Comnets are often affected Comets are light vapoury bodies, which move round in their motions by the attraction of the planets.' Jupithe sun in orbits much less circular than those of the ter, in particular, has been described by an astronomer planets. Their orbits, in other words, are very long as a perpetual stumblingblock in their way. In 1770, ellipses or ovals, having the sun near one of the ends. a comet got entangled amidst the satellites of that 5 CHAMBERS'S INFORMATION FOR THE PEOPLE. planet, and was thereby thrown out of its usual course, It is ascertained, beyond doubt, that some stars, at while the motions of the satellites were not in the least one time visible, and registered by ancient astronomers, affected by its proximity. are not now to be seen; while many instances are on Comets often pass unobserved, in consequence of the record of stars which have come into sight for a time, part of the heavens in which they move being then and then gradually vanished. A large star suddenly under daylight. During a total eclipse of the sun, which became visible 125 years before Christ, and attracted happened sixty years before Christ, a large comet, not the attention of Hipparchus, who was thereby induced formerly seen, became visible, near the body of the ob- to draw up a catalogue of stars, the first ever made. scured luminary. On many occasions their smallness In the year 389, a star blazed forth in the constellation and distance render them visible only by the aid of the Aquila,% and after remaining for three weeks as bright telescope; on other occasions they are of vast size. as the planet Venus, disappeared. A star appeared in The comet now called Halley's, at its appearance in the region of the heavens between Cepheus and Cassi1456, covered a sixth part of the visible extent of the opeia in the years 945, 1264, and 1572, and is supposed heavens, and was likened to a Turkish scimitar. That to be one which comes within our sight once every of 1680, which was observed by Sir Isaac Newton, had three hundred and nineteen years, or thereby. At its a tail calculated to be 60,000,000 of miles in length, a last appearance, it was very attentively observed by the space two-thirds of the distance of the earth front the celebrated Danish astronolmer Tycho B3rahh, who pubsun. There was a comet in 1744, which had six tails, lished a volume respecting it. Its appearance was so spread out like a fan across a large space in the hea- sudden, that, in returning from his laboratory to his vens. The tails of comets usually stretch in the direc- dwelling-house, he found a group of country people tion opposite to the sun, both in advancing and retiring. gazing at it, and was satisfied it had not been in that quarter of the sky half an hour before. It was then THE STARS. as bright as Sirius, and continued till it surpassed The idea at which astronomers have arrived respect- Jupiter when brightest,c and was visible at mid-day. ing the stars, is, that they are all of them suns, resema- It disappeared entirely about eighteen months after bling our own, but diminished to the appearance of being first observed. Another bright star appeared, in mere specks of light by the great distance at which they the constellation Serpentarius, in October 1604, and reare placed. As a necessary consequence to this sup- mained for a year. It is mentioned by contemporary position, it may be presumed that they are centres of writers, that at the birth of Charles II., in 1630, a large light and heat to systems of revolving planets, each of star, never before observed, appeared in the daytime, which may be further presumed to be the theatre of as if to mark something extraordinary in the fortunes a vital existence. of the child that day ushered into existence. Other The stars seen by the naked eye on a clear night are instances have been noticed in still more recent times; not above a thousand in number. This, allowing a like but, upon the whole, this is a point in which astrononumber for the half of the sky not seen, gives about mical observation is defective. It seems, however, to two thousand in all of visible stars. These are of dire- be clearly ascertained that some, if not all of the stars, rent degrees of brilliancy, probably in the main in pro- have periodical motions throughout space, some more portion to their respective distances from our system, rapid than others. In several of the instances where but also perhaps in some measure in proportion to their the period is short, there is no want of positive knowrespective actual sizes. Astronomers class the stars ledge. It has been ascertained, for instance, that the under different snagnitudes, not with regard to apparent star Omicron, in Cetus, has a periodical movement ocsize, for none of them present a measurable disk, but cupying 334 days. It is seen as bright as a star of the with a regard to the various quantities of light flowing second magnitude for about a fortnight; then gradually from them: thus there are stars of the first magnitude, diminishes for three months, till it becomes invisible, the second magnitude, and so on. Only six or seven in which state it remains for five months, when it again varieties of magnitude are within our natural vision; becomes visible, and gradually increases till it regains but with the telescope, vast numbers of more distant its former brightness, more or less-for it does not stars are brought into view; and the magnitudes are always reach the same degree of lustre. The star now extended by astronomers to at least sixteen. Algol, in the constellation Perseus, continues visible The stars are at a distance from our system so very during a period of sixty-two hours, when it suddenly great, that the mind can form no idea of it. The loses its splendour, and from a star of the second magbrilliant one called Sirius, or the Dog-star, sup- nitude, is reduced, in three hours and a-half, to the posed to be the nearest, merely because it is the most fourth; after which it begins to increase, and in three luminous, has been reckoned by tolerably clear cal- hours and a-half resumes its former size. There are culation to give only 1-20,000,000th part of the light eleven other stars which exhibit analogous phenomena, of the sun: hence, supposing it to be of the same size, some of them at intervals of five hundred years, to and every other way alike, it should be distant from our which eve may look forward without any danger of misearth not less than 1,960,000,000,000,000,000 miles. An takle. Astronomers have long been of opinion that our attempt has been muade to calculate the distance of solar system might have a motion through ipace. From Sirius by a trigonometrical problem. It may be readily recent observations, it is now believed to have such a supposed that the position of a spectator upon the earth motion; nay, the whole of the stars of our cluster apwith respect to celestial olbjects must vary considerably pear as moving round a fixed point. The situation of at different parts of the year: for instance, on the 21st this point has been determined by Dr Miidler of Dorpat of June, he must be in exactly the opposite part of the as in the small group of stars called the Pleiades. The orbit from what he was on the 21st of December-in- distance of our sun from that point is calculated at deed no less than 190,000,000 miles from it. This 34,000,000 of times that of the earth from the sun. Dr apparent change of position of celestial objects, in con- Midler considers that the stars are crowded immedisequence of this movement, is called paraellax. Now, ately round the centre; then a belt of comparatively it has been found that Sirius is so distant, that an vacant space; then again a crowded belt; and so on angle formed between it and the two extremities of alternately to the extremity. Our sun is supposed to the earth's orbit is too smazll to be appreciated. WVere it so much as one second, or tohe 3600th part of a de- r It may be stated here, in anticipation of more particular exgiee, it could be appreciated by the nice instruments f we pZlanations to be given afterwards, that the starry heavens are by gow re sse, s- t tisnte h.Iise o-astronomers mapped out into a series of constellations, or ascluenow pos; but S it is lnot beven this. It is hence con- semblages of stars, each of which bears the name of some figure eluded that Sirius must be at least 19,200,000,000,000 or other object-as Aquila the Eagle, cetus the Whale, Castor and miles distant, however much more! Supposing this to Polux, twin demigods of the Greek mythology, &c. Each parbe its distance, its light would take several years to ticular star in a constellation, in the order of its magnitude, is reach us, though travelling, as it does, at the rate of distinguished by a letter of the Greek alphabet, and when these 192,000 miles in a second of time! are exhausted, with a numbern 6 ASTRO NOMY. revolve round a central sun, at the rate of 2,200 the entire extent of this star-system, composed as it is miles a minute; yet the whole revolution requires of millions of millions of distinct bodies i 18,200,000 of our years! Another variety in the nature of these luminaries isEMOTE SR-SYSTEMSNEBUL their being in some instances not single stars, as they Our own star-system, inconceivably vast as it is, is appear to the naked eye, but a group of two or more, but an item of the heavenly inventory. Far beyond its evidently, from their motions, forming one system. The bounds, the telescope of HI-erschel has descried similar star Castor, in one of the Twins, is found, when much systems in great numbers, each hanging in some tolermagnified, to consist of two stars, of between the third ably defined shape in the vast empyrean, and each and fourth magnitude, within five seconds (a very small capable of being resolved, not exactly into stars, though space) of each other. Sir William Herschel made these are in some instances visible, but into what has observations upon more than 500 stars of,this kind, been expressively called star-dust, a collection of small where the distance is not more than half a minute (also brilliant particles, each of which would probably apa very small space); and to this list a foreign astro- pear a distinct sun under a stronger power of artificial nomer has added five times that number. Nor is there vision. Observations have been made upon these starreason to suppose that, in all these instances, one of the systems chiefly in the direction of the thinner parts of our stars is at a great distance behind the other, and that own system, where the sky is clearest of our own stars, they are only brought together by the accident of our and where of course they are most distinct from other position. Many of the double stars, no doubt, are thus and nearer objects. But even in these limited fields of accidentally brought together; but of a great number, the sky, very great numbers have been seen-between it has been fully ascertained that they are each a sys- 1000 and 2000 in the northern hemisphere alone-a tem, with a reciprocal relation to each other. They number, we must recollect, exceeding that of all the orare therefore called Binary Stars, It is generally dinarily visible stars in the same section of the heavens. observed that they move round each other within a certain time, and in elliptical orbits; the revolution X of Castor, for instance, is supposed to be accomplished - aI in 252 years; of g in Ursa Major, in 584 years; of 70 I 4 Ophiuchi, in 80~ years. In fact there is the same +' variety in this branch of the starry system as in its'. ~ ~ j-. + other depart ments, a1nd the revolutions of the few bi- ~. ~.~ i +::. nary stars that have been accurately surveyed range ~,k. from 43 to 1200 years. Several of these duplicate l V s 4 stars have made a revolution since they were first ob- A W a + < served, and are now advancing in their second period. _ a x~tZf - " One, g Hercules, was seen double, in 1782, by Sir - r t(Y 8 William Herschel; in 1795, it was hardly distinguish- +,_ able to be double; in 1802, it was double no longer, -. v t the one being eclipsed by the other, though a small'2 part of one was still jutting out at the side of the other: astronomers are now watching to observe them once RemoteStar-System. more become separate. Whether one of these stars They are of various forms, but in general, as has been serves to the other as a sun, or whether both are suns, said, tolerably well-defined. Many appear as spherical or whether the organised life with which they are pro- clusters, with a crowding of the star-dust towards the bably stored be of a kind.which can endure a perpetual centre: of this kind there is a brilliant example in the light and heat thrown froml the one to the other-or in constellation Hercules. It has been remarked, that in what other manner these immense worlds are put to the worlds about the centre of such clusters, the visible use-it would be vain to inquire. One remarkable heavens must be inconceivably brilliant, though they peculiarity in, them is, the variety of tints apparent in will have no appearances resembling our Milky Way. the light emitted by a considerable number of them; There is another spherical class, in which the external but no accurate account has yet been given of the rea- parts are the most brilliant: in these cases, the visible son of this wonderful difference of colour in the stars. heavens of a world near the centre will probably be Perhaps the most magnificent of all the starry phe- almost entirely composed of milky way. From our nomena is the.lJilky Way. This, as is generally known, earth these annular clusters are presented in various is a broad belt, of whitish lustre, which stretches round points of view, some so nearly edgewise, that we can the whole sky, being parted into two streaks for a large barely see the long line of thin matter in the centre. part of the circuit. The ancients formed the mean Several exhibit to Lord Posse's telescope most remrmarkidea of this light, that it was the milk spilt by the able and even startling forms; one being somewhat nurse of Mercury, one of the deities; hence its name. like an anchor, another like a crab, and so forth. When examined by a telescope, it is found to consist Surprising to relate, there are mlore than one bearing entirely of stars,' scattered by millions,' as Sir John a strong resemblance to the form which has been preHerschel beautifully describes them,' like glittering sumed as that of our own star-system-nalmely, a flatdust on the black ground of the general heavens.' tened mass, with a brilliant annmular exterior, partilg The average magnitude of these stars is about the tenth flatwise into two at one part! In the agellanic clouds, or the eleventh, and hence their invisibility to the naked a nebulous object inll the southern hemisphere, there is eye. It is a very remariable circumstance, that though one remote star-system (30 Dorad'ls), describedi by Sir the stars of the larger magnitudes are scattered with John Ierschel as c consisting of a number of loops considerable equality over the whole heavens, there is united in a kind of unclear centre or knot, like a buntzc/ a notable clustering of the smaller ones towards the of riibbonzs disposed iss what is called a trce-lover's.. body of this ring. Sir William Herschel, by gauging, konot!'' We are,' says an astronomer who possesses as it were,. the depth of our starry system in this and eloquence worthy of his noble science,'lost in mute other parts, arrived at what hlie believed to be an ap- astonishment at these endless diversities of character proximation to the figure of the system itself-namlely, and form. But in the apparent aim of things near and an elongated cake-shaped mass, parting flatwise into around us, we may perhaps discern some purpose two at one particular part of the exterior (where the which such variety will also serve. It seems the object Milky Way is double), and in which our solar system or result of known nmaterial arrangements, to evolke was placed somewhat nearer the one extremity than every variety of creature, the condition of whose being the other. Where the distance between two stars is so can be made productive of a degree of durability; and great as we have seen-and we can suppose the dis- perhaps it is one end of this wonderful evolution of tance between all the rest to be no less-what must be firmanlents of all orders, that there, too, the law of 7 CHAMBERS'S INFORMATION FOR THE PEOPLE. vrariety may prevail, andl room be found for unfolding velling through the intervening abysses during centhe whole riches of the Almighty.' The vast general turies whose number stuns the imagination. There distance of these clusters, their distinctness from our must be some regarding which that faint illumination own system; and their relative distances, have been informs us, not of their present existence, but only that determined bythe comparative powers of the telescopes assuredly they were, and sent forth into the In-finite employed in observing them. Some of them are dis- the rays at present reaching us, at anll epoch farther tant from us many thousands of times the distance of back into the past than this momentary lifetime of Sirius, the nearest of our own stars. man, by at least thirty millionls of years!' Astronomers have long had under their observation a set of peculiar objects, apparently within the limits URANOGRAPHY. of our star-system, andc callecld Nebuce, from their filmy Under this term (delineation of the heavens) may be cloud-like appearance. There is one of magnificent comprehended all those arrancgements which have been appearance in the girdle of the constellation Andro- madle by astronomers for artificial representation of the meda, and another still~ more splendid in the sword- heavens, and for the working of the many mathematical hilt of Orion, both visible to the naked eye. Some problems of which the heavenly bodies are the subject. of these objects are of irregular form, stretching like The stars, as they appear in their places on the apa fratgnlent of semi-pelluccld nmembrane over the sky, parent concave sphere of the heavens, are represented with patches of briglhter matter scattered irregularly in proper arrangement oni the celestial globe, which is throughout their extent. In others, the bright patches expressly designed as a miniature of that sphere, but are of greater intensity, so as to have the decided bearing also the fanciful figures assigned to the constelappearance of gatherinsgs of the matter towards a par- lations, and the lines necessary for the working of vaticular point. Others there are in which these bright rious problems. It is required that, in the first place, parts seem nearly disengaged from the surrounding we give a brief description of the terrestrial globe, or thin matter or only bedded on a slight background similar miniature representation of the earth. composed of it. In a fourth class, we see detached Astronomers, for the convenience of their science, masses, approaching more or less to a spherical form, have supposed certain lines to pass through and around and with various ineasures of comparative brightness the globe. One, passing through the centre, between towards the centre, until they resemble a star with only north and south, is called the axis of the globe, from a a slight bus around it. WVhen telescopes of high powers G-reek word signifying a-le. The two extreimities are were applied to these bodies, many of them were re- called the poles, from the Greek word polos, signifying solved into dense clusters of stars; but others could a pivot. A line girding the globe in the middle, or cutnot thus be resolved, and had such a peculiar appear- ting it into two equal portions, is styled the equator; all ance, that it was surmised that they were not starry to the north land south of which are respectively called masses, but patches of diffused matter in the course of the northerni and southern hemispheres. The circuit of being condensed to stars and systems-belated portions, tihe earth, both in its girth between east and west, and so to speak, of the same soft and diff:used material, between north and south, is divided into 360 parts, which, countless ages ago, was condensed into the de- called degrees. At the distance of twenty-three and fined bodies foruing the remainder of our star-system! This surmise was readily supported by many, on the NOTH POLE belief that such ullcondensed suns were likely to exist, and that the hypothesis furnished a ready basis whereon to found the history and conlnection of the solar sys- / tem. -But- in 1846, the powerful telescope of Lord Rosse showed that one of the most lmarked of these Topo C.... \ nebulme (that in Orion) did really consist of an im- i mense irreguilar lass of: stars,. undiscernible before, E from its being situated so remotely in-the depth of the Wr'T EAST starry spaces. It has consequently been pronounced as extremely doubtful if there are any masses of diffused, & 0o or, properly speaking, nebulous matter in the regions \ of space. (See OPTICS, p. 253.) The discovery, however it may affect theories, infinitely exalts our conceptions of the magnitude and extent of the inaterial universe. It teaches us to regard the farthest and filmiest speck which the most sour: POLE powerfal telescope can descry, as a:mass of worlds melted, by- distance,- into a dim light, but comprising a-half nearly of these degrees from the equator, in both individclualities as perfect, and at the same time as pro- directions, are two parallel lilies called the tropics, and gressive ina their: natures, as our own.' 5What mean, at the same distance from each pole is a parallel circle, for instalnce,'I says Professor Nichol in a recent work, styled in the one case the arctic, and in the other the those dim spots, which, unknown before, loom in anztarctic ciircle.. The space between the tropics is called greater and greater numbers on the horizon of every the torrid zone, because the sun, being always vertical new instrument, unless they are gleams it is obtaining, in some part of that space, produces a greater degree on its own frontier, of a mighty infinitude beyond, also of heat than what is felt elsewhere., The spaces bestuddedrith glories, and infolding what is seen as a tween the tropics and the arctic and antarctic circles are minute and'subservient part? Yes; even the six-feet called the tennperate, and' the spaces within these latter mirror, after its powers of dclistinct vision are exhausted, circles the frigid nones. Lastly, a line which cuts the becomes in its turn simply as the child gazing on these equator obliquely, touching upon opposite points of the mysterious lights with awful and hopeless wonder. I tropics, is called the ecliptic. The ecliptic and equator shrink below' the conception that. here-even at this are called greater circles, because they cut the earth at threshold of the attailable-bursts forth on my mind! the thickest parts;' the others are called lesser circles. Look at a cloudy speck in Orion, visible, without aid, A series of lines drawn froni pole-to pole over the to the well-trained eye; that is a stellar universe of earth's surface (like the division lines of a peeled majesty altogether transcendent, lying at the verge of orange), and cutting the equator at right angles, are what is knlown. Well, if any of these lights from afar, calledl neeridians (from the Latin word nieridies, midonl which the. six-feet mirror is now casting its longing day), or lines of longitude. Every place upon the earth eye, resemble in character that spot, the systems fronm is supposed to have one of these passing through it, whicli they come are situated so deep in space, that no although only 24 are described upon the terrestrial ray from them could' reach our earth until after tra- globe. When any one of these is opposite the suin, it 8 ASTRONOMY. is then mid-day or twelve o'clock with all the places The declination of the -sun, or other heavenly body, is situated on that meridian, and consequently midnight therefore called north or south declination, according with those on the opposite meridian on the other side to its proximity to the north or south pole of the of the earth. The exact situation of a place upon the heavens; hence it follows, that when the sun's decliearth's surface, or its latitude and longitude, is deter- nation is 10 degrees north, he is vertical at a place mined by means of these circles. They are all divided, whose latitude is 10 degrees north. But the right as already stated, into 360 parts, which parts are called ascensions do not so correspond with the longitudes, dearces; these. degrees again into 60 equal parts, called simply because the first point of the constellation Aries mi'zutes; the minute into 60 others, called seconds; does not correspond to the first meridian (Greenwich); andcl so on. They ale all indicated by certain signs iand because the longitudes are not measured quite placed behind the figure, and near the top of it-thus round, as the right ascensions are. 8~ 5' 7" is 8 degrees 5 minutes 7 seconds. A degree is The sun, which is always in the ecliptic, has of course 60 geographical miles, or about 69 English statute miles; no latitude, but he passes through all the degrees of a minute is the 60th part of that; and so on. The lati- longitude in a year. When any other celestial object rtde of a place is its distance measured north or south has the same longitude as the sun, it is said to be in fiom the equator. If it lies north of that line, it is said cojllnctiosa with him; and when the difference of to be in north latitude; if south of it, in south latitude. longitude amounts to 180 degrees, half the circle of the There being only 360 degrees in the circumference of heavens, it is said to be in opposition to him. Both the earth, and the distance from the equator to either these terms are comprehended in that of syzygy, which, of the poles being only a fourth part of it, a place can when applied to any celestial object, mleans that it is never have more than 90 degrees of north or south either in conjunction or opposition to him. What is latitude. Tlie loigtgitde of a place is the distance of called an equinoctial colure, is a great circle supposed its meridian from another, which is called the first to be drawn through the pole of the ecliptic and the mleridian. The first meridian is quite arbitrary, and it points where it intersects the equator. The solstitial is a matter of indifference through what point we draw colues is a similar circle, which passes through the solit, provided it be settled and well known hich one stitial points at right angles to it. The former colure is we adopt, so as to prevent mistakes. Foreigners fixed a secondary to the ecliptic, and the latter a secondary upon the principal observatories of their respective to both it and the equator. The equinoctial points countries. In Germany, the island of Ferro is gene- are Aries and Libra, where the ecliptic cuts the equator. rally adopted; in France, the observatory of Paris; The solstitial points are Cancer and Capricorn; and and in Englland, that of Greenwich. Longitude is when the sun is in either of them, he is at his farthest reckoneid either east or west of the first meridian; and distance above or below the equator. 180 is therefore the utmost degree of longitude. Some Allusion has already been made to the constellations geographers, however, reckon longitude all the way or fanciful figures marked on celestial globes, to aid in round the globe. From the shape of the earthl, which distinguishing the position of the stars. The earliest is flat at the poles, the degrees of longitude decrease astronomers seem to have adopted the idea of thus as we approach these in either direction. In order to mappig out the starry heavens, being no doubt at measure latitude, artificial globes are furnished with a first led to do so by the slight resemblances borne by brass meridian circle, on which the degrees are marked. various groups of stars to familiar terrestrial objects. Longitude is measured by a similarly graduated circle, Thus a group in the northern part of the slky bears terlled the artificial 70orizo01, in which the golobes are some resemblance to an ancient wain, or to a plough suspended. as also to the hinder part of an animlal, with its The other great circle, called the Ecliptic, is dividecl tail extended; hence it has been evariously called the into twelve parts, called signs, which bear the nanmee Plozgh, Ursa Major, or the Greater Bear, and Charles's of the constellations throughi which this circle passes in the heavens, as shall be afterwards explained. -- There are other smaller circles which run round the earth parallel to the equator; these are called'paas o of latitdude, because, being everywlhere at the saene distance from the equator, the latitude of every point..= contained in any one of them is the same. - _'._ The celestial globe, representing that apparent outer sphere, the sky, in the centre of which the earth seems suspenlded, is marked by lines similar to those upomn --— _ — the terrestrial globe, each line upon the latter beims supposecl to hlave at correspondiing line opposite to it ______ in the heavens. Thus the celestial sphere is divided into the samle number, of degrees as the terrestrial. The celestial poles correspond to those parts of the... __ = heavens to which the terrestrial poles always point. The point of the heavens directly over our heads, or the Constellation Urs Biajor. very summit of our sky, is called the zenith, and is a T/Vaiz-the last term being in honour of the illustrious sort of pole or middle, point of the visible half of the French kihng Charlemagne. (In ordinary globes, Ursa heavens; the poinht which we would see directly beneath Major is alone marked.) Another group, in the our feet, if the earth could be seen through, is called southern heavens, conveys the idea of a mnan's figure, the eadir, and forms a pole to the nether half of the and has been called Orion, frome ase early Greek senmiheavens. The celestial equator corresponds also to the divine hero of that name. Sonme of the nazmes of the terrestrial, and is, like it, everywhere 90 degrees distant constellations were conferred by Chaldean observers from the poles.- The equator of the earth thus lies several hundred years before our era: others have been directly unsder that of the heaavens: the ecliptic does given within the last few ages. Particular stars of exactly the same, and cuts the former also at an angle large magnitude also bear particular names, generally of 23 degrees 28 minutes. Arabic, having been affixed by Arabian astronomersThe place where the ecliptic cuts the equator at the as Aldebaran, Dubbe, Alioth, &c. Arcturus and the vernal equinox is called the first point of Aries;'and group of small stars called the Pleiades, are alluded froml this point the distamnce of all celestial bodies east- to in the book of Job, which is well knowin to be one ward and e;estward of it is measured. This is called of the earliest of the Scriptural compositions, and protheir right ascension, and corresponds to terrestrial longi- bably not less than 3000 years old. tude. Their latitude and decliznation are reckoned, respec- Twelve of the constellations are placed in thlat part tively, north and south of the ecliptic and the equator. of the heavens which is opposite to the ecliptic in the 9 CHAMBERS'S INFORMATION FOR THE PEOPLE. terrestrial globe; that is to say, the plane of the contact. We may see this law operating if we take two planetary motions, if extended to the stars, would fragments of cork, no matter how small, and set them strike the part occupied by these constellations. This afloat on the surface of a cup of water. If kept a conpart of the celestial globe is called the Zodiac, and siderable way apart, the impediments to their mutual these are named the Zodiacal Constellations, or more attraction are too strong, and they therefore do not commonly, the kSigns of the Zodiac. The zodiac is a meet. But if brought within a short distance of each zone or belt, extending eight or ten degrees on each other, we shall observe them begin mutually to exercise side of the ecliptic. It is divided into twelve parts, an influence over each other, and immediately they each of thirty degrees, called the signs of the zodiac. will rush together, and so remain. The names of the signs, and the days in which the sun Material laws are equally ready to act on a large as enters them, are as follow:-Sp ring signs-Aries, the on a small scale, and on a small as upon a large one. Ram, 21st of March; Taurus, the Bull, 19th of April; The same attraction of cohesion which causes the tear Gemini, the Twins, 20th of May. Scmrmer signs- drawn from our eye by sympathetic feeling to be round, Cancer, the Crab, 21st of June; Leo, the Lion, 22d of produced the spherical form of the vast orbs which July; Virgo, the Virgin, 22d of August. These' are people space. These, being originally fluid masses, called Northern Signs, being north of the equator. gathered themselves round a centre, by the irresistible Auttumnal signs-Libra, the Balance, 23d of September; force of the law of the attraction of cohesion. So also Scorpio, the Scorpion, 23d of October; Sagittarius, the are the planets restrained in their position regarding Archer, 22d of November. TWinter signs-Capricornus, the central luminary, by the force of the sanme law. the Goat, 21st of December; Aquarius, the Water- We have next to consider the laws which regulate bearer, 20th of January; Pisces, the Fishes, 19th of the motion of masses of matter:February. These are called Southern Signs. Within A mass of matter set in motion upon the surface of the zodiac. are performed the revolutions of all the the earth, or within the compass of the atmosphere, principal planets. The twelve signs of the zodiac are invariably comes sooner or later to a stop. If we roll represented by astronomers thus; — a ball along the surface, it goes briskly for a while, cy3 Aries A, Leo *I Sagittarius then slowly, and finally it stops, and remains at rest. 8 Taurus Virgfo A Capricorn What causes it to stop is the resistance it meets with II Gemini I Libra Aquarius from the roughness of the ground, and the opposing Z Cancer ll% Scorpio X Pisces fluid (atmosphere) in which it moves. It is precisely when as much force has acted in opposition to its motion, as was exerted in setting it agoing, that it comes to a pause. Were it not, however, for this XMECHANICAL A STRONOMY. opposing force, the ball, once set in motion, would travel on and on for ever. It is the province of Mechanical Astronomy to ex- Just so the orbs of space, once set in motion, go on plain the physical laws which seem to have produced, and on perpetually, there being nothing whatever to and which sustain, the arrangements of the bodies oppose their progress. This applies as well to their occupying space, as well as all the various results of spinning or rotatory motion on their axes, as to their the arrangement and relations of those bodies. progress along their orbits. If a top were set a-spinIt may, in the first place, be proper to explain what ning on a smooth marble tablet, underneath the exis meant by a physical law. In the operations of hausted receiver of an air-pump, it would be found to nature, certain results are invariably observed to take keep in motion for a far longer space of time than in place as a consequence of certain circumstances. This any ordinary circumstances, for then there would be has suggested to the mind of man that there is an comparatively little air to give resistance to its rotaorder in all things, by virtue of which they are regu- tion, and the chief opposition would lie in its friction lated to the best general purposes, the authorship of against the tablet. Could the air be entirely drawn the order being no doubt the same as the authorship away, and the top be made to spin in a state of suspenof matter itself-that is to say, referable to the Divine sion, it would be in precisely the same circumstances as Being. Any such regulation, therefore, we term a law an orb revolving on its axis in space, and in that case of matter, or a phlysic.l law. it would never stop as long as all the circumstances remained unaltered. LAWS OF ATTRACTION AND MlOTION. But the orbitual revolutions of planets are circular. We have first to consider the laws by virtue of which Why should they be so 1 Because these orbs are particles andcl masses of mzatter attract each other, as far under the influence of both the law of attraction and as these are concerned in the province of Mechanical the laws of motion. Assuming the nebular hypothesis Astronomy:- to be true, the impulse which they originally obtained Particles of matter, when brought close together, or tended to throw them off in a direct line into space, in within insensible distances, have a tendency to cohere, the plane of the ecliptic. But the law of attraction or stick together; and this operates in all cases, unless prevented this result, and caused them to assume a there be opposing influences of superior force. It is circular course round the parent orb. They were protermed the attraction, qf cohesion. pelled by the one-cause (the centrifugal or centre-quitParticles of matter have also a tendency to move or tingp force), but restrained by another (the centripetal be drawn towards each other. This is called the at- or centre-seeking force-that is to say, attraction), and traction of gravitation, because it is what the weight they therefore settled into paths where the two forces or gravity of an object depends upon. balanced each other. Under the influence of the attraction of cohesion, To explain. If we take any circular body, say a particles of fluid matter, when suspended at a proper common grinding-stone, and, having first put a few distance from other objects, arrange themselves round pieces of clay upon its rim, cause it to revolve quickly a centre, and tiake a globular form. The dew-drop, in a horizontal manner, it will be found that the pieces suspended from the point of a thorn or blade of grass, of clay, one after another, fly off in straight lines from is a familiar example of matter thus acting. If two the rim. The cause of this is, that each particular such drops are brought close together, they will unite; part of the rim of the grinding-stone, at every instant a new and common centre will be instantly established of its revolution, is describing a straightforward movefor both, and they will resolve themselves into a new ment, and has itself, from the revolutionary motion, a mass equally globular as before. tendency to go straight on, and is only kept in its place Under the influence of the law of gravitation, when by being fixed to the rest of the stone. Every bit of any two masses of matter are brought within a certain clay that flies off, receives, at the instant of its parting, distance from each other, they will, if there be no the force of the straightforward impulse which at that sufficient obstacle, rush together, and then remain in moment affected the part of the rim where it rested; 10 ASTRONOMY. and hence its going off in a straight line. It is to be the slower movements of pendulums at the equator, observed, however, that the earth immediately begins that Sir Isaac Newton first conceived the idea of the to act upon the flying piece of clay, and draws it down- spheroidal foerm of the earth, which he ascertained to wards to itself in a bending line, its last movements be of less diameter at the poles than at the equator, as being, in fact, a part of a circle. This is the power of 298 is to 299, or by twenty-six miles. attraction, which in this case is exercised in much The orbits of the planets, it has been already seen, greater force by the earth than by the grinding-stone; are not strictly circles, but rather ellipses,- the sun were the grinding-stone the sole mass of matter near being in each case placed in one of the foci-that is, by, and the opposing force of the atmosphere with- the centre of one end of the ellipse. I-How should this drawn, we should see the clay begin to fly round the circumstance affect the revolutionary motion. It might stone in a circular course. be Supposed that, when the planet came to the part of And this naturally brings us to consider the corn- its course where it is nearest to the sun, the attractive parative powers of attraction exercised by different force would be greater, and that some derangemnent objects. A large mass has a much greater power of might take place. But this is not the case. At that attraction than a small one. When two of unequal part of the course the planet moves faster than elsebulk are brought near each other, we shall only be sen- where, and thus baffles the greater attractive force. sible perhaps of the large one drawing the small one This phenomenon is particularly apparent in comets, to it, and see no attractive power in the small one which have so eccentric an orbit. whatever. In reality, each mass, however small in The determination of the elliptical paths of the comparison, exercises a certain degree of attractive planets is due to the German astronomer Kepler, to power; and this power will depend expressly upon its whom we are also indebted for the discovery,'that the relative bulk and density, according to fixed regula- velocity of a planet's movement in its orbit is inversely tions of the nicest kind. as the square of the distance from the sun.' Thus One great and important law presides over the at- when the distance increases from 9 to 10, the velocity traction which one mass exercises over another. This diminishes at the rate of 100 to 81; so that at the relates to the distance between the two masses. ~We least distance we have the greatest speed, and vice verstl. shall suppose two globes of unequal size. When the This law is also known to astronomers as the law of small one is removed to as great a distance from the esual areas, because the areas swept over by the line large one as there is space between'-the surface of the joining the sun and planet-technically the radius large one and its centre (that is to say, the distance of vector-are equal in equal times. a semi-diameter of the large one), the attractive force Another discovery of Kepler established that there is diminished one-half. When it is removed to twice is a relation between the times respectively required that distance, or two semi-diameters, the attraction is by the planets for their revolutions, and their various diminished to a fourth. When it is removed to the distances from the sun. At a first glance, we are distance of three semi-diameters, the force is lessened struck by the fact, that the periods of revolution into a ninth; to four semni-diameters, a sixteenth; to five, crease more than in proportion to the distances. For a twenty-fifth; and so on; the diminution being always example, the period of Mercury is about 88 dclays, and as the squares of the amount of semi-diameters of dis- that of the Earth 365, being in proportion as 1 to 4.15 tance, or these sums nultiplied by themselves. The (or about 4 1-7th), while their distances, respectively moon is distant from the earth sixty of the earth's semi- 37,000,000 and 95,000,000 of miles, are in the less prodiameters; consequently the attractive power exercised portion of I to 2.56 (or a little more than 2~); and a by the earth over the moon is only a 3600th part of similar remark holds good in every instance. If we what it would exercise at its surface. take the squares of the distances, we arrive at nothing In the revolution, then, of a planet round the sun, satisfactory, for it considerably exceeds the proportion and of a satellite round a planet, there are various forces of the periods. If, however, we take the squares of the at work, all of them in the nicest proportion to each periods of two planets, we find they are in exactly the other, and to the mass of each body. There is first soame proportion to each other as the cubes of the mean the amount of motion resulting from the original ins- distances. Some may find a difficulty in understanding pulse; then the amount of attraction exercised by the the nature of this calculation; but its ingenuity and its central and larger over the smaller orb-the one pull- results form one of the highest boasts of astronomical ing outwards, and the other pulling inwards, but both science.' When we contemplate,' says Sir John Herin union attended writ the result of a circular or revo- schel,' the constituents of the planetary systeme from lutionary motion. the point of view which this relation affords us, it is no Gravity has not the same force at all parts of the longer mere analogy which strikes us-no longer a earth's surface. At the equator, the centrifugal force general resemblance among themi, as individuals indeproduced Iy the rotating motion is greatest; it declines pendent of each other, and circulating about the sun, in both directions towards the poles. In proportion as each according to its own peculiar nature, ared connected the centrifugal force is greater, the attractive power with it by its own peculiar tie. The resemblance is now of the mass of the earth is less, for the first of these perceived to be a true fas/ily likeness; they aie bound forces is directly counteractive of the other. There is up in one chain-interwoven in one web of mutual of course least attractive power at the equator; and relation and harmonious agreement-subjected to one bodies are there drawn with less force towards the pervading influence, which extendsfrom the centre to centre of the earth than would be found to be the the farthest limits of that great system, of which all of case elsewhere. Yet this difference is not great, for them, the earth included, must henceforth be regarded even at the equator the attractive force is 288 times as members.' that of the centrifugal. Neither does the difference The solar system, though composed of many different tell in the weighing of objects, for in that case two masses distant from each other, is to be considered equcivalents are used, and if a certain object is lighter, with respect to other masses as oze mnass, having a so also is the weight put into the opposite scale. The centre of gravity, by which its position with respect to difference was first detected, in consequence of pen- other nasses is regulated. The nearest stars no doubt dulum clocks being found to go slower as they were exercise the force of gravitation upon it, so as to keep brought towards tropical latitudes. It was ascertained it in its position; and it also acts in the same way upon that the pendulum of a clock which went right at them. It is therefore not strictly correct to speak of London, required to be one-eighth of an inch shorter the solar systemn, or any part of it, as ssspescged in space, (by which means its motion was accelerated) when it for that term implies a hanging from a fixed point. It was placed upon the equator. This effect, however, is is, in reality, kept at its place by attractive influences not altogether owing to the increase of centrifugal force, exerted all round it by other mnasses. In like mianner but partly also to the greater distance of the equator we are to suppose our star-cluster as poised by the sauce from the centre. And it was from a speculation as to forces in the midst of other clusters; and these, again, 11 CHAMBERS'S INFORMATION FOR THE PEOPLE. poised by others-an idea which leads us on -and on being situated in one of the foci-that is, not in the through the fields of infinity, till the mind loses itself centre, but near one of the ends of the oval-shaped in an effort beyond its finite powers, and pauses con- figure. Neither does the earth go round the sun in an tented to wonder and adore upright or perpendicular position; its axis is slanting or oblique. This obliquity amiounts to 23 degrees 28 DIURNAL AND ANNUAL MtOTION OF THE EARtTH. DIURNAL AND ANNAL MOTION T ET. minutes nearly. The points at which the ecliptic cuts The earth is to be considered as a globe of nearly the equator are called nodes: the period of time at 8000 miles in diameter, performing a rotatory motion which it does this, the eqsisoxes (a term signifying on its axis once every twenty-four hours. This motion equal nights, for the days and nights are then of equal is at the rate of 1036 miles an hour to places at the length all over the world). In consequence of this obequator, but only 560 miles at London, and a gradually liquity, during one part of the earth's course the north diminishing amount ill places nearer to the poles. pole is turned towards-the sun, and the sooth is dark; From the situation of the earth with respect to the and during another part of its course, the south pole sun, it necessarily follows that only one-half of its sur- is turned to the sun, and the north is cldark; and this is face should be exposed at a time to tile light and heat the cause of the difference of seasons, which will be diffused from that body. This is the case with all the better understood by referring to the subjoined figure. planets. When any one part of the earth is presented to the sun, it is day at that part, and all the other THIE SEASONS. heavenly objects are lost in the blaze of the great lumini- Let S represent the sun, and A B C D the earth at nary. When, on the contrary, any part is averted from various places of its annual circuit; when the earth is the sun, it is dark at that part, and the light of the at B or D, these are the periods of the equinox, when stars is allowed to tell upon our organs. Eachi part is the line of the equator intersects or cuts through the thus brought once every twenty-four hours towards the line of the ecliptic. At this period one half of the globe sun; in short, this is the cause of what we familiarly is illuminated from pole to pole, or there is over all the know as cday and night. earth an ecqual clday andc night of twelve hours. But There is a minute difference between the civil or legal day and what is called the sidereal day. The entire orb of the earth, in reality, revolves in 23 hours 56 minutes 4 seconds, or 3 minutes 56 seconds less than 24 hours. This is called a sidereal day, because the earth is then in the same relation to the stars as it was the day be- A fore. The fixed stars are so immensely distant from our - earth, that its whole orbit is in respect to them but a I! point; so that no sensible difference is produced by its revolving round the sun. But the sun being much nearer us, any inovemnent made by the earth can be T appreciated. Thle time which elapses firom the sun's being on the mneridian of any place to its returning to the same spot niext day, is exactly 24 hours, and is called an astronomical day. The natural day would always be the same as the sidereal day, if the earth had Illustin of te en. no other mnotion than tihat upon its axis. But in the when tile earth has proceeded to A, the pole or axis same time that it has performed one of its daily revo- still keeping the same position, or pointing to one parlutions eastward, it haIs also advanced about a degree ticular place in the starry heauvens, it will be turned westward, or in the opposite direction, which is the more directly from the sun; a greater proportion course it takles round the sun; so that before thle sun of his rays will shine oi any particular spot of the can shine exactly upon the same meridian, the earth southern half of the globe, nid the period of day, or must make up, as it were, its lee-way, and this it does sunlight, will exceed that of darkness by the proportion in 3 minutes 56 seconds, the difference of time between of tile lilght and shade parted in the circle of the earth. a snatu'ral and a sidereal dclay. If the earth, then, had It vwill be observed elso, that within the circle of the no other than its diurnal mnotion, we should have 366 south pole, the sun will shtine continually as the earith cldays in the year. revolves on its axis; or, in short, to the inhabitanis of WVhen any spiot on earth comes directly opposite to that part of the globe the sun will never set for several the sun, it is noon at that spot, and at every place in months. iThien the:earth hasp proceeded on to D, onethe same longitude. At the same moment it. is an half of its annual course is finished, or this is the spring hour before noon at the meridian of lonitule fifteen equinox, or equal cday and night. At C, anuain, the degrees to the, west of the same spot, and an hour ear- earth has arrived at our longest clday in summner, when lier for every fifteen degrees farther to the west; be- the axis is turned to the sun, and the resoions around cause, as the earth mioves from west to east, it requires the pole are in the light for a greater period, while so much time to bring those places to the samie point —- dclarkiness, or night, prevails for a less. It will be seen, namely, opposite to the sun. In like nainner it is an too, that nonw the pole and circle arouncd it revolve in hour after noon for every fifteen degrees to the east- perpetual light; or to the inhabitants of that region ward of the spot where it is noon, because at those the sun never sets for some inonths, but they have one places the sun has already been for so many hours past continued mtid uninterruptecl clday. At the other; or meridian. Thus the hour of the day varies in every south pole, the same chang es takie place, only matters part of the globe where the longitudle or meridian line are reversecd-there it is summer while we have'winter, is different. When it is twelve o'clock noon with us and the winter of the north pole is the summer of the in any particular part in Britain, it will be twelve south. In the middle regions of the earth, or around o'clock at midnight in a corresponding point on the the equator, the sun's place does not suffer a very great opposite side of the globe, near New South WVales; and change; and accordingly there the heat is nearly of the the intermediate hours, sooner or later, will all lie in same intensity all the year through; and the length the countries between these two points, exactly accord- of their days and nights is nIlearly equal, or nearly the ing to their position or degrees of longitude., same as at the periods of the equinoxes. But the orbit The earth is at a mean distance of 95,000,000 of in which the earth travels round the sun is not an miles from the sun, anid performs its revolution round exact circle; it is, as we have already mentioned, anm him in a sidereal year, which is 365 days 6 hours 9 ellipse, andc the sun is placed near one end of it, as at minutes 11 seconds mean solar time. The earth tra- the small circle and letter S. In consequence of this vels at the rate of 68,000 miles per hour. Its orbit is, circumnstance, the sun is much nearer us at one period as already stated, not a circle, but an ellipse, the sun of the year than another, and this happens in our win, 12 ASTRONiOMY. ter; accordingly, the sun appears about one-thirtieth creases. This may be rendered very plain, by suppospart larger ii. January than in'June. But in propor- ing that two persons placed individually at the end of a tion as the earth approaches in her orbit to the sun, her straight line, look at a candle removed at, say, 100 motion is quickened, and she passes over the winter yards' distance from them. It is evident that the half year in nearly eight days' less time than the sum- burning body will appear to be projected upon the wall mier. It is principally from this circumstance, as well of an apartment, or any other background, at very difas the shorter period of the day, that although the sun ferent positions to each of the spectators. The angle be nearer us in winter, and consequently his power of which this difference of position makes is similar to imparting heat greater, yet the actual quantity imparted parallax. The farther they remove from the light, is, on the whole, minuch less in the one season than the allowing them still to remain at the samne distance firom other. We have said that the north pole of the earth each other, the n more obtuse the angle would become, always points to a particular. spot in the heavens; this and the less the parallax. Thus the fixed stars, being is not, strictly speaking, correct; the pole or axis mcakes so far removed firom us, when viewed firom any two a circle round the centre of the axis of the ecliptic in a positions upon the earth's surface, are seen at the same long period of years, and it is this motion that gives place upon the celestial sphere, and hence have no perrise to the precession of the equinoxes, which will be ceptible parallax. It is different, however, with the afterwards described under that title. luminaries belonging to our system; and by this means astronomers have been enabled to estimate the quantity ABERIATION OF LIGHT. of space which separates us from them. For a comnAlthough the most convincing proof of the earth's plete account of the means by which this is accomorbitual motion is not to be found in any circumstance plished, we must refer the reader to more elaborate of which the senses can take immediate cognisance, but treatises than the present. A general and correct is afforded by the full development of the planetary enough idea of it may be formed from the familiar exsystem, there is, however, one direct proof of. it in a ample we have given. In the samne manner, suppose phenomenon discoveredby Bradley, an illustrious astro- two observers, one in the northern, the other in the nomer. It is called the aberrsation of ligqht, and is mani- southern hemisphere, at stations on the same meridian, fested by a small difference between the apparent and observe on the same day the meridian altitudes of the true places of a star, occasioned by the motion of light sun's centre.'-Haying thence derived the apparent combined with that of the earth in its orbit. Vision, zenith distances,' says Sir J. Herschel,'and.cleared it is well known, arises from rays of light proceeding them of the effects of refraction, if the distance of from any object, and entering the eye; and we see thei the sun were equal to that of the fixed stars, the sum object in the direction in which the rays have come. If of the zenith distances thus found would be precisely both the body giving forth light, and that one which re- equal to the sum of the latitudes north and south of ceives it, be at rest, the former will be seen in its true the places of observation; for the sum in question place, at least in so far as aberration is concerned; but would then be equal to the'meridional distance of let either of the bodies move, and this will not be the the stations across the equator. But the effect of the case. In order to render this plain, suppose a shower parallax being in both cases to increase the apparent of hail to fall perpendicularly upon a nsum ber of tubes zenith distances,'their observed sum will be greater -say the pipes of an organ; if the organ remniain sta- than the sum of the latitudes by the whole amount of tionary, the hailstones will descend sheer from the top the two parallaxes. This angle, then, is obtained by to the bottom, without any deviation right or left; but subducting the sum of the latitudes from that of the move the organ in any direction, and they will strike zenith distance; and this once determined, the horithe side opposite to the direction in which the motion zontal parallax is easily found, by dividing the angle is made. Now it is just in this way that the eye misses so determined by the. sum of the sines of the two latithe perpendicular ray, and meeting an oblique one, re- tudes.' It may be observed that the angles are deterceives an imnpression that the star lies in that direction. imined by means of very nice instruments. The paralThe object thus appears displaced, and the amouunt of lax thus obtained is called the daily or geocentric, in displacement is aberration. - The earth travels at the contradistinction to the annual or heliocentric, by rate of about nineteen miles per second, and therefore which, in general, is understood the difference of place is every instant changing its direction.. Time' is also of a heavenly body, as seen from the earth and from occupied by lighit in traversing space, which it does at the sun; in particular, however, it denotes the angle the amniazig sate of 192,000 siiles per second; so that formed by two lines from the ends of the diameter of also requires to be calculated for by astronomers. The the earth's orbit to a fixeld star, which, as we have effect of aberration is to mnake a star apparently de- already observed, from the immense distance of the scribe a small ellipse in the heavens, in the centre of latter, is inappreciable. Some idea of the imsportance which it would be seen if the earth were motionless. of parallax may be obtained from the fact, that before The reader must carefully distinguish between aberra- the sun's was determsined, the distance of that luminary tion and refraction; their effects are the same-namely, from us was not estimated at within 13,000,000 of miles to displace the ray-projecting object-but they proceed of its true amount. Its parallax is of course a very friom very dlifferent causes. [Besides these corrections minute cluantity, only 8".6. which astronomers have to nmake in their calculations, there is another, resultii fiom what is called paraEllax, OF SOLAR, SIDEREAL, AND ANOMALISTIC YEARS. which siay be as well introduced in this place. There are three different periods at which the sun may, in different senses, be said to return to the same PARASS -uAx..posi'tion-vhen he returns to the same equinox at which The wvord parallax, in its general signification, de- he was before; when he returns to the same point in notes change of place; but in astronomical boolks it his orbit, or the ecliptic; and when, being in perigee has a convenstional mnseaning, and implies the differenc (least distance fronm.the earth), or apogee (farthest disof apparsent positions of any heavenly luminary when tance from the earth), he comes back to either again; vievwed from the surface of the earth and fir'om its or, which is the same thing, when, havisg been at a given centre. The centre of the earth is the general station distance from any of these points, he returns to the to which all astronomicalo observations are referred; same point with respect to them. Each of these siiay the situation of a heavenly body, observed from the be said to be a conmpletion of the revolution of the sui surface of the earth, is called the apparent place; amd (strictly speahking, it is a revolution of our own earth that at which it would be seen from the imaginary place round him), and a revolution thus performed is called of observation at the centre of the earth, tihe tirue or a year. The first and shortest is the equinoctial, solar, szeanz place. Hence the altitudes of the heavenly bodies or tropical year; for his time of returning from tropic are depressed by parallax, which is greatest at the to tropic, they being situations holding the sanme relation horizon, and decreases as the altitude of the object in- to the equinox for the time being, is obviously the same CHAMBERS'S INFORMATION FOR THE PEOPLE. as that from equinox to equinox. The value of this June 15th, and September ist-the apparent is always year is 365 days 5 hours 49 minutes nearly. But later than the mean time, or the clock is before the although the earth has thus returned to the samne equi- sun; in the other intervals which complete the year, the nox, it has not made the entire circuit of its orbit, but reverse is the case, and the clock is after the sun. The must travel a little farther to arrive at the same point greatest difference between solar and true time amounts it was in a year before. This arises from a backward to between fifteen and sixteen minutes. Tables of equamovement of the equinoctial point, as previously ex- tion are constructed for the purpose of correcting the plained. The second is the sidereal year, which con- differences. For further information on the Measuresists, as we said before, of 365 days 6 hours 9 minutes ment of Time, see No. 18 of the present series. 9".6, reckoned in mean solar time, or a dcay more, reckoned in sidereal time. Here, then, there is a re-.THE MOON. markable difference between solar and sidereal time, Next to the sun, the moon is to the inhabitanlts of which requires explanation. If the reader will recollect the earth the most remarkable and important of all what was said with regard to a solar and sidereal day, the heavenly bodies. The mean horizontal parallax the discrepancy between the times of the years will of the moon is 57' 18"; and her mean distance from the become apparent. In the course of twelve months, all earth 236,947 miles. Like the sun, the moon advances the little daily deficiencies, as it were, amount to twventy- in the heavens in a motion contrary to that of the stars. four hours, which constitutes the difference between Notwithstanding the vast distance she is from us, it is the two years. The sun's apparent cannual motion among little more thans one-fourth of the. sun's dianmeter, and the stars is performed contrary to the apparent diurnal the globe of that mIagnificent luminary would nearly motion of the sun and stars; hence the stars gain every twice include the whole orbit of the moon! It has day three minutes fifty-six seconds on the sun, which various motions; as a secondary planet, it revolves makes them rise that portion of time earlier every day. round the earth, which is its primary. Along with the In the course of a year, the sun will fall behind the latter, it revolves round the sun, and it has a rotatory stars a whole circumference of the heavens, or one re- motion upon its own axis. Owing to the sun's apparent volution, which deficiency he must make up, to complete movement in the heavens being in the same direction the number of days in a year. It is evident, then, that with that of the moon, only slower, the latter has to the sun apparently, or the earth really, turns 366 times make up for that slowness in, the salne way as we have round upon its axis; and had it no other motion, there mentioned with regard to the earth, and the time it would be as many days in a year. After the earth or takes constitutes the difference between the sidereal sun has completed a sidereal year, before it can finish and synodic month or lunation. The sidereal month an anomalistic year, it must describe a farther arc of is 27 days 7 hours 43 minutes 11".5, in which time 11".8 to arrive at its original position in perihelion, the the moon performs a complete revolution rouend her latter having moved forward to that amount. In so primary; and the other is 29 days 12 hours 44 minutes doing, it occupies 4' 39".7, which must be added to the 2"'.87, the time which elapses between two new moons, sidereal period, making the anomalistic year 365 days or two conjunctions of the sun with the moon. It 6 hours 13 minutes 49".3 in length. All these pe- happens that its revolution upon its axis is performed riods have their uses in astronomy; but the one in in the same time as its revolution round the earth, so which mankinsd are most particularly interested is the that the same side of her orb is always presented to the tropical year, or that on which the seasons depend, and latter planet. Although the moos's rotation on her which is a compound phenomenon, depending chiefly axis is uniform, her motion in her orbit is not so, ancd and directly on the annual revolution of the earth we are by this means enabled at times to obtain a peep rounsd the sun, but subordinately also, and indirectly, of the equatorial portions of her eastern and western on its rotation round its own axis, sides. Her axis also is not perpendicular to her orbit, 1End a small part of each of her poles alternately becomes visible. These phenomena are known by the Although the sidereal day, from its uniformity, is well name of librcations of the moon, and they are of two adapted for astronomical purposes, yet it is scarcely distinct kinds, the result of different causes. sufficiently marked for the ordinary wants of life. No The wisdon. and beneficence of the Deity are strikperson but an astronomer ever attends to the culmina- ingly displayed in the econoney of moonlight, as distion of a star; on this account the diurnal return of tributed to our globe during various seasons of the the sun to the same meridian has been universally year. The remarkable phenomenon of the htarvest adopted as the measure of time; and this is called a mloon is familiar to every one. During the time that civil day. Most nations reckon the beginsting of their our satellite is full, and -or a few days before and after, day from midnight, but astronomers count from noon in all about a week, there is less difference between the to noon. The day thus determined is called the astro- time of her rising on any two successive nights, than nomical or solar day, and being regulated by the true when she is full in any othe mnionth of the year. By motion of the sun, the time which is measured by it is this msieans an immediate supply of light is obtained called true or apparent time. Two causes conspire to after sunset, so beneficial for gathering in the fruits of render astronomical days unequal: first, the variable ye- the seasons. To conceive of this phenomenon, it must locity of the sun in his orbit; and second, the obliquity be recollected that the moon is always opposite to the of the ecliptic. A muean astronomical day, which is in- sun when she is full; that she is fill in the signs Pisces dependent of any causes of inequality, has been obtained and Aries, these beingo the signs opposite to Virgo and by astronomers eintroducing into the system two ima- Libra, which the suns passes through in September and ginary suns. These two fictitious bodies are supposed October, our harvest months. Thus, although, whento move uniiformly, the first in the ecliptic, the second ever the moon enters the two former signs (and she in the equator; acnd as the circles are both equal, the does so twelve times in a year), the same circumstance actual motion of each of the bodies is equal. To those takes place with regard to the tilne of her rising; yet desirous of studying this part of the subject, we would it is not observed on these other occasions, just because recommend a perusal of the article Astrnosnmy in the she is not fdll at the time. The reasonlf there being seventh edition of the Encyclopcedia Britannica, page little differenlce in the time at which she rises on several 778, where it is well illustrated. The correction or consecutive nights is, that at these periods her orbit equation, by which apparent time is reduced to mean is nearly parsellel to the horizon. The harvest moons time, is technically called the eqzcations of tinme. There are as regular in south latitude as with us in north latiare only four cldays in the year when the apparent and tuder only they happen at different periods of the year. mean time are the same, and the equator of time niothing. In the interval between the first and second ECLIPSES. of these-that is, December 24th, and April 15th-and, Eclipses are caused by the positions of the earth and again, in that between the third and fourth-that is, moonl with respect to each other and to the sun. An 14 ASTRONOMY. eclipse of the sun takes place when the moon is between mutual attractions, so that it is undulated or waved, the sun and earth; and an eclipse of the moon is the thus, The number of undulations in a whole result of the earth being between the sun and moon. revolution is, however, onlly thirteen, so that the deIn other terms, the shadow of the earth cast upon the viation from the ellipse is exceedingly trifling. Jupimoon causes a lunar eclipse, and that of the moon upon ter, Saturn, and Uranus, are all attended by satellites, the earth causes a solar eclipse. as we have seen; and they form, as it were, each of The following figure explains an eclipse of the sun. the primaries with its attendant moons, a sort of miA B is the sun, M the moon, and C D the earth. The niature system, similar in the laws by which they are governed to the great system to which they all belong, where the sun may be termed the primary plaslet, and the primary planets the satellites. Their orbits are circles or ellipses of small eccentricity, the primary occupying one focus. Of these systems, that of which Jupiter forms the head has been studied with the -l g:reatest attention. The discovery of Jupiter's satellites shadow of the imoon falls upon a part of the earth's by Galileo, was one of the first fruits of the invention surface; and there, accordingly, the sun appears in of the telescope, and forms a renalrkable era in the eclipse, the body of te lI1n beinghistory of astronomy. From it resulted a solution of the heclipse, thae body of the mlsoon being placed between. great problem of the longitude, and the grand discovery Another *diagranm Arepresents can eclipse of the moon, of the velocity of light. It also established completely In this instance A B is the sun, C D the earth, while the Copernican system, and confirmed the laws of Kepler. The satellites of Jupiter revolve from west to east like our moon, but they are much less in comparison with C their primary than it, whilst their orbits are of smaller dimensions, and less inclined to the ecliptic of their'111 ),Itl primary than that of our satellite. The largest of them is about 3377 miles, and the least about 2068 miles in diameter. The satellites of Saturn have been mnuch less studied, and have fewer peculiarities. Those of Uranus, however, are remarkable, inasmuch as their orbits are the moon appears as a small circle (M) involved in the nearly perpendicular to the ecliptic, and in these orbits shadow thrown by the earth. they are supposed to have a retrograde motion-that The places of the earth's orbit and the moon's do not is, from east to wuest, instead of from nvest to east, like exactly coincide, but cross or intersect each other; and the other planetary bodies. No satisfactory cause for the consequence is, that in general the moon, when she this departure (if it be one) from the general rule can is in conjunction with the sun, either passes on one side be given. It is by accurate observation of the satellites or the other, and therefore does not intercept the sun's that the densities of the planets, or their Lmass as prorays, or produce nn eclipse. An eclipse of this kind portioned to their bulks, have been ascertained; as camn only take place when the earth and moon are in also, by watching their fiequent eclipses, that the veloconjunction in that part of their orbits which cross each city with which light travels from the heavenly bodies other (called the nodes), because it is then only that to the earth has been brought within our calculation, they are both in a right line with the sun. If the orbit of the moon were parallel to that of the earth, an eclipse PERTURBATIONS. would happen every month. Partial eclipses, again, The name of perturbationts has been applied to those are caused when the moon, in passing the earth, is not inequalities in the lunar and planetary motions which directly in a line with the sun, but a little on either arise fiom the -universality of attraction. Thus not side; the consequence of which is, the edge of one side only does the sun attract the earth, and the earth the of the moon onIly cips into the sun's disk. W5hen the mloon, but the latter attracts the prececling, and both sun is eclipsed, the total darkness is confined to one are again influenced in their movements by the great particular part of the earth, but the lunar eclipses can centre of the system to which they belong. Not only is be seen from every part of the earth, when the moon this the case, but every individual planet in the system is above the horizon; and both circumstances prove attracts, and is attracted by, all the rest, although that the earth is a good deal larger than the moon. The certainly in a very trifling degree when compared with moon arrives very nlearly at the same situation with that exercised by the sun over the whole of them. But respect to the earth, after making 223 revolutions, in those miniature systems —such as the moon and which are performed in eighteen years, of 365 days earth, Jupiter and his satellites, bc.-the perturbations 15 hours 7 minutes and 43 seconds each; so that, thus arising, though insensible in short intervals, beafter a period of about eighteen years, the series of come apparent when accumulated, and delanmge the eclipses recommences nearly in the same order; a cir- elliptic motions and relations. The calculation of the cunistance observed by the ancients. The mean number effects of these dist!urbing forces is famous in the history of eclipses which occur in a year is about foarm, and there of mathematical analysis, under the name of l'he Preoare sometimes as many as seven. There must neces- blem Qf the Ti-ee'Bodies. It is so worded, because the sarily be two solar eclipses, but it is possible that there Sun, Moon, and Earth, aiLd the Sun, Jupiter, and lmay not be even one lunar. A remarlkable eclipse, Saturn, form each separately a systemis little influenced called,in annular (or circular) solar eclipse, happenls by the rest. Anythiiig like an attempt to exhibit the when the moon, being in coljunction with the sun, the method by which these nice calculations are made, is edge of the latter appears for a few minutes as a nar- impossible in this place: of its difficulty, some idea may row ring' of light encircling all round the darlkldisk of be formed, when vwe consider, what is apparent to every the moon. A great solar eclipse, visible in England, one, that the bodies under investigation are continually will take place in M.arch 15, 1858, andl a still more shifting their relative distances from each other, and remarkable one, when the whole disk will be nearly altering the intensity of the disturbing force, which covered, in August 19, 1887. evidently must materially increase the abstruseness of the calculation. Yet great as the difficulty may be, THE SATELLITES. the effiect of these disturbances has been ascertained in The earth, we have seen, is attended in her annual many instances with the most rigid accuracy, enabling circuit round the sun by one satellite, the moon, which the astronomer not only to predict positions and revolurevolves round her as a centre. Strictly speaking, both tions with certainty, but to point, as in the case of the move round a common centre of gravity in an elliptic planet Neptune, to the heavens, and to pronounce that orbit, the regularity of which is disturbed by their there, in such a spot, would a planet appear to the 15 CHAMBERBS'S IINFORMATION' FOR THE PEOPLE. telescope of the observer. One of the principal effects the solar nstation. Its amount, however, is so exproduced on our globe by this play of gravitation is ceedingly small, as not to be appreciable by obserdenominated vation. That resulting from the moon's action, however, is sufficiently so, as to have been discovered by TIHE PRECESSION OF THE EQUINOXES. Bradley before theory had indicated its existence. Its The equinoctial points, we have already explained, period depends upon the revolution of the moon's are Aries and Libra, where the ecliptic cuts the equa- nodes, which is performed in 18- years, and in about tor. They are also termed nodes, and the line which that period of time the axis of the world describes a joins the two is called the line of the nodes. The small circle in the heavens, about eighteen seconds in longitudes of the stars, as has been also observed, are diameter, contrary to the order of the signs. This counted on the ecliptic from the vernal equinox Aries. apparent vibratory motion is denominated the nutation Now if the line of the nodes is invariable, the longi- of the earth's axis. The two phenomena of precession tude of the stars will of course remain the same from and nutation are intimately connected, or rather are age to age. But on comparing the actual state of constituent parts of the same phenomenon, and dethe heavens with the recorded observations of ancient pendent upon the same cause, as noticed above under astronomers, it is perceived that the longitudes of the Precession. It is impossible here to enter more mistars have considerably increased; so that, to explain nutely into the subject, or explain it more in detail. the circumstance, we must either suppose that the For an admirable account of it, we refer the reader to whole firmament has moved in the order of the zodiacal Herschel's Treatise on Astronomy, p. 333. We also signs, or else that the equinoctial points have gone would direct the inquirer to the same admirable work backwards, or retrograded westward; since these points for further information upon the subject of perturbadepend entirely upon the motion of the earth, which tions, comprising all the complicated varieties of motion. was far more likely to be disturbed by some cause or In general, they may be said to arise from the play of other, than that the countless multitude of stars should attractions kept up by the whole of the planets amongst have a motion relative to these points. Accordingly, themselves, they with the sun, and the sun with them; the phenomenon lhas been explained, by attributing to the distances of the bodies from each other, which are them a retrograde motion from east to west, in conse- always varying; and the masses of matter, and the quence of which the sun arrives at them sooner than shape of the bodies, which are invariable. In concludif they had remained at rest. Hence the equinoxes, ing this part of our subject, we may remark that it is spring and autumn, and the other seasons, happen by means of the perturbations of those planets which before hlie has completed an entire circuit. This motion, have no satellites, that astronomers have arrived at a however, is extremely slow, amnounting only to a degree knowledge of their masses. Every planet produces an in about seventy-six years; so that the equinoctial amount of perturbation in the motions of any other, points will take nearly 26,000 years to make ass entire proportioned to its iasss, and to thIe degree of advantage revolution of the heavens. This motion was known in or purchase which its situation in the system gives it very ancient times, and its discovery is ascribed to over their movements. Hipparchus, who lived about 140 years before Christ. The consequence of this retrograde movement is, that STABILITY OF THE SYSTEI. the sun's place amongst the zodiacal signs, at any It -is natural to inquire whether the nunerous perseason of the year, is greatly different from what it turbations which all the heavenly bodies are subject to, formerly was. The vernal equinox now happens in the are such as, in the long-run, to overthrow the present constellation Pisces; the summer solstice in Gemini; arrangements of the System. If any cause were at the autumn equinox in Virgo; and the winter solstice work to diminish steadily the mean distance of a in Sagittarius. Astronomers, however, still count the planet, it must of course ultimately fall into the sun. signs from the vernal equinox, which always corresponds It has, however, been proved that the total effect of all to the intersection of the ecliptic with the equator; and the mutual disturbances has no such tendency, and on this account it is necessary carefully to distinguish that the planets and satellites may revolve for countbetween them. less ages, without any radical change happening to tIhe The cause of precession is to be found in the com- character of their orbits; they will preserve both their bined action of the sun and moon upon the protuberant mean distances and the average shape of their ellipses. mass of matter accumulated at the earth's equator, the The only thing that remains under any suspicion as attraction of the planets being scarcely sensible. The a means of bringing about a decay in the System, is attracting force of the sun and moon upon this shell of a resisting. medium: that is, if the planetary spaces, matter is of a twofold character; one is parallel to the instead of being perfectly blank and void, are filled equator, and the other perpendicular to it. The ten- with a very thin gas or ether that would impede tihe dency of the latter force is to diminish the angle which motion of bodies, as our own atmosphere resists any the plane of the equator makes with the ecliptic; and body that is impelled through it. It is at present were it not for the rotatory motion of the earth, the doubtful whether such an ether exists; it is certain planes would soon coincide; but by this motion the that, if it does exist, it is exceedingly rare, and cannot planes remain constant to each other. The effect pro- produce any sensible effect in less than thousands of duced by the action of the force in question is, how- years. Still, if it exist at all, it must tell some time or ever, that the plane of tie equator is constantly, though other, and will have the effect of lessening the mean slowly, shifting its place in the mamnner we have en- distances, and contracting the orbits, so that an end deavoured to describe. to planetary revolution must be the inevitable consequence. It has been suggested, on the other hand, as NuT-~TIO~'. ~ ~.NUTATION. probable, that the planetary periods may coontinue to The action of the sun and moon in producing pre- diminish for thousands of years yet to come, then cession is various, at different periods of the year, ac- reach a limit, and afterwards gradually return to their cording to the relative distance of the earth from them, former- periods of revolution. This progressive and Twice a year, the effect of the sun in producing it is retrograde, or oscillatory kind of motion, is by no nothing; and twice a year-namely, at the solstices- means uncommon in nature, a noted example being it is at maximum. On no two successive days is it found in the magnetic needle, which seems to oscillate dlilke, and consequently the precession of the equinoc- between 23 degrees west and 23 degrees east of due north tial points must be unequal, and the obliquity of the in the course of several hundred years. It is expected, ecliptic subject to a half-yearly variation; for the sun's however, that the question of a niedium i will shortly force, which changes the obliquity, is variable, while be decided by a more rigid and extensive study of the the rotation of the earth, which counteracts it, is con- comets, which are so light, and so much spread out, stant. By this means the plane of the equator is sub- that the slightest resistance would soon show itself in ject to an irregular;.otion, which is technically called contracting their orbits. 16 GE OL O GY. GEOLOGY (from the Greek g6, the earth, and logos, dis- land and rocky heights, was once loose material beneath course) is that science which treats of the materials the waters; and seas now roll their waves over the surcomposing the earth's crust, their mode of arrange- face of ancient continents. Nor is there any cessation ment, and the causes which seem to have produced of this alternating process: a little shifting of the that arrangement. By the earth's crust is meant that theatre of activity, periods of greater or less intensity, external shell or covering of solid matter which is ac- and a progress in vital development, are the only cessible to man's investigation; the term being used diversities which mark the onward operation of these in contradistinction to the interior mass, respecting the ever-modifying causes. As they are the prime sources nature and composition of which we can know nothing of all geological phenomena, so a knowledge of their by inspection. Thin as this crust may seem, it never- power and mode of action forms the basis of all true theless presents innumerable objects for investigation; geological knowledge. hence the magnitude of the science, which has been ranked in point of importance second only to that of CAUSES MODIFYING THE EARTH'S CRUST. astronomy. The materials which constitute the crust of the globe are exceedingly varied; but whatever their These causes chiefly resolve themselves into degradcomposition, origin, or aspect, they are known by the ing and elevating; that is-whether they be mechanical, name of rocks. It is with rocks and rock-formations chemical, or vital in their nature-their effects mainly which the geologist has to do; arrange and classify tend to raise or to depress certain portions of the earth's them, discover their origin, treat of the organic remains crust beneath the surface-level of the ocean. imbedded in them, and thus arrive at some conclusion as to the phases which our planet has assumed during Degrading Causes.-These refer to the wearing down their formation. Geology, therefore, in its widest sense, of the elevated portions of the earth's surface, and the includes physical geography, which limits itself to the transport of the materials to lower levels. The disinmere surface configuration of the earth, as occupied tegration is brought about by certain mechanical and by land and water, mountains and valleys, and other chemical forces, and the carrying down into low levels external appearances; lithology, which refers to the is, in the main, a result of the law of gravitation. Concomposition, order, and relation of the rock masses sidering that the solid parts of the earth are in their composing the crust; mineralogy, which treats of the very nature liable to the operation of these forces, it individual crystals, or mineral elements, of which rock appears quite unavoidable that land should be demasses are composed; and oryctology, or palarontology, graded. The causes of this degradation may be conwhich directs itself exclusively to the consideration of sidered under three heads-meteoric, or those connected the fossil plants and animals that may be found im- with the atmosphere; fiuviatile, or those depending on bedded in the rocky strata. In the present sheet, we the action of rivers; and oceanic, or those in which the shall endeavour to exhibit an outline of the lithology, sea is the immediate agent. or rocky structure of the globe, embodying therewith The operation of the atmosphere and its vapoury an account of the fossil remains characteristic of the contents upon the land proceeds in two ways-chemical successive steps or formations of that structure; this and mechanical. There is a tendency in the hardest we may designate descriptive geology. Economic geo- rock to absorb oxygen and carbonic acid from the logy, as concerns minerals and metals, physical geo- atmosphere, and to be by that union dissolved. And graphy, and the other subordinate branches, will form this is a union which is always occurring, though in the subjects of separate treatises. some places with more conspicuous results than elseIt is necessary, however, before entering upon any where. If the soil on any hill of volcanic rock be exaanalysis of the materials of the earth's crust, to ex- mined, we shall first find a fine powdery earth, then a amine the causes which have determined, and which mixture of earth and splinters of rock, next splinters still continue to determine, the formation and arrange- alone, graduating into the hard rock below; and such ment of these materials. We know that some rocky may be considered as an exhibition of the gradual masses are hard and crystalline, others loosely aggre- process by which any rock is disintegrated into soil gated and earthy; the merest tyro can distinguish be- under the action of the atmosphere. In Jamaica, tween granite, marble, sandstone, and coal, which all this disintegration of volcanic rock has taken place to differ in composition, and maintain different positions a great depth. In granite, which is considered the in the crust: some rocks appear always in strata or most durable of all rocks, one of the component sublayers, others in irregular masses, without any determi- stances (felspar) has a great tendency to be decomnate arrangement; the petrified remains of land plants posed; hence even this rock is sometimes found to and animals are found imbedded in some layers, those have been reduced to gravel or powder to a considerof marine animals in others, while many are utterly able depth. A hollow way, blasted through granite, destitute of such reliquire. What, then, are the grand was found in one instance to have been in six years causes for this variety and arrangement of material? pulverised. to the depth of three inches. These are Rocks have no inherent vitality, like plants and ani- solely chemical phenomena. mals; they cannot add to their material, or transport Again, water percolates through minute fissures in themselves from place to place; they are inert, lifeless rocks. When frost arrives, the water freezes and swells, masses, subject in every respect to the physical laws of and thereby dislodges parts of the rock, which are the universe. Obeying the laws of attraction and gra- precipitated into lower levels. Or it may meet some vitation, acted upon by electrical and chemical agencies, clayey veins or strata, hitherto sufficient to keep various worn down by the mechanical effects of winds, frosts, masses together: these veins or strata, being gradually rains, and rivers, borne seaward and strewn in layers softened by the water, lose their power of cementing beneath the waters, and upheaved again by earthquakes the masses; and the upper then fall away or slide into and volcanoes-they are ever being displaced and re- a lower level. A slide of rock from the Ruffiberg, in formed, each new formation of material enclosing some Switzerland, in 1806, filled the bottom of the vale relic of vitality, which becomes the test anid type of below, destroying many villages, and causing the loss the earth's conditions during the period of its enclo- of 800 lives. The impulse of wind and rain on the sure. Here the ocean encroaches upon the land, there surface of rock is also of great efficacy in pulverising new land emerges from the ocean: what is now dry and wearing it down, sharp points being rounded, and No. 2. 17 CHAMBERS'S INFORMATION FOR THE PEOPLE. soft parts hollowed. In Sweden there are some large mouths of rivers, the delta of the Ganges is 220 miles detached masses of granite, containing perforations pro- in one direction by duced by this cause, some so very large, as to admit of 200 in another. a horse and cart passing through them. These effects The matter carmay be considered as chiefly mechanical. ried down by rivers, When water collects into channels, and follows its and thus deposit- well-known tendency to find the lowest level to which ed, is nothing in it has access, it becomes a mechanical instrument of amount compared still greater force for wearing down the land. In its to that transported e f1 smallest rills, as it descends the mountain side, it cuts to the ocean. The into the soil, and carries off whatever particles it can quantity of sand disengage. When gathered into brooks, its operations and mud brought - are still more powerful. When one of these is placed down by the Gani- a_ amongst rmountains, every heavy shower swells it into ges to the Bay of an impetuous river, by which large quanttiies of de- Bengal, is in the -i tached rock and soil are brought down. In the upper floodseasonso great, parts of the courses of almost all rivers, the greater that the sea is discoloured with it sixty miles from the speed of descent makes up for the smaller volume of river's mouth. Mr Lyell estimates the quantity of water, as far as the power of bringing down stones and solid matter brought down by this iiver every day as soil is concerned. Again, in the lower part of the equal in bulk to the greatest of the Egyptian pyramids course, the smaller speed is sometimes compensated by According to Lieut.-Colonel Sabine, the muddy waters the unevenness of the course; in which case the water of the Amazon river may be distinguished 300 miles is incessantly driven from one projection of the banks from its embouchure. against another; and by that means wears away a great The constant action of the sea upon the land is strikquantity of solid matter. The mere flowing of pure ingly apparent to the inhabitants of coasts. Whole water would exert little influence on hard rocks; but islands have been destroyed by the action of tides, all rivers carry down sand and gravel according to their waves, and oceanic currents, while the remains of others velocity;* and these, by rubbing and striking against rise above the surface of the water like the ruins of the sides and bottoms of the channel, assist in scooping some desolated city. Many instances of the encroachout gullies and ravines, which everywhere present ther- ment of the sea upon the land have been recorded. selves. The Nerbuddah, a river of India, has scooped An inn on the coast of Norfolk, built in 1805, then out a channel in basaltic rock 100 feet deep. The river seventy yards from the sea, was, in 1829, separated Moselle has worn a channel in solid rock to the depth from the coast by only a small garden. A church on of 600 feet. Messrs Sedgwick and Murchison give an the coast of Ient, which, in the reign of Henry VIII., account of gorges scooped out in beds of the rock called was a mile inland, is now only about sixty yards from conglomerate, in the valleys of the Eastern Alps, 600 the water's edge. The island of Nordstrand, on the or 700 feet deep. A stream of lava, which was vomited coast of Schleswig, was, in the thirteenth century, fifty from Aitna in 1603, happened to flow across the channel miles long and thirty-five broad. About the end of of the river Simeto. Since that time, the stream has the sixteenth century it was reduced to an area of cut a passage through the compact rock to the depth of only twenty miles in circumference. The inhabitants between forty and fifty feet, and to the breadth of be- erected lofty dikes for the purpose of saving their tertween fifty and several hundred feet. The cataract of ritories; but in the year 1634 a storm devastated the Nimagara in North America has receded, according to whole island, by which 1340 human beings and 50,000 most authorities, nearly fifty yards during the last sixty head of cattle perished. Three very small islets are years. Below the Falls, the river flows in a channel all that now remain to point out the place where once upwards of 150 feet deep, and 160 yards wide, for a flourished the fertile island of Nordstrand. distance of seven miles; and this channel has mani- It thus appears that there are causes in continual festly been produced by the action of the river, operation for the wearing down of the elevated parts of Sometimes, duringfloods, rivers produce great changes the earth's crust, and taking the component particles in very short periods. A flood caused by the bursting into lower levels. The effects of these causes may be of the barrier of a lake in the valley of Badness, Swit- easily traced in the aqueous rocks, many of which are zerland, moved at first with the tremendous velocity of simply deposits of sediment carried by water from high thirty-three feet per second. From the barrier burst into low places, and subsequently hardened, probably by the waters to Lake Geneva, there is a fall of 4187 by heat from below and pressure from superincumbent Paris feet; the distance is forty-five miles; and the materials. Were such causes not in some way counwater flowed over all this space in five hours and a- teracted, dry land could not long exist; all would be half. It carried along houses, bridges, and trees; and taken down and buried in the sea-our planet being masses of rock equal in size to houses were transported reduced to a plain spherical mass. WVe find the couna quarter of a mile down the valley. teraction in certain forces incessantly tending to elevaThe matter carried down by rivers is often deposited tion of the superficial rocky crust. at their sides, when it constitutes what is called alluvial land. Sometimes it is deposited at the bottom of lakes, Elevating Causes.-As degrading forces are chiefly when it forms what are termed lacustrine deposits. In owing to water, so those of an elevating character are many instances it has been deposited in large quan- chiefly owing to fire. They are therefore sometimes tities at the mouths of rivers, giving rise to alluvial comprehended under the term Igneous Agency. flats, which, from their resemblance in shape to the The manifestations of igneous agency at present obGreek letter A, have been denominated deltas. The servable may be considelredunderthree heads-namely, triangular form of a delta, like that of the Nile (see volcanoes, earthqualkes, and gradually - elevating forces. fig.), for example, is produced by the river at a certain These phenomena may be viewed as the effects of subpoint inland dividing itself into two main streams, terranean heat, operating under different circumstances. which gradually diverge till they reach the ocean, A volcano may be described as an opening in the earth's enclosing the space which constitutes the delta. As an surface, bearing the general appearance of a vent of instance of the vast extent of new land formed at the subterranean fire, and through which smoke, cinders, * It has been calculated that water running with a force of and ashes are almost continually issuing, but which 3 inches per second will tear up fine clay, 6 inches will lift fine sometimes discharges great fragments of rock, and vast sand, 8inches sand ascoarse as linseed, and 12 inchesfine gravel; quantities of melted rocky matter, or lava. The gewhile it requires a velocity of 24 inches per second to roll along neral effect is a throwing up of earthy material, in a rounded pebbles an inch in diameter, and 36 inches per second conical form, from a low to a high level, as represented to sweep forward angular stones of the size of a hen's egg. in the following view of Mount ]Etna. 1 8 GEOLOGY. Geographers at present reckon about 200 volcanic about six miles long and four broad, contained, a few vents in activity throughout the earth. The greater years ago, three volcanic isles, the first of which rose number of the whole are in a line along the west coast about the year 200, the second in 1650, and the third of South and North America. There are many in the in 1709. In a part of the bay where the water is geneislands of the Pacific and Indian Oceans, and in the rally several hundred feet deep, a shoal has for several central regions of Asia. In Europe, there are only years been gradually rising: about 1816 there were three in great activity —]Etna in Sicily, Vesuvius in fifteen fathoms water upon it; in 1830 there were only Italy, and Hecla in Iceland. But a vast number of three or four; and later accounts reduce it to two and hills throughout France, Britain, and other countries, a-half fathoms. This rising mass was ascertained to be bear the appearance of having once been active vol- of solid rock, about half a mile in length by one-third canoes. As volcanic action often takes place in the of a mile in breadth; the water deepening suddenly bed of the sea (submarine volcanoes), and as there are all round it. probably many on land not yet described by geo- Many islands which have long been inhabited by graphers, the number of such vents throughout the man bear all the appearance of having risen in like earth must be considerably more than two hundred. manner, from the bosom of the deep. The islands of St Helena and Ascension, the Azores, the West India islands, Iceland, and many of the islands in the Pacific, -'-~:~ — ~ -........are evidently the produce of volcanic action.' Owhya- *~ ~'~~ ~~~-'- ~ ~ —-~~~ ba~hee,' says 1M. de la Beche,'is a magnificent example __-___ e d ~~~' -~ ~~of such an island: the whole mass, estimated as expos____i_' _________ _ --- - ing a surface of 4000 square miles, is composed of lava, or other volcanic matter, which rises in the peaks of ___________ _______________ Mouna Roa and Mouna Kaa to the height of between 15,000 and 16,000 feet above the level of the sea.' The causes of earthquakes have not as yet been satisfactorily explained, but they are now generally allowed to be connected with volcanic agency. They occur less frequently, and generally with less tremendous effect, in Europe than in some other parts of the world-those F131 ~ ~ ~ ~ ~ parts where volcanic agency is most active being also the parts where earthquakes are most frequent and most dreadful. Though their effect is sometimes to =; -—,~ ___~~ cause a sinking of the ground, they may, upon the - A7 ~J~-~ ~ ~i~ ~~?::-zi< ~ whole, be considered as among elevating causes. It is conceived that they are produced by gases confined in the molten interior of the earth, similar to those which Of the power of volcanoes to throw up large quan- find vent by volcanoes. Such gases, prevented by local tities of solid matter we have many examples. During circumstances from escaping, may, it is thought, thus an eruption of ]Etna, a space around the mountain, shake the solid ground over a large tract, and even 150 miles in circumference, was covered with a layer cause it to rise to a certain extent above its former of sand and ashes, generally about twelve feet thick. level. The most striking proof which has been adduced In the first century, the cities of Herculaneum and in support of this doctrine is the effect of the earthPompeii were buried beneath such a layer of matter by quake which took place in Chili in 1822. This is part Vesuvius. In 1660, the philosopher Kircher, after of that continent in which volcanoes are most numeaccurately examining ]Etna, and the ground adjoining rous and active. On the occasion referred to, a shock its base, calculated that the whole matter thrown out was felt along the coast for more than 1000 miles. The by it at its various active periods would form a mass land for 100 miles along the coast, and backwards to twenty times as large as the mountain itself, which is the line of the Andes, was raised above its former level. 10,870 feet high, and thirty miles in diameter at the At the shore, and for some distance along the bottom base. From this mountain, in 1775, there issued a of the sea, the rise was three or four feet; so that rocks stream of lava a mile and a-half in breadth, twelve formerly submerged, and covered with shell-fish, were miles long, and 200 feet thick. At an earlier period, now exposed above the sea. Old beaches, similar to there was a stream which covered eighty-four square that now raised, have also been observed in parallel miles. In 1538, a large hill, since named Monte lines along the coasts of Chili and Peru, ranging, Nuovo, was thrown up in the neighbourhood of Naples according to Mr Darwin and M. Von Tschudi, from in one night; and in 1759, in a district of Mexico pre- 20 to 120 feet above the ocean. viously covered by smiling plantations, a sudden out- It has since been observed that old beaches, similar burst of volcanic action, which lasted several months, to those in Chili, exist in the neighbourhood of many terminated in leaving six hills, varying from 300 to seas. Along the Firth of Forth in Scotland there is 1600 feet in height, above the old plain. one very conspicuous about forty feet above the present Of the effect of submarine volcanoes some interest- level of the sea, and which generally appears as a kind ing observations have been made in recent times. In of bank a few hundred yards back from the present June 1811, an island was thrown up by volcanic agency shore. In the Firths of Clyde and Cromarty, and innear St Michael's in the Azores. Columns of cinders deed in every place along the British coasts favourable rose 700 or 800 feet above the surface of the sea, with for their preservation, similar beaches, from twenty to a noise resembling that of distant artillery. In the several hundred feet above the present sea-level, can course of a few days the island was a mile in circum- be traced. They may always be detected by their terference, and about 300 feet in height, having a crater race-like level, and by the presence of rounded pebbles, in the centre full of hot water. Some time afterwards gravel, sand, and in some instances sea-shells, such as it disappeared. In July 1831, a similar island was usually compose beaches at the present day. In some thrown up, under precisely similar circumstances, in places old beaches have been conspicuous enough to latitude 37~ 11' north, and longitude 12~ 44' east, off become objects of popular wonder. In the vale of the coast of Sicily. It consisted of stones, mud, and Glenroy in Inverness-shire, as also in some neighcinders, and was of circular form, about a mile and bouring vales connected with G(lenroy, there are three a-half in circumference, with a crater of hot water in terraces along the sides of hills, at the successive the centre 400 yards in diameter. This island, named heights of 872, 1085, and 1165 feet, which the ignorant Sciacca, or Graham's Island, existed so long above the people of the district firmly believe to have been sea, as to allow of many persons landing upon it. The roads formed by the hero Fingal for hunting, but which Bay of Santorin, in the Greek Archipelago, which is are now shown pretty clearly to have been the shores 19 CHIAMBERS'S INFORMATION FOR THE PEOPLE. of quiet estuaries or arms of the sea, similar to many have gone to compose those that followed, and so which still exist in the Scottish Highlands. Among on in succession, to the present age. The series of the Alps, in Spain, France, Norway, in North and rocks formed during any one era must present certain South America, and indeed in almost every region differences characteristic of that era, whether it was which has undergone a narrow inspection, there are one of comparative quiet or of volcanic disturbance, vales marked in exactly the same way as Glenroy. and whether it was distinguished for exuberance or The existence of a force which gradually elevates the comparative destitution of vegetable and animal life. land in many places out of the water was discovered Again, just as at present fresh-water deposits differ by Mr Lyell. His chief observations were made upon from marine, so must rocks formed in lakes and estuthe shores of the Gulf of Bothnia, which he ascertained aries differ from those deposited in the ocean; and as to have risen several feet in the course of the last cen- different climates are peopled by different kinds of tury, and a few inches even since 1820. plants and animals, so in time past the rocks formed Besides the greater elevating causes arising from in hot regions must contain organic relics, differing subterranean fires, there are some lesser ones of less from those deposited under colder influences. Assisted mysterious origin. The sands deposited on beaches by these and similar tests, geologists have been enabled are sometimes blown by winds in upon the land, cover- to arrange the rocks composing the earth's crust into ing the vegetable soil throughout a large space, and in formations, systems, and groups-these divisions, both some instances forming hills of considerable height and in point of mineral composition and fossil remains, premagnitude. Some parts of the coast of Holland are serving so wonderful a persistence, that the groups of thus fenced with ranges of sand-hills, the whole mass the one hemisphere can be identified with those of the of which has been blown back from the sea. On some other. Let us detail this arrangement. parts of the French coast, large tracts, once smiling Passing the surface soil, and proceeding downwards to with cultivation, are thus buried under a sterile layer the greatest known depth, the solid crust may be said of sand, which is continually advancing, notwithstand- to be composed of two great classes of rocks-those ing every effort of man. On the coast of Moray, in the arranged in layers, and those occurring in irregular north of Scotland, a district once forming the barony of masses; in other words, the STRATIFIED and UNSTRATICulbleen, has been transformed into a sandy tract since FIED. The stratified are those which have been formed the fifteenth century. from deposition in water; hence they are also known In various parts of the world new land is elabo- by the terms aqueous and sedimentary. The unstratirated by the efforts of coral polypes. The works of fied are those which have been formed by fire, and are these creatures are seen upon a vast scale in the Pacific, also known by the terms igneous and volcanic. The where whole ranges of islands are formed by them. merest beginner can have no doubt respecting this first On the coast of New Holland there is a coral reef great division: we see the material now borne down to which stretches out to a thousand miles in length. The our lakes and seas arranged in layers or strata, while insects do not commence their laborious operations at a the matter ejected by volcanoes flows and consolidates great depth below water; from 60 to 100 feet is con- in no determinate order. The following engraving residered the utmost extent to which the coral extends presents the appearance which the stratified and undownwards. Many of these islands are of a circular or stratified rocks present in a section of the earth's crust. oval shape; hence the opinion that corals build upon the rims and in the craters of submarine vdlcanoes. The outer wall of the building emerges first above the waves, enclosing a pool of tranquil water. The seeds of vegetables are either brought there by sea-birds, or wafted by the ocean, and the islands soon become clothed with a mantle of green. The substance of,i t- i which these islands and reefs are composed is lime, i111 which the insects secrete from the sea-water, and A \ cement together with a glutinous matter contained in Unstratified. Stratified. their bodies. Mr Lyell, while surveying the Isthmus of Panama, detached a quantity of these animals, and Reverting to the stratified division, the geologist finds placed them on some rocks in a shallow pool of water. them consisting of various materials, variously conOn returning to remove them a few days afterwards, solidated and crystallised, variously impregnated with he found they had secreted stony matter, and had metallic substances, and characterised by different refirmly attached themselves to the bottom. (See mains of plants and animals. Here he finds sand and ZOOLOGY, p. 190.) To such organic agencies of eleva- gravel, there clay and boulders; in one place chalk, in tion as the coral animalcule, may be added the growth another coal; here marble, there roofing-slate; and so of shell-beds, the formation of peat, and other accumu- on in vast variety. He observes, besides, a certain order lating vital forces which contribute to the solid mate- of supraposition, notwithstanding that the igneous rial of the earth's crust. rocks have often disturbed the regularity of the stratiIf we consider the operation of the elevating causes, fled, and broken them up into inclined, contorted, and we can be at no loss to understand how we should now confused positions. On these grounds, the stratified see, as composing dry land, and sometimes in very lofty rocks have been arranged into formations, systems, situations, strata which were once at the bottoms of series, and groups. Thus the term formation is applied seas; neither will it be surprising, if the irregular na- to designate strata which seemed to have been formed ture of volcanic forces is considered, that the strata under nearly similar circumstances. A formation so elevated rarely are found in their originally level may consist of several systems-that is, strata having position, but in all degrees of inclination-sometimes nearly the same mineral and fossil character; and quite on edge, and even in certain rare instances folded there may be several grozups in a system, such as a backwards, so as to be upside down. sandstone or limestone group. All these groups consist of strata which, according to their thickness or external appearance, are designated beds, seams, layers, schists, or slates. Bearing these terms in mind, the Subjected from the earliest periods to these conflict- reader will be prepared to understand the following ing forces, the crust of the earth must have undergone tabular arrangement of stratified rocks as they occur frequent and extensive modifications - modifications in the British islands:-* not merely as regards distribution of land and water, * At this stage the student should direct his attention simply or of relative elevation and depression, but changes as to the names and order of the formations, systems, and groups — to the composition and arrangement of the rocky ma- returning to the details of the TABLE as a study after he has terial. The material of the first-formed rocks must perused the descriptive portion of the treatise. 20 GEOLOGY. SOIL-decompos ed vegetable and animal mat- It must not be supposed, however, that bandstheof strandstone.d ad ter, with earthy admixtures. rocks gin always occur in any posi tions, breakingof through earthem's crustin SUPER- Auim-depositsof slcandic massesgravel, and slay, in full and complete succession, ames overrunning them abovfter FICIAL. formed by NE the rdinary action of water. soD cLcuvoglmrae.the ma nnerposits of gravel anqud lava. Fromwith l that is meant is, that such would be their order ifs, boulders, formed by unusual operations of every group and formation were present. But whatwCOALMEASURES-alter. ever numbeds of groups mathey are in general better known byt, their mineveral comCRAO- Calcareous conglomerate of marine pe ut of their regula re fspaoiinta s shale, ironstone, a nd sandstone. position than by their order of ourre nce. Still, it may FeSoWs M OUNTAIN LIESTONEY s —thick-bedded gr clay- sla b e o never occurs abovid e coal, nor coal aboveat classeslk.,S y ~ ~ ~ ~ ~ ~~~ ste.ian limestones ind Fiesohorcales 9 F~~MARINE Bans-consisting of blue and i plastic Durham, magnesian limestone; bein Fife, th e - clays, thin beds of sand, lignEShite, &thick-. 4 CHALK-S bdesandstone, and clayre shl.basos o f all known rocks, and occurring along with the cOd Red halkes and mals. and lesswithout c ry stallin it would be st ructure thanless theo dig for chalknd System. green-sand. in Perthshire. It would not be absurd, however, to diSg GREEN-SAND -beds of green ferrginous for coal in Durham, because thco ndary and tertal underlies the sands, with chert nodules. magnesian limestone; or for old redsnsoei ie (WEALDEN esRoui-beds of clay, argillaceous Aeas htfrmto n tb sauandstoexpine Fife lsometimes quartzones, and sandc onglomeira te. Oli G OLITE-beds of olthite volcanimestone, calcarestill lesous occrystalline ander the compal strata of that county, in the reguyst miaeo. grits, sands, and clays, allof calompara tively recent orderiin, or suctill in procession. UPP SILURIAN rocks-ublgrayy and bluishar of formation. This division of the igneous rocks occur in noregular Silri a limestones, w ith coloured micaceou s shales. rocks subserves many useful purposes in geology, at SAa Ithe same time tOUS ALs-variegated shalet it is a distinction war ranted by the New Red shell limestone, with bands of sandstone, order or arrangement, heaving them out of their onSsdtse RaD SANDSTONE eRonu —fine-grained, some- ginal horizontal positions, breaking through them in flags. nature, aggregation, and aspect of their conglomerate.m e SIe ARD ARGILLACEOUS rocks —thick-bedded minerals. The ganitce, so named from thei r distinctly Gaacke sandstonesslaty sandstones and calclimestones. graulareous and crystalline texture, conglomprise granite, (COAL-MuaASURas-alternating beds of coal, they are in general better known by their niineral coinZ Sstoni-. FINshale, ironstone, and sandstone. position thand oby their vaorder of occurrence. Sti esll, it mayof Cray ca~oussN~TNEs l sats lCLAsY ish limestornels anad *shales. - iegranite. The trappean, and volcanic; granitic being the. System. > HORANBLENDE AND CmASTOLITE SLATES hills formed by these rocks, which include basalt, > t ~~~finely laminated. greenstone, clinkstone, trachyte, amygdlaloid, &c. The 1 ocabedded sanicdstones, and calcare those products dis YELLOW SchiANDSTONES, with beds of mottled rimary and transition strata; t-schist, trsappean, of a darker H C L RTSLTEs —reralneimsh-oouredn slartesck charged by recent or active volcanoes, such as lava, a: ~~~GN:EISS ROCKS —intermingled with irregular scotine, punrice, and tufa. As associated in the crust of nOld R bed shales andof quartz rock,and less crystalline listructure than, the unstratified granitified rocks would Sandste a -s. fse-grained, occurrin along with the secondary annexe d s etiary rocks;n: SyTestie. qartzose and conglomeratey. and the volcanic, stillon. Pcrystalline and compactimay. In the above section, the UNSTRATIFIED ROCKS appear in hills and irregular disrupting masses, from the older granite to the aRYO USTY-COLOUREDn SANDST~ONES~~~micactive volus, ano; while the STRATIFIED ccur in their regular order of succession. The Primatively recslope fromiin, or still in processfty granitie mountain, at a high angle, and in bluientsh or contorted strata;ion. This division oflie between the rangeous unof less elevtratified moun tSilurian lime Secondary occupy a still less elevated position, the Mountain imestone being raisefud lp on the hill-side, with the Coalogy, at Beds thrown into basin-shaped hollows, or broken up by faults, and the Magnesian Limestone and Chalk rising up into slight yseminpure shelly lime- the same Tertime thatr it is a distinction warranted by tthe sea-shore, or as diluvium, with boulders overlying the earlier formations. The reader will perceive how the Tertiary strata are said to be r emov e d from each other by a wide extent of country. ROCK FORMATIONS AND ORGANIC REMAINS. scribed. If the mass of the earth, ~herefore, were to AACEous rocks-thick-bedbe judged of from the thinc supo named from icial crust with whichtly Gramnoacke sandstones~slaty sandstones and limestones. granular and ciystalline texture, comprise gianite, ~riSystemY. FINE AND OARE-RAINE slaty rocks- syacquanite, serpentined, porphyiticand othere we not awvare of ities inconf Granite.Geologists iave been accus tomed o de- sistency wnit the ean ds thglobe, a a scerClySae CLAY-SLAT.E-finely laminated; dark, 1ier soclldfrmte s wep-ikeo iarraae a saidso are GlySae and purplish-coloured, ocle li h tplieo eicdsdso h System. HORNBLENDE AND CHIASTOLIrE SLATES- hills foimed by these iocks, which include basalt, {finely laminated. greenstone, clinkitone, trachyte, amygdaloid, &c. The Se-hi with mHOica, micaT-schist, talo- dschi esvolcanic, as the name implies, aie those pioducts disscribe this as t he lowest and olrys- charged by est or active volc anioes such appear to constitute lava, scertainy no other rock has ever been found bene ath it, the bulk of our planet-a cast nucle us on which af exept in peculiar circumstances afterwards to be eade-th the unstratified androcks restatified. Geologists are now disposed 21 System. and mica-schist. ~present something- like the annexed section: Tertiary. Secondary. Tsoausitiosn. I Pr-imary. In te abve ectin, he USTRAIFID ROKS ppea inhills and irregular disrupting masses, from the older granite to the actie vlcao; wiletheSTRTIFID ocurin teirreglarorder of succession. The Pr-imau-y slope from the side of a lofty graiti muntinata hgh nge, ndin bent or contorted strata; the Tu-ansition lie between the ranges of less elevated mountais; he ecnday ocup astil lsselevated position, the Mountain Limestone being raised up on the hill-side, with the Coal Bedsthrwn nto asi-shpedhollows, or broken up by faults, and the Magnesian Limestone and Chalk rising up into slight eminnce; th Tetiar inbasin-shaped strata; and the Ssspes~flcial.Acesmulatiesis occur either as sandy downs by the sea-shore, or a diuvim, wth oulersoverlying the earlier formations. The reader will perceive how the Tertiary strata are said to be abov th Col Masuesthogh heydo not overlie them; and how the Coal Beds are above the Transition Rocks, though remoed romeac othr b a ideextent of country. ROCKFORMTION ANDORGANIC REMAINS. scribed. if the mass of the earth, therefore, were to be judged of fr-om the thin superficial crust with which PRIMARY. ~~~~we are acquainted, and were we not aware of its incon0-ante.Geoogiss hve eenaccustomed to do- sistency with the mean density of the globe, as ascerscrie tis s th loestandoldest of all rocks; and tamned by astronomy, granite might appear to constitute cerainy o oherrok hs eerbeen found beiieath it, the bulk of our planet-a vast nucleus on which all excet i peulir cicumtanesafterwards to'be do- the stratified rocks rested. Geologists are now disposed, 21 CHAMBERS'S INFORMATION FOR THE PEOPLE. under a sense of their limited knowledge, to speak of the materials of the granite, we may suppose some granite, not as the lowest and oldest of all rocks, but chemical separation of those materials. as the lowest as yet discovered, and as one which, The most prevalent rock of the series is gneiss, a though in most of its forms old, is yet sometimes found compound, like granite, of quartz, felspar, mica, and of recent development. Granite, in fact, often appears hornblende, and so highly crystalline as to be someas an igneous rock, which has been thrown up in a times scarcely distinguishable from granite. A great state of fusion through superincumbent strata of all portion of the Highlands of Scotland is composed of kinds, penetrating into their chinks, and spreading strata of gneiss, of vast thickness. Mica-slate or micaover them on the surface. Even tertiary rocks are schiit, the next most prevalent rock of the series, is comfound broken up and covered by it-a proof that it posed of mica and quartz. It is the surface rock of has been ejected since the deposition of those rocks, many extensive tracts of country. Quartz rock, which which is one of the most recent events in geological we may suppose to have been formed by a chemical chronology. These are the peculiar circumstances in separation of that component of granite, is also a prewhich it may be said that other rocks sometimes lie valent rock. Humboldt takes notice of a mass of it in beneath granite. South America, more than 9500 feet in thickness. The Granite then may be described as generally forming round white pebbles, or' candy' stones, so often found a basis or bed for all the other rocks-as rising in some on sea-beaches and in the beds of rivers, are pieces of places from its unmeasured depths into chains of lofty quartz rock. Eurite, of which felspar is the main inhills-and as in other places penetrating in veins gredient, and horzblende rock, the chief element of through superincumbent rocks, and partially covering which is signified by its name, may also be accounted them. It composes a considerable portion of the moun- for by a chemical origin. tain-ranges of Cornwall, Cumberland, Wicklow in Ire- Clay-slate is the geological term for the well-known land, and the Scottish Highlands. The Alps, the Pyre- stone with which houses are roofed. It is, as its name nees, the Dofrafelds, the Abyssinian and other ranges in imports, composed mainly of clay-a substance too Africa, and the Andes in South America, are all more or liberally diffused amongst the ingredients of granite, to less composed of rocks partaking of a granitic character. admit of any wonder as to its being found in a nearly Three substances usually enter into the composition distinct state in this rock. Mica-slate and clay-slate of granite-namely, (I) quartz or silex, a whitish glassy are fissile in their structure-that is, capable of being substance, composed of oxygen in union with one of split into very thin plates: hence the utility of slate the metallic base, silicium; (2) felspar, also a crystal- as a material for covering houses. But a curious diverline substance, but usually opaque, and coloured pink sity exists in this respect between mica-slate and roofor yellow, composed of siliceous and clayey matter, with ing slate. In the former, the cleavage, or direction in a small mixture of lime and potash; (3) mica, a silvery which it splits, is in the same line as the stratification; glittering substance, which divides readily into thin but in roofing slate, the cleavage is always more or less leaves or flakes, and consisting principally of flint and transverse. What makes the latter circumstance the clay, with a little magnesia and oxide of iron. In some more remarkable —when strata of roofing slate are granites, instead of mica, we find hornblende, a dark found, as often happens, contorted or wavy, the direction crystalline substance, composed of alumina, silex or of the cleavage is in one straight line through them all, flint, and magnesia, with a considerable portion of the indicating that the influence which produced the cleavblack oxide of iron. Such granites are called Syezeite, age in that rock took effect after the whole had been from their abundance at Syene in Egypt. Other varte- laid down, and after, by some subsequent accident of ties are-Serpentine, in which there are dark spots like pressure, they had been forced into a wavy direction. those on the skin of the snake (hence the name), and Porphyry (from its reddish colour), of which the dis- a tinguishing peculiarity is its containing little angular pieces of felspar enclosed in the mass. Any igneous ///,' / rock containing such fragments, distinct from the com- // mon mass, is said to be porphyritic. Granite may then be regarded as a true igneous rock,* Section Exhibiting Lines of Cleavage in Clay-Slate. associated principally with the primary and transition Probably this phenomenon owes its origin to electric formations, but occasionally exhibiting itself in out- or magnetic agency. Clay-slates are found in great bursts and elevations among the strata of later eras. abundance in Cornwall, Wales, Cumberland, and the It presents numerous varieties; but these, either in the Scottish Highlands. A fine kind makes the slates used field or in cabinet specimens, are readily distinguish- at school, and from a kind still finer are cut the pens able from trappean and volcanic compounds. used for writing on school-slates. In the inferior stratified series there occur a few Inferior Stratified Series.-Above the granite, in its small beds of limestone, sometimes called Crystalline ordinary position, lies the inferior stratified series, con- or Saccharine Limestone, from its resemblance to refined sisting mainly of two kinds of rock-gneiss and mica- sugar, and sometimes Primitive Limestone, from the slate-with alternating strata of hornblende rock, period of its occurrence in the series. In Greece and quartz rock, eurite, talcose slates, chlorite slates, and Italy this rock has been subservient to the development argillaceous slates; of all of which it may be said that of national talents, the highest that have ever been they follow no very determinate order. The lowest of known of their class, for it is the marble from which these rocks are of the same materials as granite, in a the works of the Greek and Italian sculptors have been very slightly modified form, and they are nearly as formed. In the geological history of our globe, its first crystalline in their texture. Geologists also find in appearance in the ascending series of rocks is an event many places that the granite passes into them —a term of no small consequence; for limestone strata form a expressing a blending of the characters of rocks at the large proportion of the superior formations, and the line of their junction. These two facts have led to manner in which they have been formed has engaged the supposition, that the inferior stratified rocks were much attention. Limestone is the carbonate of lime; formed from the materials of the granite, disintegrated that is, a combination of the earth lime (itself a union by mechanical or chemical means, and washed into of the metal calcium and oxygen) with carbonic acid the beds of vast seas, where, on their deposition, they (this being, again, a union of oxygen with the elemenwere reached by the high temperature of the interior, tary substance carbon). Carbon is the largest element and thereby reconsolidated in a crystalline form. To in the composition of vegetable and animal substances, account for the rocks composed exclusively of one of and this its first appearance in the structure of rocks * To avoid all theory as to the origin of the Granitic Group, is of course a point of much interest, more espesome geologists employ the term hypogenme rocks (Gr. hypo, under, cially as it is generally concluded that many of the and ginomai): that is, nether or under-formed rocks. superior limestone strata have been entirely formed 22 GEOLOGY. of animal remains. We are thus tempted to surmise limestones are less crystalline than those of the early that the formation of the limestone beds of the inferior grauwackes; the arenaceous beds are also less siliceous, stratified series marks some early and obscure stage of and more closely resemble ordinary sandstones; while organic existence on the surface of our planet. No the abundance of organic remains justifies their arrangedistinct remains of plants or animals have indeed ment into a separate system. been found in the series; and it is customary to point The grauwacke forms the immediate surface in many to the next upper series, in which both do occur, as the large districts in Scotland, England, France, Germany, dawn of organic life. Yet many geologists are of opi- and North America, showing that at the time of its nion that the inferior stratified rocks might have con- formation' some general causes were in operation over tained such remains, though the heat under which the a large portion of the northern hemisphere, and that rocks seem to have been formed may have obliterated the result was the production of a thick and extensive every trace of such substances. The inferior stratified deposit, enveloping animals of similar organic structure series constitutes in most regions the great depository over a considerable surface.' The igneous rocks assoof the metals-gold, silver, tin, copper, &c.-which ciated with the transition series are chiefly granitic; occur in irregularly-intersecting veins, composed of ore- effusions of trap making their appearance only among stone differing in composition from that of the contain- the later strata. Perhaps the most extensive and ing strata. (For opinions as to the origin and character gigantic efforts of volcanic power were exhibited at the of metalliferous veins, we must refer to the article- close of this period; and there is abundant proof that METALS AND METALLURGY.') all the principal mountain-chains in the world were then upheaved. The Grampian and Welsh ranges, TRANsITION. the Pyrenees, Hartz mountains, Dofrafelds, Uralian, Grauwzacke and Silurian.-All the rocks hitherto de- Himaleh, Atlas range, Mountains of the Moon, and scribed are of crystalline texture, and, apparently, che- other African ridges, the Andes, and Alleghanies-all:nical phenomena have attended their formation. In seem to have received their present elevation at the the group we have now arrived at, traces of mechanical close of the transition period. origin and deposition become apparent; but still a few Fossils of the Grauwacke and Silurian.-The fossils strata resembling the preceding occur throughout the of the grauwacke and silurian (a few of which extend lower parts of this series, as if the circumstances under to the clayey and sandy slates immediately below) are which the earlier rocks were formed had not entirely of both plants and animals. Amongst the plants are ceased. Hence the term transition, as implying a pass- alga, or sea-weeds, showing that seas like the present ing from one state of things to another. now existed. Some land plants are also found, but of The rocks forming the lower part of this group, and the simpler structures-as filices, or ferns; equisetacece, which are sometimes separately classed as the Lowest a class of plants of the character of the mare's-tail of Fossiliferous Group, are an alternation of beds of chlo- our common marshes; and lycopodiacew, a class of the rite, talcose, and other slates, resembling those of the character of our club mosses. All of these land plants inferior stratified series, with beds of clayey and sandy are monocotyledons; that is, produced from seeds of a rock, of apparently mechanical origin, and thin beds of single lobe, and therefore endogenous-that is, growing limestone, in which a few fossils are found. It thus from within; timber plants being, on the contrary, the appears that the cessation of the chemical origin of produce of two-lobed seeds, and growing by exterior rocks, and the commencement of organic life, are layers. The Flora of this era thus appears of a very events nearly connected; and it has thence been sur- simple kind, indicating generally low-lying and marshy mised that the temperature of the earth's surface was habitats. now for the first time suitable to the production and The animals are also, in general, of a humble and maintenance of organic things. At the same time, the simple kind. There is abundance of those creatures alternation of the rocks teaches us the instructive fact, (polypi) resembling plants, which fix themselves on the that the change was not direct or uniform, but that bottom of the sea by stalks, and send forth branch-like for some time the two conditions of the surface super- arms for the purpose of catching prey, which they conseded each other. This is conformable with a general vey into an internal sac, and digest. At present, these observation, which has been made by Sir H. de la creatures abound in the bottoms of tropical seas, where Beche —namely, that however sudden changes may they live by devouring minute impurities which have have taken place in particular situations, a general escaped other marine tribes, and thus perform a service change of circumstances attending rock formations is analogous to that of earth-worms and other land tribes, usually seen to have been more or less gradual. The the business of which is to clear off all decaying animal few fbssils found in this part of the series-the Grau- and vegetable matter. But the class of animals found wacke proper-are, as far as ascertained, the same, or in greatest numbers in the grauwacke series of rocks nearly so, as those of the superincumbent Silurian. are shell-fish, possibly because the remains of these creaThe Silurian group-so called from its being very tures are peculiarly well calculated for preservation. clearly developed in that district of country between All over the earth, wherever grauwacke and silurian England and Wales which was inhabited by the ancient rocks are found, shell-fish are found imbedded in vast Silures —consists of arenaceous and slaty rocks, of quantities, proving that shell-fish were universal at the evidently mechanical origin, intermixed with nume- time when that class of rocks were formed. Among rous beds of limestone and calcareous shales. The the radiata or rayed animals, the crinoid or encrinife general composition of the series indicates its having family occur for the first time, these differing from been formed, like the grauwacke, of a fine detritus other corals in the self-dependent nature of their struc(matter washed from other rocks), and its having been ture, their fixed articulated stalk and floating stomach, deposited slowly; although, as in the case of the grau- furnished with movable rays for the seizure and retenwacke, the arenaceous beds occasionally pass into coarse tion of their food. As we ascend in the silurian group, conglomerates. Indeed, until a recent period, this the shell-fish become more numerous and distinct in system was considered as a portion of the grauwacke form; spirifers, terebratulce, and prod'uctce, are everygroup, and as marking its passage into the gray mica- where abundant; and chambered shells, like the existceous beds of the Old Red Sandstone. Merely looking ing nautilus, begin to people the waters. It must be at cabinet specimens, it would be impossible to distin- remarked, however, that the encrinites and chambered guish between many of the grauwacke and silurian shells of this early period are not so numerous, so rocks; but taking them in the mass, they are readily gigantic, or so elaborate in their forms as those of the distinguishable. In the first place, their sedimentary Secondary strata: it is in the mountain limestone group character is very marked; they present more rapid that the encrinites attain their meridian, and in the alternations from one kind of strata to another; they lias and oolite that the ammonites and nautili are most have undergone fewer changes by heat; and are gene- fully developed. rally looser and more earthy in their texture. The Of the crustacea of this era, the most interesting 23 CHAMBERS'S INFORMATION FOR THE PEOPLE. and abundant type is the trilobite (three-lobed), of shale. The sandstones pass, in fineness, from close. which several genera and many species have been de- grained fissile flags to thick beds of conglomerate, the scribed, and to which scarcely any existing creature latter being composed of pebbles from the size of a bears an ana- hazel-nut to that of a man's head. The whole system logy. The tri- is tinged with the peroxide of iron, the colours ranging l o b i t e (see from a dark rusty gray to brick-red, and from a mottled fig.) was a I purple and fawn shade to a cream-yellow. There are true crusta-'Z ~ A some calcareous beds in the system; but these are not cean, covered regularly developed, and are all siliceous and concrewith shelly tionary in their composition and texture. Taken in plates, ter- 1 the mass, the composition of this system is sufficiently minating va- indicated by the term old red sandstone-the epithet riously be-' old' being applied to distinguish it from another series hind in a / of red sandstones which occurs above the coal-measures, flexible ex- and is usually designated the new red sandstone. tremity, and The or ganic remains of the system, if not so numerous furnished as those of the grauwacke beneath, or the carboniferous with a head- measures above, are at least equally interesting, on piece comn- account of their peculiarities and adaptation to the po se d of s conditions under which they were destined to exist. larger plates, 4 The remains of plants are few and indistinct, but are and fitted apparently allied to those found in the true silurian with eyes of - rocks. Taken as a whole, the old red sandstone sysa very com- or thbernis Heinislxree c. So~uthern Hfemislphere. principle should be borne in mind; for if the elevation Arctic Zone, - 3,250,000 Antarctic Zone, of the land were less general, the waters would occupy Temperate Zone, 28,530,000 Temperate Zone, 3,830,000 larger spaces, and this more extended area of shallow Torrid Zone, - 11,620,000 Torrid Zone, = 12,210,000 water would act in various ways. It would render the climate more genial and uniform; and, extending a Total, - 43,400,000 Total, - - 16,040,000 greater surface to the evaporating power of the sun, The relative configuration of land and sea, we have 53 CHAMBERS'S INFORMATION FOR THE PEOPLE. said, is so extremely irregular, that no conception can and Flora-that serve to distinguish it as a whole from be formed of it unless from the study of a well-con- any of the other continents. The same may be said structed map; but whatever the character of this of South America, of North America, and of Oceania; configuration, it exercises a most important influence and in a less degree of Asia and Europe, which are on the physical operations of the globe, by determin- separated by no great natural boundary. Retaining, ing the direction of oceanic and tidal currents, and by therefore, these generally-acknowledged divisions, let modifying the direction and force of waves. Oceanic us glance at their respective positions and superficial currents influence the temnperature, and consequently characteristics as influencing the vitality of our planet. the life of the ocean; they carry along with them Europe-lying almost wholly within the northern every species of floating dibris-and this they deposit temperate zone, diversified by a happy blending of wherever the configuration of the land presents an ob- mountain and plain, marked by no geographical feature struction. Tides also exercise a powerful transporting on a scale so large as to give to its surface the character influence; they rise to greater or less heights, according of monotony, and surrounded and intersected by seas as they are obstructed by the outline of the land; and which greatly influence its climate-affords, in proporwhile they sweep headlands and promontories bare, tion to its area, a habitat to a more varied and highlythey lay down sand and gravel in sheltered bays. developed existence than any other quarter. Widely Waves also wear away the land, according as the line connected, however, with Asia on the east, as much of coast obstructs or favours the violence of their pro- of the two continents as lie within the same para.gress. Since, therefore, these oceanic agents are wear- lels present considerable similarity, at the same time ing away dry land in one quarter, and filling up shallow that every facility to the dispersion of species is bays and creeks in another; since rains and rivers are afforded by a land communication. Asia, situated wearing down inland regions, and carrying the mate- partly within the torrid, temperate, and frozen zones, rial to the sea; and since, moreover, earthquakes and and presenting an area almost five times that of volcanoes are here submerging land, and there ele- Europe, exhibits every species of geographical divervating the bottom of the ocean-the relative distri- sity-vast mountain-chains and elevated table-lands, bution of land and water must be continually fluctu- broad level steppes and sand deserts, luxuriant plains ating. However imperceptible this shifting may be- watered by the largest rivers, tracts doomed to everlittle affected as the existing continents may have been lasting snow or to scorching sterility, salubrious valwithin the historic period, or even within the era, of leys of incessant verdure, and noisome jungles of the man-still the change goes forward; and we are no grossest growth. With such a variety of character, it more entitled to regard the present distribution as a is impossible to treat of it as a whole, and consequently thing fixed and enduring, than an inhabitant of the geographers divide it into five well-marked regionsold red sandstone era (had any such existed) would namely, Central Asia, consisting of a series of ascendhave been to declare the then arrangement of land ing plateaux, diversified by mountain ridges of stuand sea as a thing immutable. pendous height, and intersected by narrow valleys; Nlrorthern, including the whole of the continent north of CONTINENTS AN-D ISLANDS. the Altai Mountains-a flattish region traversed by Thile qclarters or coztinents (though, strictly speaking, large rivers, bleak and barren, suffering under an there are only the two great continents already men- intense cold, thinly peopled, and almost physically tioned) into which it is usual to divide the dry land are incapable of improvement; Eacstern-upon the whole a Europe, Asia, and Africa in the Eastern Hemisphere; low-lying and somewhat arid region, though traversed North and South America in the Western; and Oceania by several of the largest rivers in the world, and occa(including Australia, Malaysia, and Polynesia), situated sionally diversified by spurs from the central table partly in both hemispheres. By referring to the map, heights; Southerss, including the two peninsularprojecit will be perceived that there are traces of land still tions of India within and without the Ganges —deunexplored both in the arctic and antarctic regions; cidedly the finest region of the continent, diversified but whether these may be islands or masses worthy to by minor hill-ranges and well-watered valleys, enjoybe ranked as new continents, we have yet few means of ing a high, though not an oppressive temperature, conjecture. At present, the comparative areas (in having only a rainy season for its winter, and, except square miles) of the established quarters-including during long drought, presenting in every district an their respective islands-are calculated as follows:- unfailing verdure; and lastly, Western Asia (from the Old 5World, or eastern continelnt,... 31,230,000.Indus westward and north to the Caspian), which, with Europe, or eastern continent,. 31,230,000 a few minor exceptions, may be said to consist of high Europe. 3,724,000 Asia,.16,152,000 sandy plains, studded with salt lakes, very inadeAfrica,.. 11,354,000 quately watered by rivers, and on the whole a hot and New World, or western continent,. 15,000,000 arid region. A continent marked by such a diversity South America,... 8,000,000 of surface and climate presents an appropriate field South America, 6,800,000 Maritime World, or Oceania, 4,632,000 for the exhibition of almost every form of vitality known in the other continents; and thus has belief The superficies of this vast expanse presents an amazing ever pointed to it as the cradle of organic existence. diversity of character; some portions being little ele- Africa, the next great division of the old world, is alvated above the sea-level, others rising into mountains most entirely insular, the isthmus connecting it with of more than five miles in height; some tracts swampy, Asia being only 72 miles across, of no great elevaothers arid; certain regions tame and fiat, others diver- tion above the sea-level, and even in part occupied by sified by the wildest irregularities; districts teeming, lakes and salt marshes. Respecting the physical apunder tropical influences, with life and growth, others pearance and construction of Africa our information is buried in the perpetual solitude of ice and snow. This extremely limited; all that is known with any degree diversity of character forms the especial object of our of certainty being some patches along the sea-board, arrangement and description. and a few tracks or lines across the Sahara, or Great Although the above division into' quarters' be con- Desert of the north. Little known, however, as it is, venient, and even justifiable enough, yet so much do its isolation, its intertropical position, and its general these sections run into each other, so largely do por- configuration, must stamp it with vital peculiarities; tions of one or more of them lie within the same paral- and yet its connection with Asia on the one hand, and lels, and so frequently are their other conditions akin, its proximity to Europe on the other (the Straits of that it is not very easy to draw a series of broad and Gibraltar being only about 8 miles in width), offer well- marked physical and vital distinctions between numerous facilities to the interchange of vegetable and them. And-yet there is something peculiar in the ex- animal species. Thus the southern and northern seaternal conditions of Africa-for example, something in board of the Mediterranean present many similar forms; its climate and superficies, its river-systemns, its Fauna the Flora and Fauna of Egypt and Nubia are identical 54 PHYSICAL GEOGRAPHY. in many instances with those of the adjoining tracts of garding Australia as a continent) are-Borneo, with Arabia; while the intertropical regions offer numerous an area of about 260,000 square miles; Madagascar, genera allied to those of Birmah and Hindoostan. 234,000; New Guinea, whose outline is yet imperfectly Turning now to the new world, we find too the two known; Sumatra, 128,000 square miles; Niphon, Americas so slenderly attached by the narrow rocky 109,000; Great Britain, 83,828; Nova Zembla, yet Isthmus of Panama, which at one part is little more imperfectly known; Newfoundland, 57,000; Cuba, than 18 miles across, that they may safely be regarded 43,400; and Iceland. 30,000 square miles. as separate and distinct continents. This separation Islands, we have said, are either connected with is rendered still more decided by the irregular charac- existing continents, are portions of former continents ter of the isthmus and the adjoining high table- now submerged, or are new and independent elevations. land of Mexico, which form an almost impassable Thus if an island is of the same geological formation barrier to the migration either of animal or of vegetable with the adjoining mainland, we must regard it either races. South America lies chiefly within the tropics, as a portion separated by depression, or as a belated a third part or less stretching southward into the portion only rising into dry land. In either case we temperate zone; its superficies is broadly marked by are bound to consider it in all its relations-vital as mountain and plain, exhibiting along the entire western well as physical-as belonging to the adjacent conticoast a flat arid region, from fifty to one hundred nent..Again, islands of totally different formation miles in breadth; then rising boldly up into the from that of the nearest continent may in most cases Andes, which stretch along its whole length, and be regarded either as relics of former lands, or as new present a rugged irregular region of variable breadth; lands rising into day; and we are not to be startled and ultimately falling away to the north and east in at the fact of their exhibiting (like Australia) races the llasos of the Orinoco, the plains of the Amazon, of plants and animals altogether peculiar. Lastly, and the pampas of La Plata. Nor are its physical with respect to far distant and solitary islets, whether features more broadly-marked than the plants and of volcanic origin or not, we must view them as indices animals by which it is peopled, these exhibiting typical of operations past or future, and as proofs of the fact, peculiarities only next in degree above those of the that the sea bottom presents the same irregularities as somewhat anomalous continent of Australia. Respect- the surface of the land-these islets towering above ing the entire configuration and extent of North the general configuration like the lofty peaks of existAmerica we have as yet no determinate knowledge. ing mountain ranges. If we adopt the opinion of Mr Simpson-who traversed Such is a brief glance at the partition of the dry the coast from Point Barrow to Point Turn-again-that land (so far as it is known) into continents and islands the waters of Melville Sound are connected with the -a partition which exercises an all-important influGulf of Bothnia, then is North America distinct from ence over organic existence, and which, after all, is the arctic regions of Cumberland Island, N. Georgia, dependent on very minute geological operations. A and Greenland, which will require to be erected into a general elevation of the solid crust in the eastern heminew geographical division. Following, however, the sphere, for example, would connect Britain with the usual course of including these regions, and leaving the continent of Europe, the Loffoden Islands with the G north-west passages as still problematical, the area Scandinavian peninsula, enlarge the connection beof the known continent may be stated at 8,200,000 tween Asia and Africa, elevate the Sunderbunds of the square miles-the great mass of which lies within the Ganges into a vast plain, the Laccadive and Maldive northern temperate zone. The general physical cha- reefs into extensive islands, and the bed of the Yellow racteristics of the continent are remarkable for the Sea into an alluvial plain. A depression to the same magnitude of the scale upon which they are presented amount, on the other hand, would sever Scandinavia -the plains, lakes, and rivers being superior to those from Europe, lay the Netherlands and part of Central of all other countries. Though lying chiefly within the Europe under water, sever Africa from Asia, convert a temperate zone, its southern and northern regions are large portion of Arabia, Egypt, and Northern Africa into respectively placed under tropical and arctic influences; an extension of the Mediterranean; il fact, totally and thus it presents in some measure the threefold overturn the existing relationship of the dry land in variety of Fauna and Flora which characterises the the old world. Similar phenomena would be presented greater continent of Asia. This greater diversity of under similar circumstances in the new world; and climate renders it less peculiar in its living forms than more strikingly still in connection with the islandthe sister continent, at the satne time that its proxi- groups of the Pacific. Equally important results demity to Asia-being separated by Behring's Straits, pend upon the relative positions of the continents and which are only 36 miles broad, and annually frozen islands. Had South America, unaltered in a single over —renders the immigration of old-world species square yard, lain parallel with, instead of crossing, the by no means improbable. equator, or had Africa been intersected by seas as The insular portions of the globe are not less worthy Europe is, it requires no stretch of imagination to conof notice than the continents themselves, though these ceive the radical difference which their Flora and Fauna in reality are but islands of greater extent, washed on would have presented. Whether the present arrangeall sides by the ocean. Meaning, however, by the ment of continent and island is that which admits of term island those smaller masses of land lying in the the greatest amount and variety of vital development, is midst of seas and lakes, we find them sometimes soli- what we have not yet sufficient data to determline; but tary, oftener collected into groups or archiFpelagos: in this we know, that the existing irregularity and varied some cases they are little more than low sand-banks, subjection to arctic, temperate, and tropical influences, ledges of rocks, or coral reefs; and in others'-rising is much more favourable to these results than any to a considerable elevation above the surface of the single influence, however gigantic its operation. Ny, water, and spreading to a considerable extent-they more, as regards man, and the highest aim of creation present in miniature all the features of the continents — the civilisation of man-the present arrangement is to which they belong. They are often the summits of of the first importance. The theatre of his operations submarine mountain chains, and, as such, are inti- all arctic, and he would never have risen above the mately connected with each other and with the neigh- condition of the Laplander or Esquimaux; all antarctic, bouring mainland. Many of them are evidently the and behold his condition in that of the miserable production of volcanic forces-the dawn of new conti- Fuegian; all tropical, and see him in a state of languid, nents emerging from the waters, as others are the gra- enervated, semi-civilisation; while balanced as condidually-submerging relics of former terrestrial regions. tions are, see his progress mainly in one broad zone, The most important island-groups are the British, where Chinese, Indian, Persian, Chaldean, Syrians, Japan, Philippine, and East Indian in the eastern Egyptian, Greek, Roman, Frank, and Anglo-Saxon have hemisphere; and the West Indian and Polynesian successively or simultaneously figured in the march of in the western. The largest individual islands (re- improvement. CHAMBERS'$ INFORMATION FOR THE PEOPLE. most of them are objectionable, as involving geological BMOUNrAINS AND TABLE-LANDS. theories: we shall adhere to that simpler arrangement As elevation above the waters of the ocean is the which takes into account merely their geographical origin of the dry land, so its most prominent features position and connection:-Those of Europe have been are those peculiar upheavals known by the name of classified into a number of systems, some of which are hills and mountains. They are the framework, so to continental, others insular. Laying aside minutie, speak, upon which the solid crust is built and com- the following seem to be distinct and natural:-1. The pacted; they are the immediate results of the elevat- Hesperian, embracing the mountain ridges of the Spaing forces mentioned under GEOLOGY; and according to nish peninsula-all of which maintain a wonderful their character, so is that of the regions to which they parallelism in position, as well as unity of character, belong, generally speaking, determined. They subserve and whose extreme culminating point is Maladetta in numerous and important purposes in nature. Rising the Pyrenees, 11,424 feet. 2. The Gallo-lFrancian sysinto regions of perpetual ice, they serve, in hot climates, tem, including all the hilly eminences in France which to temper the air with the breezes generated around lie to the north of the Garonne, west of the Rhone, and their heights; they are the reservoirs of rivers, supply- south of the Rhine. None of these are of great age, ing the shrinking streams, in the dry seasons of the or of great elevation, the highest beinc a peak of the lower countries, with copious torrents from their melt- Plomb de Cantal in Auvergne, 6113 feet. 3. The ing snows; they are, in most instances, the store- Alpuine system, embracing all those ridges and branches houses of the richest minerals; they increase and which radiate from the great Alpine range of Switzerdi-versify the surface of the earth; and, by presenting land, such as the Maritime, Cottian, Pennine, Rhetian, impassable barriers between opposite regions, they give Noric, and other Alps; the Apennines in Italy, and variety and richness to animal and vegetable life: we the Balkan or HRemus group in Turkey. This is the say impassable barriers, for the broadest seas are not great mountain development of Europe, under which, half so effective in obstructing the dispersion of vege- as one system, geographers used to comprehend the table and animal life, as lofty snow-clad mountains. whole of the southern groups and chains: the highest Seas have their tides, and currents, and drifting winds, or culminating point is Mont Blanc in Switzerland, and waves-even the polar seas have their firm ice- 15,732 feet. 4. The Hercynio-eCaspathian system, infields and drifting ice-floes, on which plants and ani- eluding all the mountains and eminences comprehended mals may be borne; but the snow-clad summit is between the Rhine, Dnieper, and Danube, the plains enduringly inapproachable by everything that partakes of Northern Germany and Western Poland. The of vitality. highest point in this system is Ruska-Poyana in the Isolated mountains of great height are of rare occur- Eastern Carpathians, 9912 feet. 5. The Scandinavian, rence, and when they do appear, are usually active a system of the highest antiquity, embracing the wellor recent volcanoes. Hills and mountains, whether defined chains of Norway, Sweden, and Lapland, the rising to the height of one thousand or twenty thou- extreme height of which does not exceed 8350 feet. sand feet, generally appear in chains or ranges, consist- 6. The Ural system or chain, which forms the boundarying either of one central chain, with branches running line between Europe and Asia, and rises in its highest off at right angles, or of several chains or ridges run- part to between 5000 and 6000 feet. Lastly, the Ling parallel to each other; and in both cases often Britannic system, consisting of a number of detached accompanied by subordinate chains of minor elevation. chains, as the Grampians, Cheviots, and Welsh mounSeveral chains constitute what is called a group; and tains, the highest point of which is Ben MacDhui in several groups a systenz. Geology -views these systems Aberdeenshire, 4390 feet. All of these systems, as axes as so many axes of elevation, necessary to the rise of of elevation, have long ago become fixed and permacertain formations from the bottom of the ocean; as- nent; none of them has for the last two thousand certains the direction and centre of the elevating force; years shown symptoms of volcanic activity: Hecla, explains the phenomenon of' crag and tail;' speculates Vesuvius, and Etna, the only active volcanoes in on the cause of the steep side being generally turned Europe, seem topoint to future upheavals. towards the older formations, while the gradual slope The mountains of Asia may be all traced from that looks towards the newer; and further determines the vast central plateau alreadyadverted to, which forms, as respective eras when they rose into existence, by ex- it were, the nucleus of the continent. Omitting ranges anmining the nature of the stratified deposits broken of minor altitude, we may enumerate —the Altai, through and carried up with the elevatory masses. forming the boundary between the Chinese empire Thus the Grampians, flanked and crested by no and Siberia, one of the bleakest ranges in the world, secondary rocks, long preceded the Pyrenees; the stretching unbroken for 500 miles ili length, and Pyrenees the Alps, which displaced the youngest reaching an extreme altitude of 11,500 feet; the secondary strata; and the Alps, again, had risen into lablonnoi and Stannavoi, which may be regarded as form while the site of _Etna was a shallow sea of prolongations of the Altai, stretching onwards to Behtertiay deposit. The relative ages of mountain ring's Straits, and attaining a height probably not chains appertains more especially to the province of exceeding 6600 feet; the IKhing-khan range, bounding the geologist; but with their epochs is connected their the Desert of Kobi, extending about 800 miles in physiognomy or contour, a subject eminently interest- length, but of unknown altitude; the Chalsg-pe-shan, ing to the geographer. So persistent is the contour of skirting the east coast of Mandshuria, and rising mountains, whether associated with the primitive, se- abruptly from the sea to a height of 5000 feet; the condary, or more recent formations, that the practised Pe-ling and YTn-ling ranges, on the west of China eye of the geologist can generally determine at a glance Proper, ramifying variously, probably attaining a culthe era of theirupheaval. The bold, but bald and mas- minating height of 11,000 or 11,500 feet, and branchsive heights of a granitic mountain, differ widely in as- ing southward through Birnlah and Annam in several pect from the abrupt and splintery crags and pinnacles parallel ridges which fall to 4000 and 3000 feet; the of a primitive; while the rounded, undulating, and great Hitmaleh mass, extending about 1300 miles in terraced outline of the secondary trap-hills distin- length, and from 200 to 250 across, rising from the guish them at once from the conical crateriform Indian side by stages of 4000, 8000, and 11,000 feet, heights of the tertiary era. Nor is it in appearance then swelling generally to 14,000, in about 200 points alone that these distinctions are interesting; the cold reaching a height of 18,000 feet, and in Dhwalagari barren subsoil of a granitic district, altogether indepen- and Chumulari to 28,000 feet-the greatest known altident of elevation, differs as widely in its vegetable ex- tuide of the terrestrial surface; the Ilindoo Koosh, with hibitions from those of a fertile and congenial trap as their southern ramifications, which may be regarded a cultured garden does from a moorland wild. as prolongations of the Himaleh; the Thian- chan in Respecting the classification of mountains various Central Tartary, rising to an absolute height of 11,000 plans have been adopted by continental writers; but or 12,000 feet, but only from 3000 to 4000 above the 56 PHYSICAL GEOGRAPHY. surrounding table-land; and lastly, the Taur'o-Cau- reach their extreme height at 6476 feet, and sink down casian system, diversifying the west of Asia with in their branches to 3000 and 2000 feet. numerous ridges and peaks, the highest of which is In Oceania we have several minor groups and ranges; Elburz, 17,796 feet. In connection with these systems but the principal elevations are in detached volcanic anld ridges are active volcanoes, as in Kamtchatka, heights, the index-fingers, as it were, to future mounJapan, the Thian-chan ranges, the plateau of Mongolia, tain systems. In Malaysia, the highest known point is &c.; and we are therefore not entitled to regard those Mount Ophir in Sumatra, 13,050 feet; Australia has so connected as having yet attained their ultimate no eminences of importance; but Polynesia has the stage of elevation. verdant and wooded heights of Tahiti, rising to 10,000 Of the mountain systems of Africa we know nothing feet; and the active craters of Owhyhee, respectively with certainty; a few detached facts are all that geo- 13,000, 14,000, and 16,000 feet above the sea-level. graphy can offer. The hills of Cape Colony rise from Such are the more prominent mountain systems Table Mount 3582 feet, to the Snieuveldt, 7400 feet, as known to geography. Those who regard them as and thence to the Nieuveldt, 10,000 feet, the interven- mere ridges, rising on one side, and descending as ing spaces being shrubby hloofs or valleys, and broad abruptly on the other, and at most intersected by a few grassy terraces or karoos. Of the Lupata chain, or narrow passes, gorges, and ravines, form a very erroneous' Backbone of the World,' as it is called by the older conception of the physical contour of the globe; for, so geographers, nothing is known, save that it skirts, far from this being the case, most of these systems are almost unbroken, the entire eastern sea-board of the but the escarpments or ramparts of elevated expanses continent; and information is equally deficient respect- known as plateaux or table-lands, which form in some ing the clustering ridges of Abyssinia and Nubia, and instances the nucleus of continents, and the source the more linear ranges of Kong, Donga, and Cameroon. frorm which the rivers of such continents flow. Thus, on The last, it has been ascertained, rise to an elevation examining the map of Asia, it will be seen that all the of more than 13,000 feet; but whether this be the rivers flow-north, east, south, and west-from the maximum, or whether the whole may not belong to central region, which in reality forms a succession of one system, further exploration can alone determine. remarkable plateaux. These plateaux may be termed On the north, between the Sahara and the Mediter- the Persian, which ranges from 3000 to 6000 feet above ranean, the Atlas system is well-defined, and here an the sea; the MIongolian, at an elevation of from 8000 elevation of 11,400 feet has been ascertained; but to 12,000 feet; and that of Thibet, which is still more some peaks in the chain rise much higher, and, accord- elevated. There are some masses of this kind in ing to recent accounts, seem to be permanently covered Europe, but of comparatively small extent-as the cenwith snow-a fact which would seems to indicate an tral part of Spain, which is about 2200 feet in height; altitude of more than 15,000 feet. and the Swiss table-land, between 3000 and 4000 feet. The mountains which traverse South America may We know too little of Africa to speak of its interior; be ranked under two systems-the Cordilleras or Andes but a large part of New Granada and Ecuador in South proper, and the Brazilian Andes. The former, in se- America is situated at an elevation of from 5000 to veral parallel chains, extend from the Straits of Ma- 9000 feet, and contains populous cities, such as Quito, gellan to the Caribbean Sea, in many places spreading Bogota, &c. One of the lmost noted of these tableout over a breadth of several hundred miles, embracing lands is that of Mexico, not less remarkable for its lofty table-lands, containing mountain lakes, and every- elevation than for its extent.' On the eastern and where intersected by steep narrow ravines, passes, and western coasts are low countries, from which, on jourlofty waterfalls. At Popayan, the main chain divides neying into the interior, you immediately begin to asinto three ridges, one of which, shooting off to the cend, climbing, to all appearance, a succession of lofty north-west, passes into the Isthmus of Panama; a se- mountains. But the whole interior is, in fact, thus cond separates the valleys of the Cauca and Magdalena; raised into the air from 4000 to 8000 feet. The conforand a third, passing off to the north-east, separates the mation of the country has most important moral and valley of the Magdalena from the plains of the Meta. physical results; for while it gives to the table-land, on The highest summits of the system are between 15 and which the population is chiefly concentrated, a mild, 17 degrees south, where Sorata reaches the elevation of temperate, and healthy climate, unknown in the burn25,350, and Illimani that of 24,200 feet; throughout ing and deadly tracts of low country into which a day's Chili and Peru they range from 15,000 to 23,000 feet; journey may carry the traveller, it also shuts out the in Columbia, from 14,000 to 18,000 feet; and in Pata- former from an easy communication with the sea, and gonia, from 4000 to 8500. Altogether the Andes pre- thus deprives it of a ready access to a market for its sent a most magnificent spectacle to the voyager on agricultural productions.' As with the hexican, so the Pacific; the snow, which permanently covers their with all other table-lands, according to their latitude lofty summits, even under the burning sun of the and elevation. Under the tropics they become theatres equator, contrasting beautifully with the deep blue of for the exhibition of temperate or even of arctic species; the sky beyond; while occasionally another contrast is while under a temperate zone they are inhabited solely exhibited in vast volumes of smoke and fire, emitted by boreal forms. from some of the numerous volcanoes which stud the entire range. The Brazilian Andes occupy a great EARTHQUAKES AND VOLCANOES. breadth of country, but seldom exceed an elevation of These are rather agents than effects-rather the 6000 feet. cause of geographical diversity than geographical feaThe mountains of North America are scarcely in tures themselves; and in this respect belong more proproportion to the other physical features of that con- perly to the province of geology: still, as by far the tinent, either in point of continuity or of altitude. greater portion of superficial irregularity is the direct Regarding the Cordilleras of Panama and Mexico, the result of their operations, and as it is often impossible Californian or Maritime range, and the Rocky Moun- to separate cause from effect, it will be necessary here tains, as portions of the great system of the Andes to give them some farther consideration. An earthproper, we have in Guatemala a culminating point of quake may produce a momentary undulation of the 14,900 feet; in the Mexican volcano of Popocatepetl, ground, followed by no perceptible result; it may simply of 17,735; in the table-land of Mexico, a general height elevate one region or depress another; it may be atfrom 4000 to 8000 feet; and in the Californian range, tended by a vast destruction of animal life, and the an average altitude of 8000 or 10,000 feet, which sud- submergence of forests; it may alter the course of rivers, denly rises to 12,630 in Mount St Elias. The Rocky and produce new shores and beaches; it may create M1ountains-the greatest and most continuous of the vast tidal waves, which give rise to accumulations of North American chains-rise from 8000 to 10,000, oc- ddbris; open new springs and fissures, from which issue casionally to 12,000, and only between 52 and 53 de- various products differing from those hitherto known grees north, to 16,000 feet; while the Alleghazies in the district. Innumerable instances of such changes 57 CHAMBERS$S INFORMATIONN FOR THE PEOPLE. could be cited; a few, however, will suffice to convince ness, that it contains vast caverns, and is extensively the reader of the importance of this class of physical fissured-primarily by unequal contraction from coolagencies:-By the great Chili earthquake of 1822, an ing, and subsequently by subterranean agitations. immense tract of ground-not less than 100,000 square Through these fissures water finds its way to the heated miles-was permanently elevated from two to six feet mass within; this generates steam and other gases, and above its former level; and part of the bottom of the these exploding, and struggling to expand, produce sea remained bare and dry at high water, with beds of earthquakes and agitations, which are rendered more oysters, mussels, and other shells adhering to the rocks alarming by the cavernous and broken structure of the on which they grew, the fish being all dead, and ex- crust, and the yielding material upon which it rests. halihg most offensive effluvia. By an earthquake in Occasionally these vapours make their way through 1819, a tract-the Ullah Bund-in the delta of the fissures and other apertures as gaseous exhalations, or Indus, extending nearly 50 miles in length, and 16 in as hot springs and jets of steam and water, like the breadth, was upheaved ten feet; while adjoining dis- geysers of Iceland. On the other hand, when the extricts were depressed, and the features of the delta com- pansive forces within become so powerful as to break pletely altered. The earthquakes of Calabria, which through the earth's crust, discharges of lava, red-hot lasted for nearly four years-from 1783 to the end of stones, ashes, dust, steam, and other vapours follow; 1786-produced numerous fissures, landslips, new lakes, and repeated discharges of solid material gradually ravines, currents of mud, falls of the sea-cliffs, and form volcanic cones and mountain ranges. It does not other changes, which, taken in conjunction, afford one follow, however, that volcanic discharges must always of the finest examples of the complicated alterations take place at the point where the greatest internal which may result from a single series of subterranean pressure is exerted, for volumes of expansive vapour movements, even though of no great violence. In 1743, press equally upon the crust and upon the fluid mass the town of Guatemala in Mexico, with all its riches, within, so that the latter will be propelled towards and eight thousand families, was swallowed up, and whatever craters or fissures do already exist. This theory every vestige of its former existence obliterated; the of central heat is further supported by the occurrence spot being now indicated by a frightful desert, four of igneous phenomena in all regions of the globe, and leagues distant from the present town. In 1692, a by the fact, that most volcanic centres are in intimate similar calamity overtook the town of Port-Royal in connection with each other-a commotion in one disJamaica, when the whole island was frightfully con- trict being usually accompanied by similar disturbvulsed, and about 1000 acres in the vicinity of the town ances in another. The only other hypothesis which submerged to the depth of fifty feet. has met with countenance from geologists is that Volcanic forces act in a similar manner, in as far as which supposes the internal heat to be the result of they elevate, depress, and break asunder portions of the chemical action among the materials composing the earth's crust; indeed earthquakes and volcanic throes, earth's crust. Some of the metallic bases of the alkaconsidered as subterranean movements merely, produce lies and earths, as potassium, the moment they touch precisely the same results. But volcanoes, properly so water, explode, burn, melt, and become converted into called, act in another and equally important manner red-hot matter, not unlike certain lavas. This fact in producing geographical changes. They elevate the has given rise to the supposition that such bases may crust into long continuous ridges or mountain chains, exist within the globe, where, water finding its way to form isolated cones, and discharge accumulations of them, they explode and burn, fusing the rocks among lava, scorin, ashes, loose stones; and other igneous which they occur, creating various gases, and producing debris. Geologists and geographers often amuse themn- caverns, fissures, eruptions, and other phenomena atselves by enumerating volcanic vents to the amount of tendant upon earthquakes and volcanoes. As yet, our 300 or thereby; but this is of little moment compared knowledge of the earth's crust at great depths is exwith the determination of the centres of elevation to cessively limited; we know little of the chemical and which they belong. In Europe there appears to be magnetic operations which may be going forward among three centres of volcanic action-namely, that of the its strata; and we are equally ignorant of the transpoLevant, to which AEtna and Vesuvius belong; that of sitions which may take place among its metallic and Iceland, represented by Hecla and the craters of Jan earthy materials; but judging from what we do know, Meyen; and that of the Azores in the Atlantic. In this theory, however ingenious, seems by no means Asia there is abundant evidence of volcanic action on adequate to the results produced. It is true that there the borders of the Mediterranean, the Black Sea, the occurs nothing among the products of volcanoes at Caspian, and the Persian Gulf; while along the eastern variance with its assumptions; but the magnitude, the borders of that continent there is a range not less than universality, and the perpetuity of volcanic action, point 5000 miles in length and 250 in breadth, including to a more stable and uniform source-that source being Sumatra, Java, the Eastern Moluccas, and the Philip- the internal heat or residue of that igneous condition pine Islands; the same range bearing farther north- in which our planets originally appeared. ward, though less distinctly, for several thousand miles, and terminating in the volcanic cones of the Aleutian PLAINS-VALLEYS-AND OTHER DEPRESSIONS. isles. The whole extent of the two Americas is also The plains, or level portions of the earth's surface, traversed by a volcanic range, manifesting itself by form a feature in its physical aspect equally important eruptions along the whole line, from the Rocky Moun- with that presented by its mountain systems. The tains, through Mexico and the Andes, onward to Pata- name is given to extensive tracts whose surface in the gonia and Terra del Fuego. The islands of the Pacific main is level, or but slightly broken by elevations and further attest the presence of similar forces, as in the depressions. They are found at all elevations above New Zealand, Sandwich, and other groups; as do those the sea, and of every degree of fertility; from the -namely, the Canaries, Cape de Verd, Ascension, St exuberant tropical delta just emerging from the water, Helena, Madagascar, Bourbon, &c.-which surround to the irreclaimable sterility of the desert of everthe continent of Africa. In these centres of igneous shifting sand. In the economy of nature they constiaction many of the volcanoes are extintct, others are tute the chief theatres of vitality: there plants, from merely dorsnant, while many are incessantly active. the lowliest herbage to the most gigantic timber-trees, The carese of volcanoes, earthlquakes, and other sub- flourish in greatest perfection and abundance; there terranean movements, has been the subject of several animals, governed by food instincts, congregate most theories, but is yet by no means very satisfactorily densely; and there man, led by similar instincts, and determined. The most prevalent opinion is that which by the higher purposes of social life, has chiefly planted connects them with one great source of central heat- his habitation. the residue of that incandescent state in which our The noblest of these expanses are the river plains of globe originally appeared. By this hypothesis it is the new world, drained by such waters as the Missisassumed that the crust of the earth is of various thick- sippi, the Amazon, and La Plata. In North America, 58 PHYSICAL GEOGRAPHY. the basin or drainage of the Mississippi is estimated extinct, whose remains had either been drifted thither, at 1,300,000 square miles, and that of the St Lawrence or who, while alive, had fled there for a last shelter at 600,000; while northward of the 50th parallel ex- during some of nature's extraordinary convulsions. tends an inhospitable flat of perhaps still greater dimensions. Much of the former expanse is rolling or THE OCEAN. undulating in its surface, well watered by minor rivers, The ocean, though in fact a single mass of fluid exhibiting broad grassy prairies and extensive pine resting in the hollows of the solid crust, surrounding forests; the second is more irregular in surface, largely the dry land on all sides, and indenting it with numeoccupied by lakes, and cumbered with forest growth; rous bays and gulfs, is generally divided by geographers while the last is a bleak and desolate waste, overspread into the following great basins:-The Pacific Ocean, with innumerable lakes, and resembling Siberia in the 11,000 miles in length from east to west, and 8000 ill physical character of its surface and the rigour of its breadth, covering an area of 50,000,000 square miles; climate. In South America we have first the low belt the Atlaeltic, 8600 miles in length from north to south, of country skirting the shores of the Pacific, from 50 and from 1800 to 5400 in breadth, covering about to 100 miles in width, and about 4000 in length, fertile 25,000,000 square miles; the gIsclind Ocean, lying beat its extremities, but in the middle sandy and arid; tween 40 degrees south and 25 degrees north latitude, next the basin of the Orinoco, consisting of extensive is about 4500 imiles in length anct as mlany in breadth, plains called llanos, either destitute of wood, or merely covering a surface of 17,000,000 square miles; the Andotted with trees, but covered during part of the year tarctic Ocean, lying round the South Pole, and joining with tall herbage; then the basin of the Amazon, a vast the Indian Ocean in the latitude of 40 degrees south, plain, embracing a surface of nearly 2,000,000 square and the Pacific in 50 degrees, embraces an area (inmiles, possessing a rich soil and humid climate, and clusive of whatever land it may contain) of 30,000,000 almost entirely covered with dense forests and impene- square miles; and the Arctic Ocean, which surrounds trable jungle marshes by the river sides; and lastly, the North Pole, and lies to the north of Asia and the great valley of the Plata, occupied chiefly by open America, having a circuit of about 8400 miles. Beplains called pampas, in some parts saline and barren, sides these great basins, there are other seas of considerbut in general clothed with weeds, thistles, and tall able extent, as the Mediterranean, covering asn area of grasses. Next in order of importance is that section 1,000,000 square miles; the German Ocean, 153,700; of Europe extending from the German Sea, through the Baltic, 134,900;. the Black Sea, with its suborcliPrussia, Poland, and Russia, towards the Ural Moun- nate gulfs and branches, 181,000; but these and other tains, presenting indifferently tracts of heath, sand, minor sections will be more app-opriately described and open pasture, and regarded by geographers as one when we come to treat of the respective countries vast plain. So flat is the general profile of this region, (Volume II.) with which they are politically as well as that it has been remarked' it is possible to draw a physically associated. line from London to Moscow, which would not per- Respecting the deptht of the ocean we have no very ceptibly vary from a dead level! Passing the Ural definite knowledge; but this we may assume, a priori, ridge, a plain of still greater dimensions stretches on- that it possesses great irregularity of depth and shallowward through Siberia, towards the shores of the Pacific. ness, just as the terrestrial surface presents diversity of This region is of no great elevation, and though diver- hill and plain, and that, as the loftiest mountains rise sified by occasional heights, consists chiefly of gravelly about five miles in height, so the extreme depth of the steppes, covered with coarse herbage, lakes, and mo- ocean may not greatly exceed that measure. In the rasses. In Africa, the northern and central portion, North Atlantic, Lord Mulgrave did not touch the so far as explored, appears to be a vast expanse of ground with a sounding line of 4680 feet, and. Mr Sahara, or sandy desert, broken at scanty intervals by Scoresby was equally unsuccessful with one of 7200 oases of life and verdure. feet; while in latitude 15~ 3' S., and longitude 23' 14' Besides these wide expanses, which may be said to W., Sir James Ross tried, but did not obtain soundcounterbalance the mountain systems, there are plains ings, with a line of 27,600 feet! Having nearly ascerof minor extent, which often stamp the countries to tained its superficies, and assuming average depths, which they belong with a peculiar character. These many have amused themselves with calculating the are the verdant prairies of North America, already probable quantity of water in the ocean; but all such noticed, the pamnpas and llanos of South America, the calculations, in the absence of anything like data, are steppes of Asia and Northern Europe, the tunldras or worse than worthless. This only we know, that the bog-marshes of Siberia, the grassy karoos of Southern quantity, whatever it may be, remains, by the unalterAfrica, the tangled jugles of India, the alluvial straths able laws of evaporation and condensation, always at or dales of our island, and the low muddy, but gra- a fixed point, there being neither increase nor decrease. dually-increasing deltas of such rivers as the Ganges, It has been remarked by La Place, a French astronoNile, Niger, and Mississippi. To lesser fiats and de- mer, that if the existing waters of the ocean were inpressions-as valleys, glens, ravines, &c.-which give creased only one-fourth, the earth would be drowned, character to the landscape of minor districts, our space with the exception of some of the highest mountains; -will not permit us to refer. Physically, they produce and that if, on the other hand, the waters were dimiresults akin to those of larger depressions; and whether nished in the same proportion, the largest rivers would they be the subsidences occasioned by earthquakes, the dwindle to the capacity of brooks, and some of the sites of silted-up lakes, valleys of erosion, or ravines of principal arms of the sea would entirely disappear, volcanic rupture, it is the province of geology, not of while at the samie time the earth would be deprived of geography, to determine. its due proportion of humidity, and the face of nature Under this head it is usual to describe fisszres, be dried up and rendered desolate. The pressure of caverns, and other ssubter'raneazee openings; but as these the ocean (which depends on its depth) exerts an imare interesting more on account of their curious struc- portant influence, inasmuch as it renders it impossible tures, than from any effect they produce on the aspect for plants or animals to exist beyond a comparatively or conditions of the globe, we shall leave them to be limited distance from the shore or depth from the surnoticed, as occasion may offer, under the respective face. Teeming as the ocean is with life, its greater countries in which they occur. This only we may ob- depths seem to be as void and desolate as the peaks of serve, that they owe their formation either to earth- the snow-clad mountains. quakes and volcanic convulsions, to the erosion of sub- Water being a slow conductor of heat, the tenperaterranean springs and streams, or to the action of waves ture of the ocean is less affected by seasonal influences, and tides, when the cliffs in which they are situated and much more uniform, than that of the atmosphere, formed the shores of the ocean. They become indices, while the action of currents and counter-currents tends in this way, to bygone operations; and are not unfre- to equalise its heat in all latitudes. Within the troquently the catacombs, as it were, of animals long ago pics the surface temperature ranges between 77 and 84 59 CHAMBERS'S INFORMATION FOR THE PEOPLE. degrees Fahrenheit; but at the depth of 300 feet or fleeted or transmitted to the eye, a certain portion of thereby the solar influence is unfelt. In the torrid it, consisting of more or less of its colours, is lost in zone the temperature diminishes with the depth; in the body. The remainder, being reflected, strikes our the polar seas it increases with the depth; and about vision, and whatever colour that may be, the object the latitude of 70 degrees it is nearly constant at all seems of that colour. Now it chances that the portion depths. Taking the month of March as one of those of light most apt to be reflected from masses of transduring which the heat of the sun must be equally de- parent fluid is the blue; hence it is, or supposed to termined in both directions by latitude, we find that be, that the air and sea both appear of this colour. in that month the sea has been found, at 11~ 32' S., of While there can be no doubt that the ocean is gene80'6 Fahrenheit; at 31~ 34' S., of 75-7; at 40' 36' S., rally of a blue colour, it is equally certain that there of 59'9; though in some instances it has been found are many portions of sea in which a different hue apseveral degrees more or less at the same season, and pears. The causes of these exceptions fromn the rule under nearly the same latitude. A small difference seem to be of various kinds. Frequently the ordinary is discovered between the observations on temperature colour of the sea is affected by the admixture of foreign in the two hemispheres. For the first 25 degrees to- substances, these being sometimes of a living and orwards the south the decrease of heat is slower, and ganic nature, and sometimes the reverse. The most after that more rapid, than towards the north. It simple example of the latter class of cases is the conlmust be evident to every one who considers the great mon flooding of any stream, when quantities of mud mass of waters composing the ocean; and the inter- and earthy particles are introduced into the river, and change of position which must always be taking place, emptied into the sea. What is thus strikingly seen on to a greater or less extent, between the warmer and every coast, on a small scale, will readily be conceived colder portions, that this comparative equability of to be of infinitely wider extent in the mighty rivers of temperature is unavoidable, even if there were no other the principal continents of the globe. Some seas are causes to account for it. The uses of that equability coloured yellow from a similar cause. Vegetable matter are still more obvious: by it the natural result of high is known to have a colouring effect; but more usually latitude is more or less corrected. A milder air breath- the peculiar tint, whether red, green, &c. of the sea, ing from the sea softens the climate all over the ad- results from the presence of infusorial animalcules. jacent land, and produces a congeniality which is of Another class of cases in which the ocean appears to be the greatest service. On the other hand, in those tor- tinged with a peculiar colour, is referable to the reflecrid regions where both animated and vegetable nature tion of rays of light from the bed or bottom; and hence, is apt to sink beneath the vertical rays of the sun, in shallow and clear seas, the colour of the ground is a the cooling breath of the ocean comes, generally at main cause of any particular tint which the water may regular intervals, communicating freshness and vigour there assume. to all around. The phosphorescence of the ocean, described in such The saline property of the ocean, to which we have glowing terms by almost every voyager in tropical seas, already adverted in general terms (p. 51), has never is now satisfactorily ascertained to arise sometimes from been scientifically accounted for; it baffles all human the presence of zoophytes and infusorial animalcules, investigation. Some have alleged that it is caused by and at others from the decomposition of vegetable fossil or rock-salt at the bottom; others that the saline and animal matter. Similar phenomena, arising from constituents are carried down by springs and rivers from similar causes, exist on land-the glow-worm, firefly, the land; but neither hypothesis will account for all certain fungi, putrid fish, &c.-and their appearance in the phenomena; while, if the latter were true, the ocean the one element need not excite greater surprise than would be gradually becoming salter in consequence their exhibition in the other. of incessant contributions. The most reasonable conclusion is, that the sea is a homogeneous salt body; TIDES-CURRENTS —WAVES. that its waters were created, and have continued, and The waters of the ocean are subject to various mnoever will continue, in this saline condition, in the same tions and fluctuations, such as tides, currents, whirlmanner that the atmosphere has been created and pools, waves. That regular ebb and flow known by the exists as a compound body. The inquiry, therefore, name of tides, and which confers on the ocean one of why the sea is salt, is just as needless as why the at- its most interesting features, is caused by the attracmoosphere is composed of two or three gases. The'two tion of the sun and moon. By the universal law of questions are equally shrouded in mystery. All that gravitation, all masses of matter have a tendency to be we know for certain is, that the ocean is not of uniform attracted or drawn towards each other. The moon, saltness; that the Southern Ocean, for example, con- therefore, as a mass of matter, in passing round the tains more than the Northern; that inland seas are earth has a tendency to draw the earth after it, or out generally more saline than the open ocean; and that the of its natural relative position; and it really does so to surface water is somewhat fresher than that obtained a small extent. As it passes round, it draws up the from considerable depths. The gravity conferred on waters in a protuberance, or, in common language, the water of the ocean by its saline property is 1'027, reckoning distilled water at 60 degrees Fahrenheit equal to 1; and to this density it owes its supe-/ rior buoyant powers. Again, fresh water, under ordi- i r nary circumstances, freezes at 32 degrees Fahrenheit, 1t_'_ whereas the water of the ocean requires a degree of cold equal to 28 degrees; and the ice then formed is, \ X irregular, porous, and charged with vesicles full of a dense briny liquid. The colour and phosphorescence of the ocean are the draws a huge wave after it. But it also draws the land next sensible properties requiring attention. When beneath the protuberance, and so causes the opposite examined in small quantities, sea water is colourless; side of the globe to be drawn away from the ocean, but when viewed in the mass in the wide ocean, it ap- leaving the waters there to form a similar protuberance pears to be of an azure or blue tint. The cause of this or high wave. In the one case, the water is drawn generally blue colour has not been as yet clearly ex- directly up or towards the moon (M); in the other, the plained; but it seems to be in some degree accounted water is in some shape left behind by the land being for by reference to certain principles connected with pulled away from it. In both a similar effect is prothe science of optics. Probably most are aware that duced: two tides (t t') are caused at opposite extremilight consists of the set of colours which we see so beau- ties of the earth. Where the higher part of either of tifully displayed in the rainbow. Now it is a law of these great billows strikes our coasts, we have the phelight, that when it enters any body, and is either re- nomenon of high water; and when the lower touches 60 PHYSICAL GEOGRAPHY. us, it is low water. Each of the waves is brought over the rotatory motion of the earth. The globe in its any given place in the circumference of the earth in diurnal motion leaves, as it were, the fluid behind; twenty-four hours, so as to cause high water twice a and hence there is a perpetual flow of the sea from the day. The sun is also known to have a certain attrac- western coasts of Europe and Africa towards the eastern tive influence on the waters of the ocean; but from the land-board, as it is called, of America, and from the great distance of that luminary, the effect is compara- west of America to the eastern coast of Asia. This tively. small. But when this minor influence of the sun movement is chiefly confined to the tropics, unless coincides with that of the moon, or acts in the same line where the sea is turned aside by the land, and caused of attraction (M t), we perceive a marked increase in the to diverge towards the north or south. If we start in a tides; on such occasions we have what are called spring, survey of this motion from the western coast of Ameor large tides. When the solar and lunar attractions act rica, we find it producing a constant current across the in opposition, we have neap, or small tides. The spring vast expanse, of the Pacific, till it is turned off by Asia tides happen twice a month, when the moon is at full and Australia. A great division of its force is directed and change; and the neap when the moon is in the through the seas on both sides of the latter continent, middle of its orbit between those two points. A tide and so on through the Indian Ocean, and round the requires six hours to rise, which it does by small irn- Cape of Good Hope, till it reaches the free expanse of pulses or ripplings of the water on the shore, and six the Atlantic, across which it proceeds in the same hours to ebb or fall; but every successive high water is nlanner as across the Pacific. The current of the Atfrom twenty to twenty-seven minutes later than the lantic strikes the coast of Brazil, and breaks at Cape preceding, or, on an average, about fifty minutes for St Augustine into two divisions, one of which proceeds two tides, in consequence of the earth requiring that round Cape Horn into the Pacific, while the other adtime above the twenty-four hours to bring any given vances through the Caribbean Sea, and so on into the point again beneath the moon. The tides are thus Gulf of Mexico. This latter branch conspires, with the retarded by the same reason that the moon rises fifty vast issue of fresh waters which pours into the Gulf of minutes later every day. It is evident that the tides Mexico, to raise the level of that sea above that of the will be greatest at that point of the earth's surface neighbouring ocean; and causing the surplus to force which is nearest to the nmoon, or where the latter is its way out between Florida and Cuba, produces the vertical. She is so between the tropics; and accord- celebrated Gulf Stream, which is by far the most poweringly the tides are there greatest, and they diminish as ful marine current known. we approach either poles. It is further to be remarked, Besides the grand equatorial or tropical current, that the nmoon does not anywhere draw up the tides there is one of a less decided character from the poles immediately. Three hours elapse before the waters are to the equator. The sea under the tropics evaporates raised, in consequence of the law of inertia, or a dis- to a greater extent than elsewhere, by the influence of position which every body has to continue in the condi- a vertical sun. The vapours are apt to proceed towards tion of rest or motion in which it happens to be placed. the north and south, where they descend in rain. A This stubbornness to resist the rnsoon's influence is only surplus of water is thus produced in the high latitudes, overcome by a three hours' action upon the waters; and which naturally flows back towards the equator. Hence thus the tidal wave is always three hours behind the a constant but comparatively slight flow firom the north noon in its passage. Twice a year-namely, in March and south towards that warmer region of the earth. and September-the tides are higher than at other Under the influence of this stream, large masses of ice times, because then the attraction of the sun and moon are constantly becoming detached from the polar stores, is strongest. In some of the firths or arnms of the sea and drifted to the tropics. In some of the bays on the on the east coast of Scotland, it has been occasionally north side of Iceland this frigid substance comes in noticed that there have been four high waters in the vast quantities, insomuch as to choke them up to the twenty-four hours. These, however, are not simple depth of 500 feet. What is still more strange, these tides. The double risings are caused by the irregular masses of ice are sometimes mixed up with trees, some passage of the tidal wave from the Atlantic round the of which are known to be the produce of the torrid north and south points of the island of Great Britain. zone in Anmerica; this is accounted for by the action of When that portion of the wave which proceeds by the the northern division of the great current which parts south reaches the east coast sooner than that by the at Cape St Augustine. That northern division, after north, or vice versad, there will be two risings of the rushing into and out of the Gulf of Mexico, proceeds water instead of one. MIoreover, in consequence of all northward to Newfoundland, and thence at a high latithe great seas and oceans forming, as we have seen, tude returns athwart the Atlantic, finally sweeping only one sheet of water variously distributed, the ebb along the western coasts of Europe, and rejoining the and flow in each depend not on its own proper tide, current which gave it its first impulse. but are the result of the combination of that tide with The operation of the tides is less observable in the currents mingling with it from tides of other seas-a great currents we have alluded to than in those which result depending upon inequalities of sea-bottom, the prevail in the more secluded seas. The abstraction of configuration of its coasts, their inclination under water, water from a secluded sea by the recess of the tide, and the size and direction of the channel which connects it the rush inwards produced by its flow, are sufficienlt with other seas, and occasionally upon winds and cur- of themselves to cause very impetuous currents, more rents which are not tidal. So much do these circum- particularly in the narrow channels by which the instances affect the astronomical or primary tidal wave, land seas are connected with the ocean. We find it that while it rises in the expanse of the Pacific to one stated, in a pamphlet respecting the condition of the or two feet only, the derivecl wave often rises in con- Orkiley Islands, that the Pentland Firth, which sepafined or obstructed seas to elevations of thirty, forty, rates the continent of Great Britain from Orkney,' has or even seventy feet! This circumstance has given no fewer than four-and-twenty contrary currents of the rise to the determination of cotidal lines, or lines which tide at the flood of spring, besides numerous sets and mark the conItemporaneous position of the various eddies, which, under the local names of wells, swelches, points of the great wave which carries high water from and'oosts, boil more madly on the Orcadian shore than shore to shore. Inland expanses of water, like the ever did witch's caldron on the kindred coast of NorBaltic, Mediterranean, and Caspian Seas, and the way, if we may believe old tradition and Bishop Pon — lakes of North America, have no perceptible tides. toppidan. " The Boar of Papa," at the opposite extreme Besides being affected by the regular motion of the of Orkney, is another terrible tide; when he gets a tides, the ocean, in many parts of its extended bounds, vessel in his tusks, he shakes the masts out-an opeis influenced by currents, which act continually in par- ration which, in the country phrase, goes by the name ticular directions. Currents are the result of various of hackling.' The contrariety of influences which are causes-such as temperature, winds, peculiar construe- sometimes brought into play by polar and equatorial tion of coasts and inlets-but chiefly, as is believed, of currents, and those produced by the tides, occasion 61 CHAMBERS'S INFORMATION FOR THE PEOPLE. many phenomena extremely perplexing, and sometimes very dangerous, to the navigator. In the Cattegat, by LAIES AND RIVERS. which the Baltic is connected with the German Ocean, Lates are inland bodies of water not connected with one current always goes in by the side next Jutland, the ocean or any of its branches: they are generally while another issues forth by that nearest to Sweden. fresh, but are occasionally brackish, or even decidedly In like manner a current seems to proceed along the salt. They are classified according as they are fresh or eastern coast of Britain towards the south; while an- saline, and according to the manner in which they reother, flowing in an opposite direction, advances along ceive and discharge their waters-namely, those that the coast of Holland. What is still more curious, both receive and discharge running water; those that under-currents are sometimes found going in a contrary receive waters, but have no visible outlet, as the direction to those upon the surface. At the Straits of Caspian Sea; those which receive no running water Gibraltar, it has been ascertained there is always a (being fed by springs), but have an outlet; and such as surface-current setting in, as if to supply a want in the neither receive nor discharge running water. Lakes are Mediterranean, while at a certain depth there is an- distributed over the globe according to the inequalities other flowing outwards to the Atlantic. of surface; and all tend to annihilation, partly by siltTwo currents of equal force, but of different direc- ing up their basins, and partly by deepening their outtions, meeting in a narrow passage or gut, will cause a lets, thereby effecting an entire drainage of their waters. whirlpool, a phenomenon which has ignorantly been said By far the most gigantic are those of North Americato be produced by subterranean rivers, gulfs, chasms, such as Superior, Huron, Michigan, Erie, and Ontario, &c. but essentially is only an eddy, produced by the which respectively occupy 35,000, 20,000, 16,000, contact of two currents meeting on a centre. The 10,000, and 7200 square miles. Next in order are the whirlpool named the Euripides, near the coast of Greece, lakes of Asia, of which the largest are Aral and Baikal; alternately absorbs and rejects the water seven times in the surface of the former is estimated at 9930, and the twenty-four hours. Charybdis, in the Straits of Sicily, latter at 7540 square miles. Of the African lakes we absorbs and rejects the water thrice in twenty-four have no definite information; but Europe can boast of hours; and the Maelstroem, on the coast of Norway, a vast number, which, though generally small, give which is considerably the largest, absorbs, every six beauty and diversity to her landscapes. Those of Lahours, water, ships, whales-in short, everything that doga and Onega in Russia are the largest; the former approaches its malignant influence - and the next having a surface of 6330, and the latter of 3280 square six hours is employed in casting them up again. miles. A comparative estimate of the extent of these Eddies of this kind are occasionally augmented by vast sheets may be formed, when we mention that the the force of contending tides, or by the action of the area of Lake Geneva does not exceed 340 square miles. winds and waves. Lakes subserve important purposes in the economy Being an elastic and mobile fluid, water is readily of nature. They serve as reservoirs for the waters which acted upon by winds; and thus waves are produced, rivers would too speedily carry away from the land; varying in height and velocity according to the force they are the tanks, as it were, in which the impurities and continuity of the wind, extent of uninterrupted of streams subside; they refresh and enliven the landsurface, depth of the ocean, contending currents, and scape; and as they all tend to silt up their own sites, the like.' The common cause of waves,' says Dr Arsnott, these sites become in time tracts of fertile alluvium,' is the friction of the wind upon the surface of the and such has been the origin of some of our finest water. Little ridges or elevations first appear, which, plains. They are also the scenes of extensive and varied by continuance of the force, gradually increase until vital operations. The plants which spring from their they become the rolling mountains seen where the bottoms, or flourish by their margins, differ widely winds sweep over a great extent of water. In rounding from true terrestrial and maritime vegetation; while the Cape of Good Hope, waves are met with, or rather the animals which people their waters exhibit pecua swell, so vast, that a few ridges and a few depressions liarities not less distinct and characteristic. occupy the extent of a mile. But these are not so dan- Rivers, streams, sgprings-whether flowing with a vogerous to ships as a shorter sea, as it is termed, with lume several miles in breadth, or trickling in a tiny more perpendicular waves. The slope in the former is rill which a child's hand might obstruct-constitute so gentle, that the rising and falling are scarcely felt; a class of the most valuable agencies in the physical while the latter, by the sudden tossing of the vessel, is history of our globe. They are the irrigators of its often destructive. When a ship is sailing before the surface, adding alike to the beauty of the landscape wind, and riding over the lozng sswell, she advances as if and the fertility of the soil; they carry off impurities by leaps; for while each wave passes, she is first de- and every sort of waste d6bris, to be deposited in the scending headlong on its front, acquiring a velocity so ocean as the strata of future continents; and when of wild, that she can scarcely be steered; and soon after, sufficient volume, they form the most available of all when the wave has glided under her, she is climbing channels of communication with the interior of contion its back, and her motion is slackened almost to rest nents. Man has ever located himself by their banksbefore the following wave arrives. The velocity of using their waters for his domestic purposes, making waves has relation to their magnitude. The large their bosoms the highway of his commerce, and applywaves just spoken of proceed at the rate of from thirty ing the force of their currents to the abridgment of his to forty miles (an hour. It is a vulgar belief that the toil. They have ever been things of vitality and beauty water itself advances with the speed of the wave; but to the poet, silent monitors to the moralist, and agents in fact the.foirn only advances, while the substance, of comfort and civilisation to all mankind. The manexcept a little spray above, remains rising and falling ner of their origin is this: —The sun's heat, acting upon in the same place with the regularity of a pendulum. the ocean and other exposed surfaces of water, converts A wave of water, in this respect, is exactly imitated by that element into vapour; this vapour, invisible, and of the wave running along a stretched rope when one end less specific gravity than the atmosphere, ascends, and is shaken; or by the mimic waves of our theatres, forms clouds, mists, &c.; and when condensed by cold which are generally undulations of long pieces of car- or electric agency, as described under METEOROLOGY, pet, moved by attendants. But when a wave reaches falls by its specific gravity to the surface in the form of a shallow bank or beach, the water becomes really pro- dew, rain, hail, and snow. Falling on the surface ingressive; for then, as it cannot sink directly downwards, discriminately, these percolate the soil, find their way it falls over and forwards, seeking the level.' Sailors through the rents, fissures, and pores of the rocky strata, and others speak of waves running'mountains high;' and ultimately escape at some lower level in the form but it is questionable if, even in the dreaded Bay of of springs. Some of these springs are perennial, others Biscay, they ever attain an altitude of thirty feet, temporary or intermittent: some are limpid, and almeasuring from the trough of the sea to the crest of the most absolutely pure; others are impregnated with mesucceeding wave. tallic, earthy, and saline ingredients, according to the 62 PHYSICAL GEOGRAPHY. nature of the strata through which they have perco- luminary in winter. The decrease of heat as we recede lated: some are cold, others tepid; while many issue, from the equator is greater in the southern than in with bubbling and steam, near the ordinary boiling- the northern hemisphere. According to Humboldt, point of water. Springs, naturally tending to lower continents and large islands are warmer on their levels, unite and form streams; and these again falling western than on their eastern sides. The extremes of still lower, conjoin in valleys, and form rivers —creating temperature are'more felt in large inland tracts than in their course rapids, cataracts, and waterfalls, ravines in islands and situations near the coast. The sea aband dells, lakes, swamps, and marshes, alluvial plains, serbs and radiates heat more slowly than the land; and and low terminating deltas. The valley in which a thus, after the land has given out its last particle of river flows is usually termed its basin; and its drainage caloric, the ocean is radiating its tempering influences. is that portion of country drained by its streams or For these reasons, climatologists have found it necestributaries. It is the custom of geographers to compare sary to construct isothermal lines round the globe; that rivers by their lengths; but this does not always con- is, lines along which the annual mean temperature vey a correct idea either of their physical or economical is the same. Again, places which have the same importance; for some main trunks, of limited length, mean annual temperature vary considerably in their may drain a vast extent of country, and others of great mean summer and winter temperature; hence isocheilength may offer few or no facilities for commercial mnal lines, or lines of equal winter temperature; and transport. The following is an approximation to the isotheaal lines, or those which show equal sunmmer over proportional length, area of basin, and quantity of points upon different isothermal curves. Another set water discharged per annum by some of the principal of lines or curves, called isogeothermal, connect points rivers, reckoning the Thames as 1:- where the temperature of the soil is equal at or beneath the surface. RiverTs. Length. Basin. 1Discharge. Since the temperature of the atmosphere diminishes Thames, - - 1... 1... 1 Rhine, - 4~... 12.. 13 with the altitude, a limit must be reached where water Loire, - 4... 8... 10 will remain in perpetual congelation, independent of Elbe, -- 4... 9... 8 all seasonal influences. This limit is called the snowua -Vil - 93. 12 line, and is found at various heights, according to latiDanube, - 9... 56... 6 Dnieper, - 7. 36... 36 tude, proximity to the sea, and other causes, which Don, - 7... 37... 37 affect the general climate of the region. In the HimaWolga, - 14... 94... 80 leh and Andes, it is found at an elevation of about Indus,- - 11... 72... 133 Scandinavian range, at 3500 feet. Generally, in those ASIA. J Ganges, - 10... 76... 148 countries which are near the equator, the snow-line is AA Yang-tse-Kiang, 21* 138 258 found about 16,000 feet, or three miles above the seaAmour, - 16 164 166 AObi, - - 15... 36 79 level: about the 45th parallel in either hemisphere, FRICA. Nile, - p X 18.. 260... 250 it occurs at an elevation of 9000 feet; under 60 degrees AemcA.2 Ella, - -'8*of latitude, at 5000 feet or thereby; under 70 degrees St Lawrence, - 22... 29... 112 latitude, at 1000 feet; and under 80 degrees, the snowAERicA. MLaPlata, - 13... 224 9 490 line comes down to the mean sea-level, for countries [Amazon, X 22a... 395... 1280 which are 10 degrees distant from the poles are covered with snow all the year round. From snow and glacierCLIMIATOLOGY. clad mountains cold breezes rush down to cool the The climatology of the globe relates to the degree of adjacent plains; and similar winds blow from the heat and cold to which its respective countries are sub- arctic to the tropical regions. Indeed, wherever the ject, the dryness and moisture of the air, and its salu- air of one region becomes heated or rarefied, the colder brity or insalubrity as influenced by these and other and heavier air of the surrounding regions will rush in causes. As yet the minutia of climate are but imper- to restore the balance. Such is the cause of all arial fectly determined; the following general causes, how- currents, and in particular of those blowing within the ever, have been sufficiently ascertained: —. The action 25th degree of latitude on either side the equator, of the sun upon the atmosphere; 2. The internal heat known as the trade-winds. leonsoons are merely the of the globe; 3. The height of the place above the sea; trade-winds diverted north or south by the land that 4. The general exposure of the region; 5. The direction lies within these parallels. The simoom, harmnattan, of its mountains relatively to the cardinal points; 6. sirocco, and other local winds, sea and land breezes, and The neighbourhood of the sea, and its relative position; in fact every species of aerial current, may be traced to 7. The geological character of the soil; 8. The degree of similar causes. (See METEOROLOGY.) cultivation which it has received, and the density of The amount of grain which falls on the earth's surthe population collected upon it; and 9. The prevalent face is exceedingly varied, ranging from twenty or winds. These causes, acting together or separately, thirty inches to several feet per annum; but the moisdetermine the character of a climate as moist and ture of a climate does not wholly depend upon the warm, moist and cold, dry and warm, dry and cold, amount of rain registered by a rain-gauge; for some &c.; and this climateric character is the main influence climates are humid, and yet not rainy; others dry, which determines the nature and amount of vegetable and yet subject to periodical torrents. These torrents and animal development. give rise to inundations; hence the peculiar seasonal The torrid zone has two seasons-the wet and the floodings of such rivers as the Nile and Ganges. dry. The latter is considered as the summer, and the former as the winter of the regions within this zone; DISTRIBUTION OF PLANTS AND ANIMALS. but they are in direct opposition to the astronomical The life of the globe-that is, its vegetable and aniseasons, as the rains follow the sun. In some dis- mal productions-constitutes its most important and tricts there are two rainy and two dry seasons every exalted feature as a creation. All the varied mateyear. In the temperate zones, the year is divided into rials of which it is composed, all the complicated the four seasons whose changes are so agreeable and actions, reactions, and mutations to which they are salubrious. This regular succession of the annual subject, are humble phenomena compared with the changes, however, can hardly be considered as ex- production of the lowliest organism. This life is everytending farther than from 35 to 60 degrees of lati- where: the waters teem with it, the dry land from tude. In the frigid zones two seasons only are known pole to pole is clad with it; nay, there is life within — a long and severe winter, and a short but fervid life, and perhaps there exists not a single plant or summer. This abrupt and harsh transition is occa- animal but becomes in turn an abode for others of more stioned by the great length of the day in summer, when diminutive dimensions. Speculations as to the origin the sun never sets, and by the total absence of that and generic classification of vegetable and animal life 63 CHAMBERS'S INFORMATION FOR THE PEOPLE. belong not to our subject. Geography views them under ZOOLOGY. Similar laws are impressed on the simply as they exist, and endeavours to determine the life of the ocean. The whale of the Greenland seas laws which regulate their distribution. is not the same with the whale of the Pacific; the herVegetables —of which about 83,000 species have been ring finds its chosen habitat in the Northern Sea; the described-are regulated in their terrestrial distribu- oyster clings to a peculiar bottom, at a certain depth; tion by conditions of soil, heat, moisture, light, height the cod inhabits the same banks and shoals for ages; of situation, and various other causes; in the waters and a few fathoms of greater or less depth would be by depth, heat, light, nature of bottom, and the pre- more fatal to many species of shell-fish than the dredge sence of mineral and saline ingredients. Were it not of the fisherman. As on plants, so on animals altitude for these causes, there is no reason why the tribes exerts a very decided influence; and we do not exagand genera of one region should not be identical with gerate when we affirm that a lofty mountain range prethose of another-why the palms of India should not sents a more impassable barrier to vital distribution than flourish alongside the oaks of England, the oaks of the widest expanse of ocean. Though presenting aclose England with the pines of Norway, or these again with analogy in the manner of their distribution, plants and the dwarf birches of the arctic regions. As it is, the animals differ in this respect, that many tribes of the tropics have genera unknown to the temperate zone, latter-birds, fishes, and mammalia-make periodical and every advance poleward brings us in contact with nligrations of vast extent; food and proper breedingnew and peculiar species. Temperature iIn this case places being the objects of their search. These migraseems to be the grand regulating condition; and as tions must not be confounded with that adaptability this is effected by elevation, as well as by increase of constitution which fits the horse, the dog, the ox, of latitude, we find the mountain ranges near the the sheep, the pig, and other domestic animals, to be equator presenting all the features of a tropical, tem- the companions and supports of man in his onward perate, and even arctic vegetation. Thus palms and possession of the globe. The one is but a change of plantains may luxuriate at their bases; then appear place in search of food, under a congenial temperature; oranges and limes; next succeed fields of maize and the other amounts to a constitutional change, irrespecwheat; and still higher commences the series of plants tive of climateric influence. peculiar to temperate regions. In temperate latitudes, Mlan, of all animals, has the widest geographical disthough the variety of vegetation be less, similar pheno- tribution. This he enjoys not only from the greater mena present themselves.' We may begin the ascent adaptability of his constitution, but from that superior of the Alps, for instance, in the midst of warm vine- intelligence which enables him to counteract the effects yards, and pass through a succession of oaks, sweet of climate by clothing, houses, fire, and the storing of chestnuts, and beeches, till we gain the elevation of provisions. It may be justly affirmed, therefore, that the more hardy pines and stunted birches, and tread there is no region where man may not exist and carry on pastures fringed by borders of perpetual snow. At on the purposes of life in a higher or lower degree of the elevation of 1950 feet the vine disappears; and at civilisation. Though generally regarded as a single 1000 feet higher the sweet chestnuts cease to thrive; species of a single genus, naturalists have divided man1000 feet farther, and the oak is unable to maintain kind into several varieties, according to their more itself; the birch ceases to grow at an elevation' of prominent physical features; and ethnologists, extend4680, and the spruce fir at the height of 5900 feet, ing the subject according to minor features, language, beyond which no tree appears. The rhododendron and so forth, have subdivided these varieties into ferrugineum then covers immense tracts to the height branches, types, tribes, and families. That the exof 7800 feet, and the herbaceous willow creeps two or ternal conditions to which man, like all other animals, three hundred feet higher, accompanied by a few is subjected, may in the course of ages have stamped saxifrages, gentians, and grasses, while lichens and the inhabitants of certain regions with certain physical mosses struggle up to the imperishable barrier of characteristics, is nothing more than what may be exeternal snow.' Besides these great climatic effects, pected; but that every little difference of dialect, every there are others depending on soil, moisture, light, &c. tint of skin or colour of hair, every mould of nose or which, though limited, are not less imperative. Thus contour of skull, is warrant sufficient for a new subthe southern slope of a hill is generally clothed with division, is an absurdity not to be tolerated. At prespecies distinct from those on the north; a limestone sent, five great divisions are admitted by ethnologists, district presents a carpet of vegetation widely different and these we shall merely enumerate-premising that from that of the clayey moorland: some tribes flourish the brarnches, types, tribes, and families into which in the moist valley, which would die on the open plain; mankind have split in their dispersion over the globe, some tribes thrive in the marsh, others on the dry up- the causes and modes of that dispersion, and other land; some luxuriate under the influence of the sea kindred particulars, will be fully treated in a separate spray, which would be instant destruction to others. sheet, devoted to the PHYSICAL I-IISTORY OF MAN:But whilst most species are subject to these laws, there 1. The Caucasian variety, inhabiting Turkey, Arabia, exists in the constitution of many a certain degree of Persia, part of Tartary, Affghanistan, and Hindoostan elasticity which admits of their adaptation to a wider in Asia; Egypt and Abyssinia in Africa; and the whole range-a beneficent arrangement, which permits man of Europe. 2. The Mongolian variety, spread over the to extend through cultivation those grains and fruits north and central parts of Asia, China, Japan, Birmah, upon which his subsistence so essentially depends. [For Annam, Siam, Cochin-China, and according to some further and more minute information respecting the ethnologists, comprising the Esquimaux both of the laws which regulate the dispersion and distribution of Asiatic and American continents. 3. The Americans plants, see VEGETABLE PHYSIOLOGY.] variety, comprising all the aboriginal races which The animals which people the globe are subjected peopled the new world before its discovery by Columto somewhat similar laws of distribution. Some are bus. 4. The Ethiopian race, inhabiting the whole of strictly tropical, others confined to the temperate zone; Africa, with the exception of Egypt, Abyssinia, and the while not a few are destined to find their subsistence northern coasts. And 5. The Malay race, which is made wholly within the polar circles. Besides this general to include the native inhabitants of the Malaysia, Podistribution, we find a more particular restriction to lynesia, and Australasia. certain continents and tracts where peculiarities of soil, Such are the recognised varieties of the human race; climate, and food, seem to be the governing conditions. and here it may be remarked, that in whatever stage Thus the elephant roams only in India, Birmah, of civilisation they now appear, the time seems to be and Africa; the ostrich in Africa; the rhea in the approaching when some of them will altogether vanish, pampas of South America; the kangaroo in New their place being occupied by the higher and more Holland; the reindeer within the arctic circle; intelligent - a result quite in consonance with the the polar bear amid the snows of Greenland and whole scheme of creation, whether in its physical or Labrador; and so on, as will be more minutely shown social progress. 64 VEGETABLE PHYSIOLOGY. EVERY one must be acquainted with the common forms the slightest touch. In like manner the pith of young of vegetation-herbs, shrubs, trees-for they exist in trees and shrubs has been compared to the spinal marall situations suitable to their growth, and constitute row of animals; the upward current of the sap in not only a highly ornamental covering to the surface spring, and its descent in summer or autumn, to the of the earth, but, as is well known, afford an inex- circulation of the blood; and the exhalation of oxygen, haustible supply of nourishment to the animal races. and absorption of carbonic acid gas in the leaves, to The science which embraces the study and investiga- respiration; but beyond a faint analogy, there is notion of the vegetable kingdom is known by the name of thing like identity between the respective functions of BOTANY, friom the Greek word Botanie, a plant. That plants and animals. Indeed, all the vital functions of department of the subject which explains the organisa- plants are performed in a, manner different froml those tion and vital functions of plants we call Vegetable of animals; the instances of locomotion, sensitiveness, Physiology, and that which recognises their arrangement and power of digestion in the former being very rare and into orders, tribes, genera, and species, according to imperfect, while the power of propagating by division in their respective forms and qualities, Systematic Botany. the latter is equally so. On the whole, the two systems The one relates to functions which are common to all of life seem to start, as it were, from a common point vegetables, the other takes notice only of such peculi- at the base, the inferior forms bearing a certain simiarities and attributes as serve to distinguish one indi- larity in structure and functions, which gradually disvidual from another, or one family from another family. appears as we ascend in the scale of development. It is to the former of these departments that we now Plants derive their food partly from the soil and direct the attention of the reader. partly from the air; and whatever they take must either be reduced to a liquid or to a gaseous state. GENERAL ECONOIMY OF VEGETATION. The ultimate elements of which plants are composed Natuere and Fultctions of Plants.-Minerals, plants, are-carbon, oxygen, hydrogen, and nitrogen. Of and animals are all formed by the chemical combin,%- these, carbon, which is a solid substance, is the printion of certain elementary substances. In minerals cipal; and as it is insoluble in water, it must be comthese elements combine by the force of chemical affinity bined with oxygen, so as to form carbonic acid gas, ollly, but in plants and animals they are held in com- before it can be taken up by plants. Oxygen is the bination by vital action. Of the nature of life, or the next in abundance, and it is absorbed principally when vital principle, science does not attempt to explain the combined with nitrogen, in the form of atmospheric cause, but restricts itself to a imere exposition of its air. Hydrogen is not found in a free state in the phenomena. Vitality enables plants and animals to atmosphere, and therefore it can only be taken up by absorb and assimilate food, consisting of the elements plants when combined with oxygen, in the form of necessary for their increase, and also to reproduce water, or with nitrogen, as ammonia, in which last beings of their own kind, by means of certain organs: form it exists in animal manure. Nitrogen, though hence they are said to be organisecl, and the substances found in very small quantities in plants, is an imporof which they are composed are known by the general tant element, as it constitutes thle principal ingredient name of organic matter. Minerals not possessing vita- in the gluten, which is the most nutritive part of corn lity have no organs, and consist, therefore, of isnorganqic and other seeds, and which is essential to the germinavattcr. Animals feed partly on other animals, and tion and nourishment of young seedling plants. Nitropartly on plants; and plants feed partly on organic gen also appears to be a principal agent in the producmatter when decomposed, and partly on inorganic. tion of colour in leaves and flowers, especially when Thus mineral substances, by the beautiful economy of they first expand. As oxygen is imbibed by plants ihn nature, contribute towards the support of animals combination with all the other elements of which they through the medium of vegetation. are composed, it is not surprising that the plant takes The simplest forms of life are observable in certain up more of this gas than it requires; and consequently, plants and animals, whose economy is limited to the it has been furnished with a remarkable apparatus in absorption and assimilation of nutriment, and the the leaves to enable it to decompose the carbonic acid power of reproduction; and the difference between and other gases which it has absorbed, and to part these inferior forms is so trifling, that in them the ani- with the superfluous oxygen. Plants are thus found mal and vegetable kingdoms seem to pass into each to improve the air by the removal of carbonic acid, other. Thus certain tribes of zoophytes, and some which is injurious to animal life, and by the restorakinds of alge, or sea-weed, are so very nearly allied tion of oxygen, which is favourable to it; and so to both in appearance and habits, that they can scarcely maintain a necessary equilibrium in the atmosphere, as be distinguished from each other scientifically; and, animals are continually absorbing oxygen, and giving indeed, the same object has been occasionally classed out carbonic acid. In hot swampy countries, however, as a plant by one naturalist, and as an animal by an- where vegetation is extremely rapid, and the soil surother. The scientific differences between plants and charged with decaying vegetable matter, plants absorb animals are indeed difficult to define, when they are to more carbonic acid than they want, and give out the be applied to all plants and to all animals. Few plants superfluity through their leaves; hence warnm moist possess the power of locomotion; but the aquatic plant climates, such as those of some of the West India called the Fresh-water Sailor detaches itself from the islands, though extremely favourable to vegetation, mud in which it grows originally, and rises to the sur- are highly injurious to human life. face of the water to expand its flowers. Plants are Light being essential to the decomposition of carbonic propagated by division, which most animals are not; acid gas in the leaves, oxygen is not exhaled by plants but the polypes of the coral-reef grow united like the during the night; but, on the contrary, a small quantity buds of a plant clustering round a common stem from of carbonic acid gas escapes, and oxygen is absorbed. which they receive their nutriment, and, when sepa- These processes have been called the respiration of ated, become each perfect individuals. Plants are plants; but they are very different from the respiration said to have no stomnach; but the lobe-like leaves of of animals, the first being mechanical, and the second Venus's fly-trap possess the power of digesting the flies chemical, and both totally unconnected with the assithey catch; and though plants are said to be without Pmilation of food. When the soil abounds in carbonic feeling, the leaves of the sensitive plant shrink from acid gas and in moisture, the roots of a plant must No. 5. 65 CHAMBERS'S INFORMATION FOR THE PEOPLE. continue constantly absorbing that moisture mixed ascends, it becomes sweet; the starch is changed into with the carbonic acid; and this carbonic acid rising sugar, and this sugar, again, into woody fibre as the to the leaves, escapes in its original state when there tip of the plant emerges into light. When the store is no light to decompose it. The absorption of oxygen of starch and gluten has been exhausted, the plant is is a chemical process, which appears to go on whenever able to subsist by its own assimilating powers, at the the process of assimilation has ceased-in dead plants expense of the air and the soil. as well as in living ones. When leaves have ceased Heat, though essential to germination, is injurious, to act in decomposing carbonic acid, and assimilating unless it be combined with moisture. A high degree or fixing the carbon in autumn, oxygen is absorbed so of dry heat will parch seeds, and destroy their vitality; rapidly as to change their colour to some shade of red; hence, when they are to be kept for food, it is not fruit, when fully swelled, ceases to assimilate carbon, unusual to dry them in an oven, to prevent them from and becomes intensely acid by the absorption of oxygen; germinating. When combined with moisture, a very and, finally, the decay of all vegetable texture is high temperature is not injurious to vegetation; and, hastened by the absorption of the same element. Thus, indeed, some kinds of moss have been found growing as the assimilation of carbon ceases during the night, near hot springs in Cochin China, where they must oxygen is absorbed at that period in quantities that have vegetated in a heat equal to 186 degrees; on the varyaccording to the nature of the plant; those plants other hand, in cold climates, mosses, some kinds of which have acid, or highly-flavoured juices, absorbing grass, and chickweed, are found to vegetate at 35 demost. - Baron Liebig tells us that the tasteless leaves grees, or even only just above the freezing -point. of the American aloe (Agave), if kept in the dark Warmth is not only necessary for the germination of twenty-four hours, absorb only 0'3 of their volume of the seed, but also for the growth and after-developoxygen in that time; while the leaves of the spruce ment of the plant. The sap will not rise without a fir, which contain volatile and resinous oils, absorb ten certain degree of heat; and it is well known that frost times, those of the common oak, which abound in stops its current. Cold will also check the development tannin, fourteen times, and those of the balsam poplar, of the flowers and fruit, and even of the leaves, and twenty-one times, as much. The chemical action of will prevent the full flavour being attained by the oxygen on vegetation is strikingly exemplified in the fruit. The secretions of plants are diminished by leaves of a species of navel-wort, which are acid in the cold. The fruit of the walnut and the beech produce morning, tasteless at noon, and bitter at night. The oil in the south of Europe, which it will not do in Briacid is caused by the accumulation of oxygen during tain; and the leaves of the mulberry grown in this the night, the noonday insipidity by the mixture of country will not afford the same quantity of caoutchouc the oxygen with hydrogen, and the nocturnal bitter to the silkworm as in France and Italy. flavour by an excess of hydrogen. Moisture must be combined with heat and air to Development of Vegetable Life.-This depends upon the render it useful to vegetation. An excess of moisture concurrence of certain agents, the principal of which without heat, and combined with air, induces decay in are-heat, air, moisture, light, and soil. No seed can seeds, instead of exciting them to germinate; and an germinate without the concurrence of the three agents excess of moisture is injurious even to growing plants, of heat, air, and moisture; but in the ysozsth of plants, as it destroys the delicate tissue of the spongioles of the agency of soil and light is also necessary. Every their roots. When trees are grown in situations where perfect seed contains the germ or embryo of a new they have abundance of heat and moisture, but where plant of the same kind as the parent, and a portion of the roots are beyond the reach of air, they have a tenconcentrated carbon and nitrogen, in the form of starch dency to produce leaves instead of fruit and seeds, and and gluten, laid up to serve as nutriment for the all their secretions are weakened. On the other hand, young plant, till its organs are sufficiently developed to too little moisture prevents the leaves and fruit from enable it to seek food for itself. The seed is generally attaining their proper size and form. enveloped in a hardened case, in order to preserve it Air is essential both to the germination of the seed in an inert state as long as may be necessary. As soon and the development of the plant. Without oxygen as a bean, for example (see fig.), is put into the ground, from the atmosphere, the carbon laid up in the seed it is acted upon by the influence of heat and mois- cannot be made available for the use of the infant ture, which distend its particles, and make them burst plant, as carbon in its concentrated state is insoluble the integument that envelopes them. The agency of in water, and requires to be combined with oxygen to b6,, the air is next required to convert it into carbonic acid gas, before it can be combine with the store of absorbed by the vessels. In like manner, air is essen-, x nutriment laid up in the tial through all the processes of vegetation; no wood seed (a a), and to fit it for can be formed, no seed ripened, and no secretions pro-,.. In.,y l,,: the purposes of vegetation. duced, without abundance of carbon; and this cannot t;S00!l~t $\ 1The first organ which ex- enter the plant, even from the soil, without a constant a' i\, i pands in the embryo of a supply of oxygen from the air. The greater part of the i. young plant is the root c; carbon in plants is indeed derived directly from the'~~ ), By;\; i.[ and nature has provided a air by the leaves, in the shape of carbonic acid gas-a small opening in the co- minute quantity of which is always found in combi1;'It/ X vering of a seed, towards nation with the atmosphere. which the point of the root Light is not required for the germination of seeds, is always turned, in order but it is essential to the development of plants, as it that it may be protruded occasions the decomposition of the carbonic acid conwithout injuring its soft tained in the vessels of all the parts exposed to its inand delicate texture. The fluence; without which the plant could not assimilate root takes up water and the carbon to its own use. Colour also appears to air, and transmits the li- depend partly on light. Plants grown in darkness are quid thus formed to the seed-leaves b, in which it most deficient in colours which contain blue. The is exposed to the influence of light. The nutritive leaves and other parts, which should be green, are fresubstances laid up in the seed become quite changed quently reddish, from the retention of oxygen; or yelduring the process of germination. The starch, which lowish, from the superabundance of nitrogen; while the is insoluble in water, is rendered soluble by the ac- flowers and fruit are whitish. Frequently, the whole tion of a peculiar substance called diastase, derived plant appears whitish, and of a sickly aspect, in which firom the gluten. This substance has so powerful an case it is said to be etiolated, or blanched. effect upon the starch, as to render it instantly soluble The soil serves not only as a bed for plants to grow in the sap, and thus the nutriment is gradually pre- in, but also contributes to their nourishment. In addipared for the use of the infant plant. As the sap tion to the elements of which they are principally VEGETAB3LE PHYSIOLOGY~ composed, there is always found in their substance a kind of earth may succeed in the same soil, after it small quantity of inorganic matter, which differs ac- has become unproductive for the first kind of crop. cording to the nature of the plant, and which appears This, according to modern doctrines, explains the neto be derived solely from the soil. The proportion cessity which is known to exist for what is called the which this matter bears to the whole will be found by r otation of clrops-that is, for letting crops of a different burning part of the plant in the open air; when the nature succeed each other in fields and gardens. The inorganic matter, being indestructible by fire, will be necessity for this rotation was supposed by Decandolle left in the form of ashes. Soils are of various kinds, and others to arise from plants poisoning the soil with and they are produced principally by pulverised par- the excrementitious matter which they were supposed tides of rocks being disengaged by the action of heat, to eject by their roots; but while this hypothesis was air, and water, and mixed with decaying animal and believed, it appeared difficult to account for the wellvegetable substances. There are four primitive earths, known fact, that the samle crops may be grown perfectly called clay, saed, lime, and mgnagnesia; the first three well in any soil for an indefinite number of years, proof which are found more or less in almost every soil, vided that soil be frequently and properly manured; and generally with only a very small proportion of the that is, supplied afresh with the ingredients of which latter. Clay, which is also called alumina, or argilla- it has been exhausted by the plants. As to the matter ceoas earth, or earth of alum, predominates in some which is discharged from the roots, it is generally of soils, and these are generally unfertile, as the particles the same nature as the peculiar secretions of the plant of clay are too adhesive to allow the free passage of -as, for example, the matter exuded by the roots of either air or water to the roots of plants. A soil of this the poppy exhibits the properties of opium-and can kind also offers obstacles to the expansion of fibrous exercise no deleterious effect upon its growth in the roots; and when it admits water, it retains it so long manner Decandolle supposed. as to be injurious. Sand, which is also called sile, Nature, when unassisted, invariably makes an effort silica, or siliceous easrth, consists, on the other hand, of to change the crops of plants. When a forest in North particles which have generally too little adhesion to America is burnt down by accidental fires in the sumeach other; and it is injurious to plants, partly from mer season, trees of quite a different kind spring up its incapability of retaining sufficient water for their from long concealed seeds in place of those which have nourishment, and partly because it admits too much been destroyed. When, in ordinary circumstances, one solar heat to their roots. Lime is never found in a kind of plant has exhausted the soil in its neighbourpure state in nature, but always combined with some hood, it pushes its roots to as great a distance as posacid. The common carbonate of lime, or limestone, sible in quest of food, and there sends up shoots, while is of no use in vegetation till it has been burned- a new race of plants grows upon the spot which it has that is, till the carbonic acid, water, and other mat- vacated. In these, as in a thousand other circumters it may contain, have been driven off by heat. stances, we find that one of nature's great primary laws In this state it is called caustic lime, and is used as a is that of perpetual change-an alteration from one manure, as it has a great affinity for carbonic acid, condition and appearance to another, in endless sucwvhich it is continually drawing into the soil from the cession and variety. In the artificial cropping of the atmosphere or other sources. Chalk, or the earthy ground, the farmer, for his own sake, is impelled to carbonate of lime, is well adapted for vegetation, but take a lesson from nature, and to study what species it is generally cold, as, from its whiteness, it reflects of plants he can most advantageously produce in sucthe solar rays instead of absorbing them. Magnesia cession from his fields. (See AGRICULTURE, p. 491.) is very similar to lime, but is less abundant. It gene- Term of Vegetable Existence.-The longevity of plants rally occurs in combination with lime, in what is called differs according to their nature, and the circumstances magnesian limestone. Notwithstanding the whiteness in which they are placed. Thus herbaceous plants, the of chalk, calcareous soils-that is, soils containing some stemrs of which are succulent and full of juice, are form of lime-are generally black, from the quantity either annuals, that grow only one season, and die as of vegetable matter which they contain in proportion soon as they have ripened their seed; bienszials, which to the depth of the soil. All soils containing a great generally last for two years; or perennials, which last proportion of decayed vegetable matter are black; and for several years. Trees and shrubs, which have ligblack soils, though generally warm, from the power neous or woody stems, are destined to remain undlethey possess of absorbing solar heat, are seldom pro- cayed for years. Shrubs are those ligneous plants ductive, unless they be dry. Thus black peat, or bog which have several stems springing from the same root, earth, which is moist, is unproductive; while heath all nearly of the same thickness. They seldom last mould, mixed with sand, which is dry, is very useful above thirty or forty years, and frequently not half for many kinds of crops. The reason is, that decayed that time; but trees, which have only one stem or trunk vegetable matter, or husmus, is insoluble in water, and proceeding from the root to a considerable height before consequently cannot be taken up by plants until the it divides into branches, generally endure for a long carbon it contains is combined with oxygen, so as to period of time-in several instances even for centuries. form carbonic acid gas, which can only be done when the The length of time which trees live depends in a great humus is kept sufficiently dry to allow of its particles measure on the situations in which they grow. If a being exposed to the free action of the atmosphere. tree which is a native of mountains be placed in a valIt must be observed, that no soil consists of any one ley, it grows more rapidly, but the term of its existence of the primitive earths alone, and that most soils con- is shortened, and its timber becomes softer and of less tain all of them combined in different proportions, and value. In like manner, if the tree of a valley be grown mixed with other ingredients. These are saline par- on a mountain, the term of its existence is lengthened, ticles of various kinds, potash, soda, and other alkalies, and its trunk, though of slow growth and small dimeniron, and several other minerals, in combination with sions, produces timber remarkable for its toughness and the different acids-all of which are designated, when durability; as, for example, the Highland oak. speaking of the food of plants, by the general name of The age of trees was formerly calculated by their inzorganic matter. Plants require different kinds of in- diameter, or by the number of concentric circles or organic matter, according to their nature, and appear layers in the trunk; but both these modes are now to possess the power of selection, as they only take the found to be fallacious. According to the first, it was kind they need, though it may form but a very small supposed that if a tree attained the diameter of a portion of the soil in which they grow. Thus it is foot in fifty years, fifty years should be counted for evident that any particular crop must in time exhaust every foot it measured in diameter; and thus it was the soil in which it grows of the requisite inorganic supposed that the great baobab-tree, found by Adanmatters, unless they should be renewed by the addi- son on the banks of the Senegal, which measured tion of what are called mineral manures (see AGRICUL- nearly thirty feet in diameter, must have been about TURE); and it is also clear that crops requiring another six thousand years old, or coeval with the world itself. 67 CHAMBERS'S INFORMbATION FOR THE PEOPLE. It is now found) however, that the baobab, like all miatised —that is, may be macde to grow and propagate soft-woodecl trees, grows rapidly, and attains an enor- their kind in a region in which they do not naturally mnous diameter in less than a hundred years. The occur. Many of our cultivated and most useful plants mode of counting by concentric circles only applies are of this kind; as, for example, the potato. This to exogenous trees, and even with them is very un- plant, which is a native of tropical America, flourishes certain, A warm spring, which sets the sap early in luxuriously, and is of the highest utility, in northern motion, followed by weather cold enough to check Europe; but this it does by a special adaptation. In vegetation, will give the appearance of two layers in South America, the warm climate enables it to propaone year, as the recommencement of vegetation will gate by the seed; hence in that region its tubers are have the same appearance as a new layer in spring. small and insignificant; but in Europe, where the cliIn many trees, such as the oak, for example, a second mate is unfavourable to the production of the plant growth often takes place after midsummer; so that from seed, it propagates by the tubers, which are conseeven a third layer is occasionally formed in the course quently enlarged, so as to contain a store of nutriment of six months. On the other hand, a moist warn winter, for the young plant, before its stem and leaves be by keeping the tree growing the whole year without sufficiently developed. The acclimatising of plants any check to vegetation, does not permanently change their character, for, in -will give the appearance being restored to their native habitats, they assume of only one layer to the their original forms and qualities. growth of two years. Not- The habitats of plants-that is, the situations in withstanding these ano- which they naturally thrive best-are generally distin-,'/ A1 ~',' Smalies, practical men find guished as follow: —Maisne when the plants float upon, i ITUPIN i counting the concentric or are imnmelrsed in, salt-water, such as sea-weeds; circles of a tree the best and mnaritime when they grow by the sea-shore, or in mode which has yet been places expyosecl to the influence of the sea - breeze..'%'"~'"' ~'";.. discovered of ascertaining Aquatic is the general term for fresh-water habitats; its age, as in ordinary aind these may be either lacustrisne when growing in cases only one growth is lakes, J'ltviatile when in rivers, or pahsstrine when in made in the course of a marshes or wet meadow-lands. Plants growing in open yeaor. The accompanying figure represents a section pastures are said to be prateinsise, in cultivated lands of a stem five years old, having the pith in the centre, am'vessine, in woods sylvan, in mountainous parts alpize, a' cylindrical layer for every year of the growth, and the and in caves, mines, and other underground excavabark on the outside. tions, suzbterranean. The station of a plant is said to The natural ldecay and death of plants appear to be epiphyte when it grows upon others, living or dead, follow the same laws as the natural decay and death without deriving from them the elements of nutrition; of animals. When a tree approaches the term of its and parasitic when it adheres to their surface, and existence, the sap flows more feebly through its vessels, directly extracts its nourishment. The range of habitat and it is no longer propelled through every part. As is that extent of the earth's surface over which a plant this takes place, the parts no longer visited by the sap is distributed by nature. The terms maritime and die; and as soon as life has fled, the opposite prin- alpine, for example, are general in their application, ciple of chemical affinity begins to act, and the various anld refer to all plants which grow by the sea-side or elements which composed the plant fly o:f, to enter on mountains; but the plants which flourish on the into new combinations. This is the natural process sea-shores of Great Britain are not the same with those which takes place invariably with every organised on the coast of Africa; nor are these, again, allied to being; the fall of the leaf, and the dropping of the the mnaritime vegetation of Chili. The geographical ripe fruit, are but the death of both when fully ma- range of any plant conveys a more specific idea, and tured; and in like malnner death is followed in both embraces only that particular spot in which the plant instances by its natural attendant-decomposition. rejoices. This range is circumscribed by conditions of )ISTRIB3UTION OF PLANTSemperiature, light, and elevation above the sea, and does not, as might. be supposed, depend very closely The geographical arrangement of the vegetable upon belts of longitude, by which temperature is geneworldc is influenced by conditions of soil, heat, mois- rally indicated. Thus nearly all the beautiful pelarture, light, altitude of situation, and various other goniums andcl mesenibryanthemulms which adorn our causes; for, did they flourish independently of these greenhouses, are natives of a limited space near the conditions, then there were no reason why the vege- Cape of Good Hope, as are afso many of our most tation of. one part of the globe should differ from beautiful bulbs. The curious stapelias, that smell that of another. We know, however, that the flowers, so much like carrion, are found wild only in South shrubs, and trees which adorn the plains of India Africa. The differenlt kinds of eucalyptus and eperis are not the same with those which clothe the val- are restricted to Australia; and the trees bearing balleys of Britain; and that these, again, are totally sam grow principally in Arabia, and on the banks different from the scanty vegetation of Iceland or of the Red Sea. The umbelliferous and cruciferous Spitzbergen. Each order is, nevertheless, perfectly plants spread across Europe and Asia; the cacti are adapted to the conditions under which it exists, and found in tropical America; and the labiatce and cariofinds in its habitat, or native situation, all the ele- phyllacese are seldom discovered but in Europe. The ments which administer to its growth and perfection. peculiar ranges and centres of vegetation, as they Obvious, however, as are the effects of these external are termed, cannot be sufficiently understood, however, conditions, the mode in which they operate is but im- without a knowledge of the different tribes and classes perfectly known. The sanme elements enter into the of plants, the consideration of which forms the subject composition of the vegetation of the tropics as those of SYSrTEimTIC BOTANY-p. 81-112. which form the vegetation of temperate regions; the Soil exercises less influence on the distribution of same organs, tissues, modes of growth, and inflores- plants than is usually ascribed to it, though there can cence, are observable; and yet, without the conditions be no doubt that'on its power of absorbing and retainabove enumerated, a plant which has been transferred ing heat and moisture much of the luxurious growth from the one region to the other will speedily languish of vegetables depends. They will grow to some degree and die. Even one which flourishes under the influ- in almost any soil, as the bulkier ingredients (clay, ence of the sea-breeze, if removed far' inland, will lime, and sand) always predominate; but a proper perish; and no art can retain in healthy perfection a proportion of these earths is necessary to perfect vegenative of the mountain which has been transplanted tation; and many plants will not continue healthy to the warm and humid valley. and propagate, unless supplied with other elements, Certain plants, like animnals, may, however, be accli- such as potash, soda, and various metallic salts. For 68 VEGETABLE PHIYSIOLOGY, this reason the natural vegetation of a limestone coun- the elevation of 1950 feet the vine disappears; and at try differs from that of a retentive clay; while the 1000 feet higher the sweet chestnuts cease to thrive; plants which cover all sandy downs are totally different 1000 feet further, and the oak is unable to maintain in kind and character from those of the alluvial valley. itself; the birch ceases to grow at an elevation of" 4680, Moisture, which is indispensable to the existence of and the spruce fir at the height of 5900 feet, beyond vegetation, also exercises soume influence in its natural which no tree appears. The rhododendron ferrugineum distribution. The plant which roots in the parched then covers immense tracts to the height of 7800 feet, sanlli is furnished with leaf-organs to absorb moisture and the herbaceous willow creeps two or three hundred from the atmosphere, and retain it, while in a wet feet higher, accompanied by a few saxifrages, gentians, situation these organs would become diseased, and rot and grasses, while lichens and mosses struggle up to away; so, in like manner, a marsh plant, whose spon- the iiperishable barrier of eternal snow.' gioles are its main organs of sustenance, would perish The circumstances which facilitate the dispersion or were it removed to an arid soil. The organic structure migration of plants, are unconnected with the causes of such plants forms a limit to their distribution; and which limit their geographical distribution. Many seeds the same may be said of the salicornie, arenaria, pe- drop from the parent stalk, spring up into new series of ploides, &c. which live only when exposed to the salt stems, which in turn give birth to another race of seeds, spray of the ocean. Another circumistance connected and these again to another circle of vegetation. Thus with the air, and one which is worthy of notice, is any tribe of plants would spread frol a common centre whether it be more generally stagnant or in motion. till arrested by the influences which limit its range of It is perfectly evident that the action of stagnant air habitat; and this mode of dispersion no doubt occaupon a plant must be every way less than that of mov- sionally occurs. In most plants, however, the seeds are ing air, whether we suppose the action to be of one small and light, and easily borne about by the winds; kind or another; and therefore, up to a certain point, some are downy, and furnished with wings; others motion in the air must be favourable to the growth of have tufts and filaments; and many are ejected from vegetables. Of this we have abundant proofs in tile their carpels with considerable force. All these apvariety, luxuriance, and activity of the vegetation of penclages and peculiarities are evidently intended to those regions which, like the Brazils, Oriental isles, facilitate their dispersion, which is further assisted by and Malay peninsula, are constantly exposed to the rivers, lakes, and tidal currents, bythe wool of animals, steady currents of the trade-winds. the droppings of birds, and the economical pursuits bf H-Ieat and light are perhaps the most manifest agents man, whether accidental or intentional. The seeds are in the distribution of vegetable life. The luxurious arrested in their progression by various causes: sosie growth of the tropical jungle is the direct result of are furnished with barbs and hooks, which lay hold of warmth and moisture, just as the barrenness of Nova objects; others become entangled amid herbage, the Zembla is the effect of piercing cold; yet both situa- mud of rivers, or the softened soil of winter; while tions are inhabited by plants which enjoy the condi- many, towards spring, are acted upon so as to emit antions peculiar to their existence. No conditions of adhesive substance, or their fleshy pericarps melt down mere soil, or light, or moisture, could make the palms, into the soil, carrying the embryo along with themn. tree-ferns, and jungle-flowers of India, flourish in Great Britain; so neither would our oaks or pines flourish STRUCTURE OF PLANTS-SI-IPLE ORGANS. in Iceland, unless we could provide for them that The organs with which both plants and animals are temperature and seasonal influence necessary to their gifted to enable them to carry on the functions of life, healthy existence. Light, though it acts most power- are of two kinds-naamely, simple oesarns, such as the fully on the colours and blossoms of plants, is also an flesh of animals and the cellular tissue of plants; -and essential element in their geographical arrangement. consposund orgaess, such as the leaves of plants and the The southern slopes of our hills and mountain ranges limbs of animals; the latter always consisting of cerare always clothed with a more elaborated and more tain arrangements or combinations of the former. The fully-developed race of plants than the northern slopes; principal substance of which plants are composed is and this depends wholly upon the greater degree of known by the general naule of tissue; but of this there light which the former enjoy. The northern side may are three distinct kinds, distinguished as cellular, swoocy, sometimes be as green, but it never will be so flowery and vasculare, which have been compared to the flesh, as the southern exposure; and the attentive observer bones, and veins of animals. may detect new tribes on either side almost as soon as Cellclac' tisssue is the fleshy or succulent part of plants, he has passed the summit. The more free the expo- of which familiar examples may be given in the pulp sure, the more readily will most plants also blossom, of leaves and fruits. It consists of a great number of and yield a rich fruit. So well is this understood in cells of irregular shape, which adhere together, somethe grape countries on the Rhine, that the right bank times quite loosely, as in the pulp of an over-ripe of that river, which faces the sun, is reckoned to be orange; and at other times-as, for example, in the much more valuable than the left, and commands a cuticle or outer skin-so closely, as to seem to form higher price for its wines. a homogeneous mass, unless examined by a powerful Altitude, or elevation above the ordinary sea-leIel, microscope. Each cell consists of a small bag or bladalso exerts an obvious influence on the distribution of der, filled apparently with liquid; but intermixed with vegetable life: it is equivalent to removal from a tro- this liquid, which consists of hydrogen and oxygen pical to a temperate region, or from temperate latitudes nearly in the same proportions as in water, there are to the arctic circle. For every hundred feet of ascent, some grains of starch and some of colouring matter, there is a proportional fall of the thermometer; so that, surrounded by a few particles of gluten. The starch, at the height of 5000 feet in Britain, and 16,000 at the equator, we arrive at the region of perpetual snow; in other words, to heights as destitute of vegetation as the frozen zone. This intimate relation between altitude,. i, arid declease of temperature accounts for the fact, w hy the base of a mountain may be clothed withed with vegetation of tropical India, the sides with that of temppe-, rate England, and the summit with the mosses and I lichens of icy Labrador.'We may begin the ascent CS of the Alps, for instance, in the midst of warm vine- 2QK2 ) { yards, and pass through a succession of oaks, sweet chestnuts, and beeches, till we gain the elevation of the a b more hardy pines and stunted birches, and tread on which has been compared to the fat of animals, consists pastures fringed by borders of perpetual snow. At principally of carbon, and the gluten of nitrogen. The 69 OHAMBERS'S INFO!RMIATION FOR THE PEOPLE. cells of cellular tissue vary very much both in size and each of these exceedingly slender fibres is, in fact, a shape. They generally, however, present the appealr- hollow tube tapering at both ends, and adhering to ance of a honeycomb (a), when sections are cut of the other hollow tubes of a similar nature. The tubes of pulp of the leaves, pith, or fruit; but in sections of the woody fibre, when young, serve as channels for the bark and sapwood, they take a parallelogram form, passage of the ascending sap; but afterwards they and resemble the bricks of a wall (b). The cells are become filled with particles of inorganic matter, which generally small when they are first formed, but they give solidity and durability to the wood. Woody fibre increase in size as they become older. Thus in the is found mixed with cellular tissue in the wood and tissue of a leaf they are at first very small; but as inner bark of trees; it also forms part of the veins or fresh cells are formed close to the veins, those towards nerves of leaves; and in general is found in all organs the margin of the leaf dilate; and a similar process which require strength, toughness, and durability. takes place in every part of the plant, the newly- Vascular tissue has been divided by modern botanists formed tissue always consisting of cellules, which en- into three varieties-namely, vascular proper, pitted, large as they get older. and lactiferous. Vascular tissue, properly so called, In the pulp of leaves and fruit, and in the cellular consists of cylindrical cells of great delicacy and thintissue of the bark, there are frequently cavities found ness, called spiral vessels and ducts. Spiral vessels conamong the cells, which are of several kinds. Those sist of hair-like tubes coiled round and round in a called receptacles of secretion are formed for the recep- spiral manner, and enclosed in tubes of transparent tion of the oils and other fluids secreted by plants; as, membrane. They are of a light elastic nature, and for example, the fragrant oil in the myrtle and the though coiled up naturally like a cork-screw (see fig.), orange, and the turpentine in the pine and fir tribe. they may be unrolled to a considerable extent. If Other similar cavities, called air cells, contain oxygen a leaf of the spider-work (Tradescantia), or of any nlearly in a pure state; and others, which are called kind of bulb, be doubled down first on one side, and intercellular passages, are generally filled with watery fluid, and communicate with the open air by means of pores in the epidermis. All these cavities have no Spiral Vessel. distinct membrane to enclose them, but are surrounded then on the other, so as to break through the outer by what may be called a wall of small cells, which skin on both sides, and if the two pieces of the leaf be form part of the cellular tissue. The shape and size then carefully and gently drawn asunder,", the transof these cavities vary exceedingly; the receptacles of parent membrane will break, and the spiral vessels secretion, and the air cells, are generally larger than will unrol, so as to appear, when seen with the naked the common cells, but the intercellular passages in eye, like fine hairs between two portions of the leaf. very dry plants are so small as to be scarcely percep- Spiral vessels prevail in leaves and flowers, and are tible; though in succulent plants-the stem of the found, though more sparingly, in the young greenwood garden Nasturtium, for example-they are nearly as of trees and shrubs; but never in the old solid wood, large as the cells. and very, rarely in the roots or in the bark. They Cellular tissue readily decays when the parts comin- are very few and small in coniferous trees; but they posed of it fall from the tree. The carbon it contains are abundant in palms and their allies. In ferns and is libeiated so - soon as the vital force by which it was the club mosses they occur occasionally; but the other retained has fled, and escapes with the oxygen in the cryptogamous or flowerless plants are entirely without form of carbonic acid gas; whilst the hydrogen, which them. These vessels are sometimes called air vessels, then forms its principal remaining element, attracts because their slender spiral tubes are always found fresh oxygen from the atmosphere, and becoming thus flled with a kind of air, which contains seven or eight chaliged into water, rapidly melts away, leaving the times more oxygen than the colmmon air we breathe. inorganic portion to mix with the soil. In leaves, the Ducts are cylindrical tubes closely resembling those pulpy parts disappear first, leaving behind the outer which enclose the air vessels; only the spiral vessels cuticle and the nerves or veins, which are of firmer they contain appear to have been broken into rings, or texture; the latter, indeed, being composed principally short cork-screw-like curves, which sometimes cross each of woody fibre, the tubes of which have been filled with other in a reticulated manner. These rings and curves earthy matter during the process of vegetation, decay are, however, quite different from the true spiral vessels, very slowly. Those parts of a plant which nature seems as they have no power of unrolling, and appear only to have intended not to be of long duration, such as the intended to keep the slender membrane which forms fleshy parts of the leaves, the flowers, and the fruit, are the duct distended. Similar rings are found in the composed entirely of cellular tissue of very loose tex- windpipe of animals, which appear also only intended ture. In the stones of fruit, however, which are also to keep that membrane distended. composed of cellular tissue, a portion of earthy matter Pitted tissue, sometimes called dotted ducts, consists is deposited, which partially lines the cells, and gives of tubes which, when held up to the light, appear full them a temporary firmness, without destroying their of holes, from the numerous dots in the lining of their facility of decay; so that the seeds contained in them sides. The mouths of these tubes are very conspicuous may be preserved as long as they are kept in a dry in the wood of the rattan when cut across; they are state, and yet liberated so soon as they are placed in also to be seen in sections of the oak and the vine; a situation favourable for germination. and indeed in most other kinds of wood, as well as Woody tissue consists of bundles of extremely fine in the stems of herbaceous plants. Being the channels cylindrical cells, tapering at both ends, and of great through which the ascending sap is conveyed, the length and toughness (see fig.). These bundles have dotted ducts are larger than the vessels of the other tissues, and are distinctly visible in many kinds of wood, even when dry. Modern botanists consider them as belonging to cellular tissue, and as consisting only of =_ ~ a~ a =elongated cells placed end to end, and opening into each Woody Tissue, other so as to form a kind of tube. Lactiferous tissue, which is the same as the proper vessels of the older so much the appearance of fibres, that their true nature botanists, consists of tubes, which are distinguished was not suspected by the older botanists; and it was from all other kinds of tissue by being branched. They supposed that they retained their fibrous appearance are filled with a mucilaginous fluid called the latex, even when subjected to the most minute division. It which is, in fact, the descending sap, and is full of is now found, however, that the fibres of woody tissue numerous small specks, like that which is the germ of cannot be divided beyond a certain point; and that, the future chicken in the egg of a hen. These specks though they may be made so small as to take seven are always in motion while they remain in the vessels or eight of them to equal the thickness of a fine hair, of the latex, and whenever they are deposited, they 70 VEGETABLE PHYSIOLOGY. expand into cells of different kinds of tissue. From brier, &c. which are filled with a fragrant volatile oil. the latex also is formed gum, sugar, tannin, or other In both these cases, glandular hairs seem to act as secretions, according to the nature of the plant. The organs of excretion, through which the plant is envessels of the latex are found on the under sides of abled to exude certain fluids. leaves, and within the inner bark, which they may be Glands are organs of secretion, or cells containing said to line: hence the peculiar secretions of a tree liquid different from that in the cells of the common are generally strongest in the bark, tissue of the plant, as in the flowers of the Hypericum, or St John's wort, which give out a red liquid when COMPOUND ORGANS AND THEIR FUNCTIONS, pressed. Sometimes glands assume a wart-like appearThe compound organs of plants are composed of ance; thence the stems or leaves on which they appear several of the simple ones; as, for example, a leaf has are said to be verruecose; and sometimes they take the woody and vascular tissue in its veins, and cellular form of little watery blisters, in which case the plant is tissue in its pulpy part; and in like manner these ele- said to be papillose. mentary organs are found in the stem, flower, fruit, Besides the above- mentioned organs, there are and, in fact, in every part of the plant. The compound prickles, thorns, and spines, which seem closely analoorgans are divided into three kinds-namely, the gene- gous, though much less common. Prichles may be ral organs, which are common to every part of a plant, called hardened hairs, as they are merely indurated such as the epidermis or skin, and the hairs; the organs expansions of the epidermis, without any woody fibre; of nutrition, through which the plant takes and digests and they may be detached from the branch which bears its food, as the root, stem, and leaves; and the organs them without laceration. Thorns differ from prickles, of reproduction, which are the flowers, fruit, and seeds. in being formed partly of woody fibre; and they cannot General Organs. — The epidermis or skin is a thin be detached from the branch which bears them without membrane, which covers every part of a terrestrial lacerating its vessels. They are, in fact, abortive or plant, except the stigma and the spongioles, but which imperfectly-developed buds, and are formed instead of is sometimes entirely or partly wanting in plants which leaves and branches. Spines resemble thorns in every live under water. It is composed of a kind of cellular respect, except in being found on the leaves and stems tissue; but the cells are pressed so closely together, as of herbaceous plants, while thorns only grow on the to make it appear homogeneous to the naked eye; and trunk and branches of woody plants. When spines they are filled with air instead of water. The use of grow on leaves, they are always found on the veins the epidermis is to retain a sufficiency of moisture in which are extensions of the woody fibre. plants; for should the delicate membrane of which the cells of their tissue are composed become so dry as to ORGANS OF NUTRITION. lose its elasticity, the different organs would be unable The organs of nutrition are the root, the stein and to perform their proper functions. On this account its branches, and the leaves; and of these organs, the root thickness is curiously adapted to the conditions under and the leaves, or some modification of them, must which a plant grows. In ordinary cases, the epidermis exist in every flowering plant, as the vital functions consists of two layers, the outer one of which, called could not be carried on without them. the cuaticle, is extremely thin, and consists of cells of The root (radix in Latin) is commonly defined to be oblong shape and large size, pressed closely together, that part of a plant which attaches itself to the soil and filled with air; while the secondary layer is formed where it grows, or to the substance on which it feeds, of cells of a different shape and size, but still closely and is the principal organ of nutrition. Exceptions to pressed together. In the plants of very hot countries, this definition occur, as in the case of some vegetables it consists of three or even four layers, in order that which grow floating loosely in water, as duckweed and the moisture may be retained, notwithstanding the ex- others, having no root at all. As the cessive heat and dryness of the climate. Those plants nourishment of a plant is derived from the rab which have numerous pores, or stomata, in their epi- earth, the root is that part which grows dermis, require watering oftener than others, and are in an opposite direction to the stem, and i more easily affected by the heat of the sun. Thus we is buriedinthe ground. A root consists of often see the leaves of the common lilac droop, as several parts (see section), which have been! though the plant were suffering from want of water; called the body or caudex (a); the collar l while those of the apple or pear-tree which grows beside or life-knot (b); the branches or radicles, it are perfectly unaffected by the heat-the latter tree when such exist; and the rootlets or small not having above twenty thousand pores in the square fibres (c c), which seem to be indispensinch, while the lilac has one hundred and sixty thou- able in all roots. The body of the root sand in the same space. The epidermis of aquatic assumes various forms; it may be globeplants is extremely thin, and is entirely wanting on shaped, as in the turnip; conical, or the under side of floating leaves. tapering gradually from the collar to Hairs are minute expansions of the epidermis, and the attenuated fibre, as in the carrot; c are found almost upon every part of a plant. Some- fusiform, or tapering at both ends, as in times they cover the whole of the leaf, and at others the radish; this latter may be abrupt-that is, as if they are only found on the lower surface. They are of the lower end had been cut off, exemplified in the two kinds-namely, lymphatic and glandular; and are devil's bit scabious; fibrous, or consisting of small described as downy, silky, hirsute, bristly, ciliate, stel- threadlike fibres, which proceed directly from the collate, &c. according to their aspect and mode of arrange- lar, as may be seen in most grasses; tuberous, when ment. The use of lymphatic hairs is partly to protect the fibres bear globe-shaped bodies filled with starchy the surface of the leaf from the heat of the sun and matter, as in the potato; fasciculated, when the fibres from drying winds, and partly to collect moisture from swell slightly in the middle; bulbous, when the round the atmosphere. It is now known that plants take in lobe consists of coats or layers, such as may be seen on nourishment from the atmosphere as well as fiom the cutting an onion across. A corm is similar in form to soil; and it is supposed that part of this nourishment a bulb, but is not composed of layers; a palmated root is absorbed through the lymphatic hairs. It has been consists of a number of oblong tubers proceeding from observed that the hairs, when they do not cover the the collar, like the fingers from the body of the hand, entire surface of the leaf, always grow either upon the as in the dahlia. Tuberous roots, such as the potato, veins or in the angles where the veins cross each other. are considered by some modern botanists as merely It is thus evident that they have a direct communica- underground stems, from the circumstance of their haytion with the vessels containing the sap. Glandular ing eyes or buds from which branches will spring. hairs are hollow, generally open at the point, and with The crown, collar, or life - knot, as it is variously a receptacle of secretion at the base. Of this nature called, is that part which lies between the stem and are the stings of the nettle, and the hairs of the sweet- the root. It is the most essential portion of the whole; 71 CHlAMBERS:S INFORMATION FOR THE PEOPLE. for if it be removed, or seriously injured, the plant will stem of such flowers as the primrose, the daisy, the inevitably die; whilst the small fibres or rootlets, al- snowdrop, and the lily, is termed the scape, though though an essential part of a plant, may be destroyed flower-stalk is certainly better; the running stem, as in at pleasure so long as the crown remains, for it readily the strawberry and cinquefoil, is termed a runner; a reproduces them. When it is of a slender make, as shorter runner that does not root, as in the housethe seeds form, it dries up, ancl the plant soon dies, leek, is termed an offset; a longer one that does not as the poppy, mignionette, and other annuals. The root, as in the cucumlber, a vinelet; and a small stem crown, however, in some cases, by proper treatment, proceeding laterally from a root or stool, a sucker.' may be rendered so strong, that annuals can be brought The stemg it will be observed, assumes many forms to grow for two or more years. The fibrous root con- and characters as to bulk, structure, position, place, sists of a qluantity of long thin -fibres, of different lengths and thicknesses, and having still finer ones springing from them, as in the case of wheat, barley, and most grasses. These small fibres or rootlets bear a resemblance to the branches and leaves of the stem. {? Fibrils consist of a central fasciculus of vessels, enclosed 1 by a cellular cortex and cuticle. Likle the leaves of trees that are not evergreen, they are annually pro- duced; in some cases dying and falling off like leaves,:!. in others becoming thicker, harder, and. formng radicles or root-branches. The spongelets, as they are called, which take up nourishment from the soil, are situated at the extremity of these rootlets. They are minute spongy bodies, of an oblong shape. We have an instance of rootlets falling off like leaves in those 1. 2. 3. 4. arising from bulbs-such as the lily, the onion, the and duration. It appears as a tuber (Gladiolhs, i), tulip, &c. which are pushed off and perish like leaves a bulb (the onion, 2), a scape (Dodecatheosn, 3), a culbn by buds containing the rudiments of the rootlets to be (Asunldo, 4), or as a woody column (the oak, 5). evolved next season of growt.h. When a trunk bears permanent or perennial branches, Roots have a remarkable tendency to grow down- the plant is termed a tree; when permanent branches wards, or in the direction of the earth's centre, and arise, not from a trunk, but from the root, the plant is from experiments, it seems not unlikely that this ten- termedl a shrub; when small and much branched, a deney is an effect of gravitation. The precise direction, copse-shrub; when furnished with woody branches that however, is very much influenced by the condition of are not permanent, as in the tree mignionette, it is the soil. Both root and rootlets extend as if in quest termed an under-shrub; and when the whole stem is of food, and this will penetrate sideways or obliquely to not woody, -and dies down every year, at least as far great distances. WThen plants are by any means pre- as the crown of the root, the plant is termed an herb; vented from fructifyiug by seeds, they almlost invariably when a trunk is formed of the hardened bases of leaves increase by extending their roots, from distant points of which have withered and fallen, and is not taper, but which new plants will spring up. Roots thus perform all of one thickness, giving off no branches, as in the the functions of steims, and though the two differ in date and cocoa, the plant is termed a paln.; Trunks many respects, yet there are cases where it becomes which increase by successive layers of new wood on the difficult to distinguish between them. Some species outside of the old, as the ash and beech, are termed of palms send clown abrial roots for the purpose of e.oygenous; those which increase by the addition of strengthening their stemls —these shoots partaking of fibrous matter in the centre, as the palms, are styled the character of both stem andl root. The roots sent enzdoyegous; and those forumed by the adhesion of the out by cabbages and cauliflowers from above the collar, leaf-stalks as they spring from the growing-point, as when they are transplanted to a rich soil, are of the the tree-ferns, are said to be acrogenous. same kind. Many herbaceous plants send out roots in Bluds, which have various forms, but are generally a similar manner when they are earthed up; and trees oval or roundish, consist of the young shoots either of which grow in unnxatural situations, as on a wall or leaf, flower, or twig, and proceed from what is called bare rock, send down roots in quest of soil and mois- the axil of a leaf. They are usually iformed either ture, which afterwards take the appearance of stems. early in summer or in autumn, and are so contrived as The maple, the gooseberry, andl some others, may have to preserve from injury the delicate foliated structure their roots converted into stems by reversing the plants, within. The outside is com-:naI burying the tips of the shoots in the earth, so as posed of tough scales, which to leave -the roots in the air. Ins this case the branches are frequently covered with will soon send out fibrous roots from the joints which a gumnmy resin; and. they have been buriedl in the earth, and the -fibrous part of are internally kept warm the old roots withering, the roots themselves will gra- by a downy substance interdually assume the character of branches. posed between the leaves.'e Tlie Sltei oer Stlk. —When a plant shows itself above To this envelope (e e e) Linthe ground, it evidently manifests a strong tendency to nillus applied the term hythe light. Light, in fact, is essential in bringing it to bessnauzzlsum, because it serves maturity, and in giving the green colour to its leaves. for the winter protection of' The steln, with a few exceptions, is always above the young and tender porgronnl, and is furnished with joints or nodes at regular tions of the bud. The inner listances, where the fibres and vessels take a curved scales perform the functions direction, so as to form a little recess,.plainly dis- of leaves, until these are perfected and fully expanded, cernible wvhen the branch is split in two, in the centre when they drop off; but in some trees, as in the apple of which the bud is formed that afterwards expands and the almond, they are converted into leaves; whilst into a branch furnishedc with leaves, and sometires in others, as the rose, they are converted into the petioles producing flowers and fruit.' The stem,' says Rennie, or foot-stalks of the real leaves, which spring out of is divided from the root by the part called the cro-wI1 them. T When the central part of a bud contains leaves or collar. The space between the collar and the first only, it lengthens upwards as it expands into a branch; leaf or bud is termed the bole; but the great body of a thus a leaf-bud and a branch-bud may be said to be stem is called the trunk. The stem of grasses, corn, andl the same. When it contains a flower, this is situated reeds, is termedl the straw; the stem of palms, ferns, as in -the bulb of tlhe tulip, in which small bulbs are mushroom s, and sea-weeds, is termed the stalk; the formed on the edges of the crown of the root between 72 VEGETABLE PHYSIOLOGY. the scales, which gradually enlarge at the expense of With regard to the manner in which leaves project the scales, are detached, become perfect bulbs, and send from the branches, and their distribution over the up leaves and flower-stalks. With respect to the man- woody cylinder to which they are attached, every posner in which the leaves are folded in the bud-they sible variety may be observed. They may be oppositemay be plaited, as in the palm and birch; doubled, that is, two leaves growing onl either side of the branch, as in the rose and oak; embracing, as in the iris and the one directly opposite to the other; alternate, when the sage; double embracing, as in valerian, teasel, &c.; one leaf springs out on one side of the branch, and andouble compound, as in the carrot, mimosa, &c.; rolled other on the opposite side a little above it, and so on; inwards, as in grasses; tiled, as in privet, lilac, &c.; whorled, or vesticillate, when a number of leaves grow rolled outwards, as in'rosemary, primrose, &c.; rolled round the stemn from a common knot or joint, as in lengthways, breadthways, rolled from the tip to the the bed straw. The distribution of alternate and opbase, or wrapped round the stalk. posite, however, is not regular; for in some instances The buds of trees being in a state of great sensibility, it will be found that the leaves on the lower part of and feeling the first warmth of the sun, the vitality of the stenm are alternate, whilst those on the upper are the continued shoot is roused into action; it attracts opposite. the moisture contained in the neighbouring cells There is a numerous description of plants which charged with nourishing matter; the rising sap also have few or no leaves, as the torch and melon thistles; enters its vessels; it gradually swells, and bursting the but their stems are much dilated, presenting a large enclosing scales, pushes into the light and air, unfold- superficies of parenchymous exterior to the air and ing its leaves successively as it advances, until the light; or they are profusely covered with spines, which whole tree becomes green. no doubt, conjointly, do the office of leaves. It may Leavcs.-Leaves are the grand ornament of plants, be remarked that such plants as the common garden and from their numbers, position, and delicacy of orga- rhubarb, which require much moisture, are provided nisation, they are designed to effect an important office with very broad leaves, which catch the rain that falls in the vegetable economy. Springing from the branches, upon them, and also, by their umbrageous quality, and exposed in profusion to the atmosphere, they per- preserve the soil from being parched. form the functions of a breathing apparatus analogous Green is the most general colour of leaves, but some to that of the lungs or gills of animals. A similar are red, or purple, or yellow; some appear nearly purpose at least is designed; for the circulatory sap white, in consequence of being clothed with short woolly of plants, like the blood of animals, requires to be ex- or silky hair. They differ much in substance and posed to the atnmospheric influence, in order that it structure: some are ismmensely thick and fleshy, as may be suitable for nutrition. This purpose is accoml- those of the genus aloe; others remarkably thin, as plished by the agency of the leaves, to which the sap, those of the beech. The texture of the surface is also on rising from the roots through the stem and branches, very dissimilar: some are rough, prickly, and wrinkled; is propelled or attracted, and there both air and light others smooth and glossy. WXVhatever be their form or exercise their beneficial influences. Leaves are thus appearance, it is found, by minute microscopic obserindispensable to the growth of plants, and care should vation, that the interior of the fine membranous subbe taken not to injure them; for defoliation, either stance consists of cells and passages suitable to the due naturally or by art or accident, instantly arrests the exposure of the sap, the inhaling of air, and the absorpgrowth, and the failure or diminished expansion of tion of humidity from the atmosphere. foliage is a certain sign of debility. A leaf consists generally of two parts-the petiole, ORCGAS OF REPRODUCTION. or leaf-stalk; and the laminia, or that part which is The organs of reproduction are the flowers, fruit, and broad and thin. Sometimes, however, as in the rose seed; and these, or some modification of them, nmlst tribe, stipules (s s) are attached to the base of the petiole. exist in every perfect Phanerogamous or flowering plant. The leaf-stalk (a) is that part which connects the leaf Flower-buds are produced like leaf-buds, from which they differ chiefly in containing one or more incipient flowers within the leaves; the flowers being wrapped up in their own floral leaves, or bracts, within the ordi-.XX %',i ^ nary leaves, which have their usual outer covering of scales. The growing point is generally developed when the leaves expand, but it is short and stunted, and un___ W W@&&S & h like the branches produced from the leaf-buds. Every flower-bud, as soon as formed in the axil of the old N A SH> /t g Jleaf, contains within itself all the rudiments of the future flowers. If a bud be gathered from a lilac or a // /.;I ~ Xhorse-chestnut very early in spring, all the rudiments of the future leaves and flowers will be found within db 8 kiR~s S it, though the bud itself may not be more than half an inch long, and the flowers not bigger than the points of the smallest pins. Floc lers.-A flower consists of several distinct partsthe calyx, corolla, stamens, disk, nectarium, pistillulm, withll the branch, and at the base will be found slightly and receptacle. A flower is essentially constituted by hollowed, in which a bud rests. Sometimes the leaf- the presence of sexual organs, either male or female. stalk is wanting, as in the sow-thistle and catch-fly, WVhen there is only one of these present, the plant is and in this case the leaf is said to be sessile, or sitting. termed unisexual; but more commonly these organs The lamina, or broad part of the leaf (b), is frequently are both present in the same flower, which is in this of a different colour on the under side to what it is on case ternied a hermaphrodite. In some instances, althe upper. This is exemplified in the common silver- though the same plant bears both male and female weed (Potentilla anserinc), the leaves of which are organs, it is not hermaphrodite, as these organs occur hoary on the lower side and green on the upper. in different flowers; in others, again, the male and Leaves are either cachdcozus, falling in summer; deci- female flowers exist only in different plants. Lastly, du.ozrs, falling in autumn; persistent, remaining till male, female, and hermaphrodite flowers are sometimes pushed off in the following spring; or peremnial, when found mingled together, either on the same or on difof still longer duration, as in evergreens. The forms of ferent footstalks. Sometimes the male or female organs leaves are exceedingly varied-being simzjle or com- alone, protected in a small scale, constitute the flower; pon1d; and these again are distinguished as oval, but in general they are surrounded and protected by lanceolate, hastate, sagittate, pinnate, cordate, &c. the corolla and calyx. All these are commonly borne 73 CHAMBERS'S INFORMATION FOR THE PEOPLE. on a stalk called the peduncle (from pes, pedis, a foot), tion they may be opposed to the divisions of the petals, which, expanding at its extremity, forms the receptacle, or they may alternate with them. Sometimes they or torus, as it has been called, upon which the whole protrude beyond the corolla, at other times they are wholly included within it. Their direction may be DoRX herect, pendant, or horizontal, and their summit is variously inclined to or reflected from the centre of the flower. The filament which supports the anther is most I' \\\\.1commonly straight and filiform; sometimes, however, it is otherwise. It varies from being as small as a hair; to be large and flat like a petal, and its summit is either dSHW~~~~~ Da ofpointed or obtuse. On the summit is that essential part the anther, which is generally formed of two small I(2! membranous sacs, attached immlediately to each other, or united by an intermediate connecting body. In form, anthers are subject to great variety, and, like the filaments, they sometimes cohere so as to form a sort of tube. Their colour is often yellow, orange, violet, white, a a, stamens; d, filament; b, stigma, or summit of pistil; e, &c. but never green or truly blue. style; c, ovary, or seed-vessel; f, peduncle; g, calyx; h, corolla. The pollen contained in the anthers consists of numeThe pollen contained in the anthers consists of numeof the parts above mentioned are supported. What is rous regularly-figured small particles, which possess in called the berry in strawberries appears to be nothing different plants a very different figure, size, and colour. more than the receptacle bearing the naked seeds on The number of particles in a cell, which is very small, its surface. It is called common when a number of sometimes amounts to many thousands. In some florets rest on one receptacle. The round button which flowers the pollen consists of transparent grains; in is exposed when the downy seeds are blown from the others they are of a white, purple, blue, or brown, and head of the dandelion, is an instance of the common more frequently of a yellow colour. When a grain of receptacle. pollen is dropped into water, it swells and bursts, and The calyx is the external leafy envelop surrounding a minute quantity of matter escapes, which is supposed the flower, and in which it rests as in a cup. Some- to be the fecundating principle of times it is entire, but more frequently it is divided into the pollen. We may illustrate b segments (sepals), which are more or less separated the action of the pollen from the i from each other. It is most commonly green, but in anthers, by referring to the ansome flowers it is highly coloured, and with difficulty nexed engraving, in which a is the to be distinguished from the corolla. filament or stalk of the stamen, The corolla is the true flower or blossom, and con- b the anther on its summit, and sists of several divisions or leafy parts, called petals, c the pollen or dust in the act of which are almost all articulated at the base, and con- being shaken down upon the stigsequently fall off at the earliest manifestations of ma- ma or upper part of a pistil, of turity or decay. The extensive variety of tints in the which we observe three in a group. flowering part of plants is a remarkable circumstance In this figure it may be remarked that the anther is in vegetable economy; and what may be the precise a roundish-shaped body, delicately poised on the filause of such gaiety of colour, has formed the subject of ment, and ready to vibrate and impart its dust to obhphilosophic inquiry. Independently of the exceeding jects beneath or near it. beauty to the eye, which is certainly a matter for pleas- The pistil is a kind of tube with a communication ing gratulation, it is believed that the lively colours from the stigma, through its style or stalk, to the ovary are useful in attracting insects-these creatures inci- or seed-bag beneath, and down this the pollen is perdentally performing an office in the reproductive eco- mitted to exercise its influence. The seed organ or nony, and in carrying off saccharine exudations. ovary occupies almost always the inferior part of the The lower part of the single petal of a corolla is pistil, and it is there that the process of fructification called the claw, corresponding to the stalk of the leaf; is fully developed. When cut open, it exhibits one or and the broad part is called the limb. The corolla is more cavities or cells, in which are contained the rudifrequently furnished with certain appendages, attached ments of the seeds or ovula; and it is in it that the either to the throat or to the base of the petals, called change of the ovula into perfect seeds is effected. It is nectaries. These are placed in different parts of the of various forms, but most commonly ovoidal. It is corolla: in the common auricula they surround the edge generally seated upon the receptacle together with the of the throat; in the ranunculus or buttercup tribe, stamens, but frequently it is placed below the flower. they appear like scales at the bottom of the claw; and It may be remarked that the pistils spring from a in the monkshood, in the form of a spur behind the nectary or disk in the centre of the flower, and are corolla. They receive the name of nectaries from the surrounded by the stamens. supposition that they secrete honey, and they are al- The precise mode of fructification is by no means ways found to contain a clear, sweet-tasted fluid. clearly ascertained. The stigmata are in all cases moistStamens, &c.-Within the beautiful corolla are ob- ened with a clammy fluid, which causes the pollen-cells served several small filamentous objects, on some of to swell, burst, and discharge their minute granules. which are particles of fine coloured matter like dust. Some suppose that these are taken up by spongelets in These are parts of the reproductive organisation, and the summit similar to those of the root, while others consist of stamens and pistils. In general, a stamen allege that the fluid matter in which the granules float consists of two parts, in most cases of a filament (from is sucked up. It has been discovered that the grains filum, a thread), which is usually white, and always of of pollen, when shed on the summit, in a few hours an anther, which is generally yellow or purple. It has shoot out one or more delicate tubes, which by some been shown that the stamens are always next to the physiologists are supposed to extend down as far as the petals-that is, between their base and the base of the seed-organs, and to expand around and between thq seed organ. It is upon the number and arrangement nascent seeds. Some believe them to convey thither of the stamens that systematic botanical arrangements the granules, which at least enter into the tubes; have principally been founded. The following are a others, however, deny that this is the case. The seedfew characteristics of the number, length, position, di- organ lies at the base of the pistil, and contains the rection, &c. of the stamens. The number of stamens in seeds, either nascent or advanced to maturity. It bears each flower varies from one to twenty, or more. In a very strong resemblance to the egg-organ of birds length they are equal or unequal, and this dispropor- and insects, and its parts have accordingly received tion is sometimes symmetrical, sometimes not. In posi- from naturalists the same scientific names. The seed74 VEGETABLE PHYSIOLOGY. organ is usually of an egg-oblong form, and is always their dispersion. In some species the sorn are situated composed of an outer membrane, a middle membrane, merely under the epidermis of the leaf, forming little and an inner membrane, all intimately united. As protuberances, which, on the slightest rupture, discharge every seed derives its nourishment from the inner mem- their contents,'to be scattered abroad by every breeze brane, there must be a communicating point; and this that blows. As an order, ferns are very widely dispoint being always on the verge of the membranes may tributed, generally consisting of a number of leaf-like be so termed; that on the seed being termed the seedscar, but popularly, though improperly, named the eye. In some species the verge bears a number of smaller Hi ~' verges, to each of which a seed is attached by means of the funicle or seed-stalk. All these parts are obvious in an unripe pea or bean. d Seed-vessels are various in form-as, for example, in the case of the pea (a) the vessel is a legume, or pod; in the apple (6) it is the body of the fruit, or pome; and in the filbert it is a nut. Ferns, showing the Soar on the back of the Fronds. members calledfsonds, attached by tough fibrous petioles to a subterranean stem-the fronds being the only visible portion of the plant. In some varieties, however, the stem rises above ground to the height of thirty ~F~IB a. s icd L. or forty feet, forming the well-known tree-ferns of New All fruits, in reality, are but so many vessels, or re- Zealand and Van Diemen's Land. In the eqsuisetumzs, ceptacles for the seeds; and the various forms in which or horse-tails of our marshes and ditches, the capsules they appear are individually suitable to the purposes which contain the spores are placed on the points of of their growth. The seed contains the embryo or germ bracceated spikes, arranged in rings round the stems. of the future plant, which is generally surrounded by Each spore is furnished with an elastic filament, which a nutritious substance termed the albumen, destined is at first coiled around it, but which, in its endeavour for the support of the young plant before its organs are to uncoil, makes the sporules jerk and leap as if they sufficiently matured to allow of its supporting itself. were alive. The horse-tails are herbaceous perennial In most instances the albumen surrounds the embryo; plants, having hollow striated stems, these being either but sometimes it forms part of the cotyledons or seed- simple or branched. In point of size they are now inlobes, and at others it is wanting altogether. Even significant members of the vegetable kingdom; but where it exists, it varies very much in quantity, some- geology has revealed the gigantic proportions they bore times being much smaller than the embryo, while in in ages long past, when, instead of slender stems of a other cases, as in the cocoa-nut, it weighs as many, or foot or two high, they reared their gigantic pillar-like more ounces, than the embryo does grains. The albu- trunks to a height of twdnty or thirty feet. The sporules men varies in quality as much as it does in quantity. of the pillworts (nassiIt is generally fleshy, as in the pea and bean; but leacece) are enclosed in sometimes it is farinaceous or floury, as ii the wheat, little bcall-like recep- and in the marvel of Peru; at other times it is oily, as tacles at the bases of in linseed; horny, as in the coffee; or even stony, as the leaves (see fig.); in the kind of palm whose seed forms the substance the club-mosses (lycopocalled vegetable ivory. In the nutmeg and the custard liacece) have little coneapple tribes it appears to be perforated in every direc- like spikes at the tips:ttion by a mass of dry cellular tissue. of their branches, un- If the embryo consist of one seed-lobe or cotyledon, der the scales of which Pillwort. as the cocoa, it is said to be mzonocotyledonous; if of lurk the reproductive two, as in the beech and oak, dicotyledoznous-and these embryos; and in the true mosses (mssci) the spores are terms are generally used indiscriminately for exoge- enclosed in urn-shaped capsules, which stand out from nous and endogenous; while cryptogamous or flowerless the leaves on slender hair-like stalks. In the liverplants, from being propagated by sporules instead of worts and lichens there is a somewhat similar proviseed, are said to be acotyledonoaus-that is, without any sion; and in the stoneworts and alga (sea-weeds), which cotyledon whatever. This distinction of the seed-lobe are aquatic, the sporules are enclosed in the substance is fixed and enduring throughout the whole cycle of of the plants. vegetable growth-making its appearance, as will be The fussgi, or mushroom tribe, which constitute more fully shown under SYSTEMATIC BOTANY, in the the lowest forms of vegetable development, are exstructure of the stem, or trunk, in the leaves, the tremely diversified in their size, shape, colour, and flowers, and the fruit. consistence. They are entirely composed of cellular Fructi catione offiowerless planets.-As already stated, tissue, and some are even apparently animated; so that the lowest forms in which vegetables make their ap- they are regarded as connecting links between the vegetpearance are those of the* c'yptogamouzs, or flowerless able and animal kingdoms. The common field-musihorders-such as the ferns, lichens, mosses, sea-weeds, room is one of the best known, and forms the type of and fungi. In these the manner of fructification is the family; but the mould on cheese, stale bread, the very remarkable, and quite different from that of mildew on trees, the rust on corn, and many other flowering plants. They have neither flowers nor seeds, minute and yet unobserved appearances of a similar but are propagated by little embryo plants, called nature, are all fungi. They have no fronds or leaves, spores or sporules. and are hence termed aplyllozus. Their organs of reproIn the ferns (filices), which are the largest and most duction consist of sporules, lying loose on the tissue of highly-organised of the flowerless orders, little brown the plant, or collected in certain places, which are disspots, called sosi, may be seen on the under sides of the tended by their aggregation. leaves or fronds (see fig). Each of these is composed But though the botanist can thus detect, by the aid of a number of minute membranous capsules (thecce), of the microscope, the embryos of flowerless plants, aid which contain the reproductive sporules, and which are can describe their situation and appearance, he underoften furnished with elastic apparatus for assisting inll stands as yet but little of the manner in which these 75 CIHAMBERS'S INFORMATION FOR THE PEOPLE. reproductive organs perform their functions.'WVe are Another great object which nature has in view by entirely ignorant,' says Professor Lindley,'of the the germination and dispersal of the algae, mosses, and manner in which the stems of those that are arbores- lichens, is clearly that of preparing the way for a higher cent are developed, and of the course taken by their order of vegetation. It cannot possibly escape our ascending and descending sap-if indeed in them observation that the tendency to vegetate is a power there really exist currents similar to those of flowerinog restless and perpetual. We hew a stone firom the plants; which may be doubted. We know not in what quarry, and place it in a damp situation, on the ground way the fertilising principle is communicated to the or in a wall, it is all the same which, and shortly a sporules or reproductive grains; the use of the different green hue begins to creep over it. This is the conmlinds of reproductive nmatter found in most tribes is mencement of a vegetable growth, produced by germs entirely concealed from us. It is even suspected that floated in the atmosphere; and being attached at ransome of the simplest forms (of alge and fungi at least) dom to the stone, have been brought to life through are the creatures of spontaneous growth; and, in fine, the agency of the moisture. Other stones equally we seem to have discovered little that is positive about exposed, but in dry situations, have also received a the vital functions of those plants, except that they clothing of these germs, but circumstances not being are reproduced by their sporules, which differ fron suitable, they have not been developed: give the mnoisseeds, in germinating from any part of their surface, ture, and they will immediately appear. We hew instead of from two invariable points.' another stone from the quarry, and build it into the zFunctions of flowerless plants.- Insignificant and pier of a bridge, just within the surface of the water: lowly as the cryptogamia may appear to the eye of the shortly, the same kind of green algae will appear; but physiologist, they are nevertheless important auxiliaries the wet being in greater abundance, and more contiin the operations of nature. It is true that man and nuous, the growth will become mbre luxuriant. Inhis works may suffer from the ravages of fungus growth, stead of the simple green ooze, we have the addition of that mildew, rust in corn, moulds, and other micro- long filaments resembling hairs (cosfervce), which float scopic vegetation, by their rapid increase and destrue- and accommodate themselves to the water around. tive effects on the substances from which they spring, The inquiry may perhaps here be made-supposing nmay cause incalculable damage; but this very scourge that nature designs this species of growth to be a foreprovides an incentive to intelligent prevention and runner of a higher order of vegetation, how is that care, while in creation there are no more useful sea- result to be brought about? To answer this, we must vengers of decaying matter than the parasitic fungi. take an expansive view of the subject, and not confine In a dry season, for example, and on a favourable soil, ourselves mlerely to one dclepartment of science. Nature rust rarely makes its appearance: certain conditions are is incessantly working out vast ends by hunmble and necessary for its developument; and it is to obviating scarcely recognisable means. It seems to be a principle these that the farmer must look for exemption from that nothing shall remain stationary or unchanged. this destructive malady in his crops. It is now placed The whole surface of our planet is every instant alterbeyond a doubt that it arises in many cases from the ing in its features: mountains are being washed down over-muanuring of fields; the grain is overloaded with into the plains, rocks are mouldering into soil, the sea nourishment, and the dormant fungi, brought into a is filling up at one place and encroaching onl the land condition of development, speedily show their destruc- at another, and water-courses are constantly shifting tive properties. The tendency to rust may be neu- their outlines. The duty of filling up seas, ponds, lakes, tralised by steeping the seeds before sowing in a corro- and rivers, is consigned to divers means within the sive solution, or strong brine; but the same end may be aninmal and vegetable economy; and one of these is better secured by not over-manuring, or by a free use the growth of algae and other aquatic plants. Take a of saline manures. Again, most of the fungi existing pond of water, and shut off its means of supply from only by the absorption of fetid exhalations, and rapidly rivulets and springs, and then observe what an effort depriving them of their insalubrious properties, execute nature will make to fill it up. The sides and bottom duties analogous to those of certain tribes of insects become speedily covered with a luxuriant crop of con(maggot-flies, for instance), and in this respect-have fervni; other plants, which grow only in water, begin been appropriately associated with these aninmals as to mnake their appearance, their seeds being wafted tife' scavengers of nature.' thither by winds; at length the superficial matting of It will now be understood that mould is a fungous herbage is able to support the weight of birds; grass vegetation, produced by a previous deposit of germs in grows; there is alternate vegetation and decay; finally, the tissue or on the surface of the object on which it the pond is filled up, and a forest of the highest order grows. The proximate cause of its development is ge- of trees may in time cover the site of the original nerally damp, and without this condition, the embryo humble confervu. What, indeed, are the extensive remains in a dormant state. Still, it may be asked peat-msosses but lakes and pools choked with vegethow cheese happens to have green mould at its very able matter, which remains in a half-consumed centre: the reply is, that the fungous germs floating in condition. Thus we see that the green hair-like ooze the atmosphere had various opportunities of finding which grows upon stones in the water, humble and Cadmission into this article of diet. They may have apparently insignificant as it is, performs a distinct been deposited on the grass of a field; the grass was part in creation necessary to work out the importamt eaten by the cow, and the germs were so lodged in the designs of Providence. milk; or, what is nimoe probableS the germs fell upon the curd, and there lay concealed till a certain damp- PIIHENOENA OF VEGETATIO>:. ness in the cheese brought their vegetative powers into In addition to the ordinary functions of the organs, operation. It is well known that the exposure of curd which are the same in all plants of the same genus, for a day to the atmosphere will have the effect of there are certain anomalous functions which cannot be producing cheese liable to mould. A fully more sur- reduced to regular laws, and which differ in different prising instance of fungous vegetation in a secluded species even of the same genus. The most remrarkable situation, is that which occurs in the fermenting of of these are the occasional i)ritability of plants, their yeast and other substances. Fermentation is, in one colours, fragsansce, and tastes. respect, a chemical process, forming a first step towards Iritability. - The irritability of animals depends dissolution; but the action is also vegetative. The entirely oil their nervous system; but as plants have whole mass of matter gradually assumes the condition no nervous system, their irritability is more difficult of active vegetative growth. The fungous germs which to be accounted for. Dr Darwin indeed asserts that had been incorporated in the material begin to live plants are only an inferior kind of animal, and that amnd expand, each being a plant which grows and gives they, or at least some of themn, have a brain and a rise to new plants of the same species, until the entire stomach, and are endowed with the lower senses. Acfermestling principle is exhausted. cordcing to this fanciful doctrine, the medulla, or pith, VEGETABLE PHYSIOLOGY. was made the seat of sensation, and was considered ana- gether, till the body of the insect has wasted away. logous to the spinal marrow of animals. The doctor, This apparatus being the nearest approach to a stohowever, had no followers, as his hypothesis presented mach which has been yet observed in plants, an extoo many difficulties to be even partially believed. The periment was tried some years ago of feeding a dionra principal phenomena of vegetable irritability may be with very small particles of raw meat, when it was divided into three kilds-namely, those caused by found that the leaves closed in the same way as atmospheric influence, thoqc depending upon the touch they would have done over an insect, and did not open of other bodies, and those which appear to be perfectly again till the meat was consumed. Saracenia, or sidespontaneous. Atmospheric influence occasions the saddle flower, the leaves of which have a pitcher-shaped closing of the leaves over the extreme point of the petiole (b), also decomposes flies and other insects young shoot at night, as may be observed in the chick- caught in the pitcher-a peculiarity which seems to weed and several other common plants. The folding belong to all plants having pitcher-shaped leaves. of some floweis in the absence of the sun, and the open- The spontaieouts movenzents of plants are much more ing of others as soon as that luminary has withdrawn dificult to be accounted for than those occasioned by its beams, are ascribable to a similar cause. The white atmospheric phenomena or by external touch. It is marigold closes its flowers on the approach of rain, and true that the leaves elongate, the flowers expand, the the dwarf celandine folds up its bright crimson corolla anthers burst, and the seed-vessels open spontaneously; about four o'clock every afternoon. The evening prim- but these are movements caused by the progressive derose, on the contrary, will not open its large yellow velopment of the plant, and subjected to regular laws. flowers till the sun has sunk below the horizon; and The spontaneous movements which arise from irritathe night-blowing cereus only expands its magnificent bility are quite different-as, for examnple, those of the blossoms about midnight. Some flowers are so regular leaves of lIedysar'umv gym'ans. This plant has compound in their hours of opening and shutting, that Linnmeus leaves, the terminal leaflet of which never moves, except formedl what he called Flora's Time-piece, in which to fold itself close down to its own stalk; but the side each hour was represented by the flower which opened leaflets have such eccentric movements, as to render it or closed at that particular time. Solar light is the difficult, if not impossible, to explain them, and which principal agent in producing these phenomena; but might appear, indeed, to a fanciful mind as though the in some cases flowers have been known to open by whole plant were actuated by a feeling of caprice. Geneartificial light. Decandolle found blossoms expand rally, all the leaflets twist and whirl themselves about beneath a lamp nearly as well as beneath the sun itself; in an extraordinary manner, though the air of the house and the crocus-flower, which closes at night, has been in which they grow is perfectly still; but frequently the known to expand as wide as possible when gently ex- leaflets on only one side will be affected, and someposed to the light and heat of a fire. One of the most times only a single leaflet will move, or all will become renmarkable circumstances respecting the effect of atmo- motionless together; and when this is the case, it is spheric influences is, that the same causes do not affect quite in vain to attempt to set them again in motion all plants, and yet no peculiarity of construction has by touching them; though sometimes in a moment, as been discovered in those that are so affected to distin- if from the pure love of mischief, after the touching guish them from those that are not. has ceased, the leaflets will begin to move again as The irritability produced by external touch is a rapidly as before. In the like manner the side leaflets familiar but little understood phenomenon. The move- frequently continue their eccentric movements all mlents of the sensitive plant are well known; and it is night, while the terminal leaflet remains quietly folded also known that if the ripe seed-vessels of the noli-me- up, anld apparently fast asleep. Cold water poured tangere be touched in the slightest manner, they will upon this plant stops the motion of the leaves, but it open with elasticity, and scatter their contents. In is renewed as soon as the heat of the stove in which the same manner the fruit of the squirting cucumber the plant grows has converted the water into vapour. throws out its seeds, and the moist pulp in which they Movell ents analogous to those of the hedysaruml and are contained, with great violence, and to a consider- other foreign plants have been detected by M. Dutrochet able distance. The stamens of the barberry, when in several common vegetables, as the garden pea and touched with a pin, spring forward, and appear to cucumber; and he attributes them to an interior and make a bow to the stigma, after which they return to vital excitation, and not at all to the action of light, their proper position; while the column of the styli- which is opposed to, and, if vivid, arrests them. dium, which includles tihe style and stamens, and which Plants may be deprived of their irritability by keepgenerally hangs on one side, when touched, springs ing them without water, when they become flaccid; or with a jerk to the other side of the flower. The by watering them with a poisonous liquid, in which msost remarkable instance of irritability by contact case they lose not only their irritability, but their lives. is that exhibited by Venus's fly-trap, Dionean nuzs- Life, indeed, appears to be intimately connected with cipula, a native of Canada, but now common in irritability, as the latter quality exists only in plants British conservatories. Its flowers have nothing re- in a vigorous and healthy condition. The functions of mnarkable about them, except that their petals roll up vitality and irritability may be merely suspended withwhen they are about to out destroying life by administering to them the sanse decay; but the leaves are substances-opium, vapour of ether, &c.-which provery curiously constructed. duce stupor in animals. They have broad leaf-like / Color.m —The colour of plants generally depends on petioles, at whose extre- the presence of a substance called chronmule, which is mity are two fleshy lobles, deposited in minute granules in the vesicles of the which form the real leafi, VTf cellular tissue. This substance consists of pure carbon, and which are armed with',) Y'7'li which has been fixed, as physiologists term it, by the strong sharp spines, three /.tl decomposition of the carbonic acid gas absorbed by the on the blade of each lobe, s/ i plant; the oxygen escaping again into the atmosphere, anrid a frinue of longer / while the carbon is permanently assimilated. Both spines round the margin the absorption and decomposition of carbonic acid take (a). When an insect place most effectively under the influence of solar touches the base of the / light; hence plants grown in darkness become etiolated, central spines, the leaf col- or blanched. The chromule in all plants being the lapses, and the poor insect a, Leaf of Venus's Fly-trap; same, it is difficult to explain why leaves should be is caught; being either b, Leaf of Saracenia. green, and flowers of so many varied hues; indeed the impaled by the central spines, or entrapped by the cause is as yet lbut very imperfectly understood. It is others. The leaf then remains closed, the fringe of found, however, that when the leaves first expand, and long spines being firmly interlaced and locked to- are of the brightest green, the grains of chromule are 77 CHAMBERS'S INFORMATION FOR THE PEOPLE. always surrounded by a thin film of gluten, the prin- by decaying animal and vegetable substances, as they cipal ingredient in which is nitrogen. In autumn, the evidently proceed from the volatile parts being liberated gluten and carbon generally have both disappeared, by decomposition. The fragrance of flowers, however, particularly in plants which contain a notable amount escapes while the plants are in a living state, and that of acid, the basis of which is oxygen. In proportion as imost abundantly when they are in vigorous and healthy the oxygen predominates, the leaves become red; hence condition. Besides the flowers, other parts of living the beautiful tints of red and crimson taken by solme plants frequently exhale fragrant odours-such as the leaves in autumn. When the carbon disappears without leaves of the myrtle and geranium, and the wood and the nitrogen, as is frequently the case, the leaves become bark of pines. All these odours proceed from oily or yellow in autumn. It has been observed that the leaves resinous matters contained in the receptacles of secreof plants always turn yellow, red, crimson, or violet, tion; but the laws which regulate their liberation, and and never blue; and this corresponds with the above define their physiological uses, are as yet imperfectly theory, as the carbon, which is dark, is carried out of known. Some botanists consider them to be part of the leaves by the descending sap, and its place partially the excrementitious matter which is thrown off by supplied by oxygen. Thus red, which is the colour plants when it is no longer necessary to their growth; produced by oxygen, predominates in decaying leaves; but if this were the case, the exhalation would continue and violet, which implies a mixture of carbon, is only the same during the whole period of growth, and not found in the dying leaves of the American white oak. vary, as it does, at different seasons, and according to The lime, and other trees which abound in mucilage, the state of the weather. It is well known that plants or gluten, further corroborate this theory, in having are most fragrant in damp weather; and some botanists their decaying leaves yellow. In all cases the colour- have attempted to account for this by supposing that ing matter is not in the sap, which is either colourless, the tissue being relaxed at such seasons, the stomata, or tinged faintly with yellow, but in the cellular tissue; or pores, open wider than at other times, and thus perand thus, while the stem consists chiefly of cellular mit the escape of a greater quantity of the fluid. Trintissue, it is as green as the leaves. chinetti thinks that the use of the odours of flowers is The colours of flowers are more difficult to be ac- to ward off vapour, which might prevent the diffusion counted for than those of leaves, as they are evidently of the pollen; and it is thus that he accounts for the influenced by the soil in which the plants are grown more increase of the odour by damp. This explanation than by solar light. Mineral substances, particularly appears plausible; but neither it nor any of the others iron and manganese, are found abundantly in white which have been suggested will explain why the petals flowers when burned; and it is known that many a of roses, and other flowers, retain their fragrance when common British weed, particularly the herb' Robert,' dried. The use of fragrance in leaves, bark, and wood, varies from a dark rose colour to almost white, accord- is apparently to preserve them from the attacks of ing to the soil in which it grows. Flowers grown in insects; as we find that the smell of the red and Berthe shade are, however, seldom different in colour from muda cedars, of which pencils are made, and of camthose fully exposed to the air and light. The petals of phor (also a vegetable product), are sufficient to keep the common buttercup and the lesser celandine are of the moth from attacking substances with which these as brilliant a yellow in town gardens enveloped in the are in contact. smoke of London as on any country hill; and roses The odours of plants are of three kinds-permanent, always maintain their brilliant tints, even when the fugitive, and intermittent. Permanent odours are bushes on which they are produced are evidently (lying those given out slowly by the plant, not only whilst it for want of a clear atmosphere. Flowers may be made is living, but also after the fragrant part has been to change their colours by the influence of the soil in a separated from the root, though it be not in a state of most remarkable manner. The petals of the common decay. Of this kind are the odours of fragrant wood, hydrangea, which are naturally pink, may be made of the dried petals of roses, and some other flowers. blue by planting the shrub in soil impregnated with In these cases the receptacles of secretion are generally iron. The change produced in tulips, carnations, heart- buried cl-so deeply in the tissue, that the essential oil eases, &c. is still more extraordinary. The flower of a with which they are filled canl only escape slowly, and seedling tulip is generally of a dull brownish crimson; in very small quantities. In some cases, indeed, the and after remaining of this colour two or three seasons, receptacles of secretion are so deeply seated, that the it will suddenly break, as the florists term it, into the wood to which they belong appears devoid of scent, till most brilliant and varied tints of rose, white, yellow, its essential oil is volatilised by exposure to heat. brown, or purple, without leaving any trace of the Fugitive odours arise from essential oils contained in original colour. To produce this change, florists try a receptacles just below the epidermis; and when there variety of means, all of which have relation to the soil; is only a minlute quantity of oil in each cavity, the for example, they sometimes keep their tulips in poor duration of the fragrance is correspondingly short. soil, and then suddenly transplant them into one ex- Intermittent odours are the nIost difficult to be acceedingly rich; or they reverse the process: at other counted for by the vegetable physiologist. It is only times they change them suddenly from a sandy to a known that the night-smelling stock, the Indian jasclayey soil. As a further proof that light is not the amine, and several other plants, which are entirely sole cause of colour in plants, it is well known that devoid; of scent during the day, are delightfully fraferns and mosses have been found green in mines where grant during the night. One of the orchideous plants they have grown in total darkness; and green and red produces its powerful aromatic scent only when exposed sea-weeds of the most brilliant tints are frequently to the direct rays of the sun; and the flower of the washed up from the bottom of the sea, where the light, night-blowing cereus is fragrant only at intervals of being weakened by passing through such an immense about half an hour during the time of its expansion, body of water, can have but little colouring effect. preserving the same kind of intermittence even when The colouring matter extracted from vegetables is separated from the stenm. of great economical value, being extensively used in Tastes. —The tastes produced by vegetable substances the art of dyeing. Some of these dyes are the same are generally recognised as sweet, acid, bitter, astrinwith the natural colour of the parts from which they gent, austere, or acrid. The juice of the sugar-cane, are derived; such as saffron, which is the yellow stigma for example, is sweet, that of an unripe apple acid, the of a species of crocus; but others, as woad and indigo, aloe bitter, the leaf of the bramble astringent, and the are totally dissimilar, being blue or black, when the cranberry austere. It has been already stated that native vegetable texture is green! the ascending sap is at first insipid, and that it graFteyrarnce.-The cause of fragrance in flowers has dually acquires the peculiar taste of the plant; but it never yet been fully explained. We know that all is only in the descending juice that the taste-yielding organised bodies consist partly of volatile matters, and principle is fully developed. Why the taste of one thus we can readily account for the odours given out vegetable should differ from that of another grown in 78 VEGETABLLE PHYSIOLOGY. the same soil, the physiologist is unable to determine; great rapidity during thundery weather; but this he as yet only understands a few of the causes by which may result from the nitrogenised products of tho tastes may be modified or destroyed. The principal showers which then fall, as well as from the effects of influences which modify the tastes of plants are atmo- electricity. The progressive states of vegetable growth spheric and solar; light, exposure, and warmth being are the result of chemical changes; and as these changes those under which taste, as well as all other qualities are more or less accompanied by electricity, it is supof vegetables, are most fully developed. Every one is posed that plants evolve electricity as well as heat. acquainted with the blanching effects of earthing, as The conversion of water into steam is followed by a exhibited in celery, or in the shoots of the common sensible evolution of electricity; and the evaporation rhubarb. The fruits grown in our own island during a which takes place from the surface of rapidly-growing wet and sunless season are insipid compared with what leaves produces the same phenomenon. The general they are in a dry and bright summer; and the general electric state of plants is said to be negative; and some vegetation of the arctic and temperate regions is less have attempted to connect the luxuriant vegetation of powerful in kind than that of the tropics. Even the the tropics with the thunder-storms of these regions, on successive periods of a day exercise an influence on the the supposition that when the atmosphere is 2oesitively tastes of growing plants, according as they are stimu- electrified, the two opposite states will give rise to such lated by solar light to absorb or exhale oxygen-the commotions. Of late years, attempts have been made principle on which the peculiarities of taste greatly to apply the principle to agriculture; conducting wires depend. As a general law, it may be stated that the have been laid around experimental plots, but with drier and warmer the situation, the more exposed to such varied, and even contradictory results, as to prelight, and the slower the growth of any vegetable, the clude anything like a determinate conclusion. more intense is its peculiar flavour. The physiological uses of the different tastes are as imperfectly under- SECRETIONS OF PLANTS. stood as the causes which produce them. Some of Substances possessed of varied properties are secreted them may be given for the preservation of the vegetable by plants, according to their respective natures, and against the attacks of animals at certain seasons of their healthy or diseased condition at the time of seits growth, whilst others seem as directly bestowed to cretion. Some of these substances are produced by the render plants agreeable to the animals destined to con- ascending sap; but the greater number are deposited sume them. by the elaborated or proper juice, and consequently Lunminosity, Heat, Electricity.- The luminosity of are never secreted during spring or early summer. The plants-that is, the evolution of light either from intensity of those derived from the latter source deliving or dead vegetable structure —is a rare and pends in a great measure upon the influence of solar curious phenomenon. Flowers of an orange colour, as light; hence they are much stronger, and more abunthe marigold and nasturtium, occasionally present a lu- dantly produced, in tropical than in temperate climates. ruinous appearance on still warm evenings; this light Most of them being derived from the true or arterial being either in the form of slight electric-like sparks, sap, they would seem to serve some purpose in the or steadier, like the phosphorescence of the glow-worm. reproduction or nourishment of the plant; but others, Certain fungi, which grow in warm and moist situa- from the manner in which they are deposited or ejected, tions, produce a similar phosphorescence; and decay- appear to be of no utility in the vegetable economy. ing vegetables, like dead animal matter, have been Some of them are excretions as well as secretions; but observed to emit the same kind of luminosity. This whether they are to be considered as essential comphenomenon seems connected with the absorption of ponents of the sap, or evacuations necessary to the oxygen; and the parts emitting it are most luminous healthy condition of the secreting organs, has not yet when immersed in pure oxygen, and cease to emit it been determined. Being exceedingly varied in their prowhen excluded from that element. Luminosity is perties, they are of great utility to man, either as articles sometimes occasioned by actual combustion of the of food, clothing, medicine, ornament, or luxury. volatile oils, which are continually flying off from cer- The economical applications of vegetable secretions tain plants: those of the Dictamnus albus will inflame and excretions are so numerous, that it would be abupon the application of fire. surd, in our limfited space, to enter upon anything like The evolution of heat by living plants is a more details. It is even difficult to attempt any classificacommon phenomenon. We are aware that warm- tion of them; for, though differing in their properties blooded animals have the power of keeping up a certain and external appearance, many of them are identical temperature within them, which varies at certain stages in chemical composition, and, subjected to peculiar of their growth, and perhaps periodically. This result treatment, readily pass into new and similar combiis obtained by respiration-the oxygen of the atmo- nations. Some, for instance, are farinaceous, as barley; sphere uniting with the carbon of their blood, and pro- while others are saccharine, as the juice of the sugarducing a species of combustion. A similar, though less cane; and yet both, when subjected to fermentation, understood phenomenon, seems to take place in the produce similar liquors. Many are oleaginous, balrespiration of plants. In germination heat is sen- samic, or resinous; some are narcotic, aromatic, or sibly evolved: a piece of ice placed on a growing leaf- mucilaginous; while others are astringent, purgative, bud will dissolve, when it would remain unchanged in or poisonous. For examples of these divisions, the the open air; and experiment has proved that the sur- reader has only to recall to mind such substances as face of plants is three or four degrees higher than the palm and olive oil, myrrh, resin, opium, camphor, gumsurrounding medium. Again, the internal temperature arabic, tannin, gamboge, prussic acid, aloes, colocynth, of a large trunk is always higher than the surrounding and a thousand others of every-day familiarity. atmosphere, and though young shoots are sometimes Besides the proper excretions and secretions, there frozen through, the general structure both of the wood are several adventitious substances found in plants, and bark is such as to conduct heat so slowly, that the which are not the products of vital organisation. Lime, internal warmth is never reduced beyond what seems for instance, is found in the ashes of many plants in necessary to the maintenance of vitality. Generally union with acids, and sometimes it is excreted in the speaking, it may be asserted that plants possess.1n form of a thin crust on their leaves. Silica also occurs internal vital temperature, and that, in the so-called in considerable quantities, especially in the stems of process of respiration (the giving off of carbonic acid reeds and grasses; it forms the glossy pellicle of the or oxygen, as the case may be) a certain degree of heat cane, and is sometimes found in the joints of the bamnis always evolved. boo, where it is deposited in a soft pasty mass, called The connection of electricity with vegetable growth tabasheer, which ultimately hardens into pure semihas recently excited the attention of physiologists; but transparent silica. Besides these earths, there are little positive information has yet been ascertained. various metallic oxides and salts, and the well-known It has been long known that growth takes place with alkalies-potash and soda. The physiological uses of 79 CHA;TIBE3 S'S INFORMATION FOR THE PEOPLE. such products are but imperfectly known to physio- assume, little is absolutely known. In a state, of nalogists. Ml~any of them-such as starch, gum, sugar, ture, certain tribes are limited to certain localities, and the fixed oils —directly alminister to the support these situations being characterised by some peculiarity of the young plant and to the formation of new tissues; of soil and atmospheric influence. If the conditions of while those which yield flavour and aroma seem to be soil and climate to which they are subjected remain connected with the preservation of plants, by protect- the same, the character of plants is nearly uniform or ing them from the depredations of insects and other stationary; and this may be always said of them in animals. Others, again —such as silica and metallic their natural state. But if they be removed from a oxides-give hardness and stability to the stems and poor to a rich soil, from a dry to a moist habitat, from branches; some give elasticity and pliancy to the young a warm to a cold climate, or vice versd, then their shoots, thereby preventing them from being broken by internal structure will undergo a change; and'this winds; and several-as tannin, for example-seem to change will manifest itself in one or other of their exadminister to the durability of the woody fibre by ternal characters. In some classes this change is most their properties of resisting putrefaction. evident in the roots and tubers; in others in the stems and leaves; while in many the organs of fructification MsETAsIORPHIOSES OF PLANTS. (the flowers and fruit) are the parts most affected. The metamorphoses of plants forms one of the most Sometimes this change of situation merely produces a interesting sections of vegetable physiology. Techni- more luxuriant development of all the parts of a plant, cally, it is termed Morphology-that is, a consideration without causing any abnormal growth of a. particular of the changes and transformations which various parts organl. Cultivation, and other artificial treatment, may of plants undergo, either from natural or artificial be considered as the cause of these irregular metamorcauses. W~e know, for instance, that many plants are phoses, which assume in some plants a wonderful demade to change their appearance and qualities by cul- gree of permanency, and may be transmitted to succestivation; that by grafting, hybridising, and so on, the sive races; though, generally speaking, if the artificial gardener can change the size, colour, and qualities of stimulus be not kept up, plants will return to their his fruits and flowers: and that analogous changes take normal or natural condition. There are no such roots place in a state of nature-such as the conversion of or tubers in nature as our cultivated beet, carrot, leaves into petals, and leaves and branches into thorns potato, and parsnip; no leaves like the thick succulent and spines. It is also well known that flowers become heartiyg# of the cabbage; no flowers like our double double by changing their stamnens into petals; and it roses, carnations, and ranunculuses; and no fruits or is from a knowledge of these facts that botanists have grains like our delicious pears, apples, and cereals. asserted that all the appendages of the stemn or ascend- Thie hybridism of plants is closely allied to the ing axis are modifications of a single organ, and may subject of morphology, and is, in fact, a transformation be considered as leaves adapted to a special puroose. of character produced by artificial means. As among This doctrine, at first broached by Linnnlus, and sub- animals two distinct species of the same genus will sequently expounded by the German poet Goethe, is produce an intermediate offspring-such as the mule, now very generally adopted. It is usual to treat this which is the offspring of the horse and ass-so among subject under two heads-namely, regylar nietamor- vegetables two species belonging to the same genus can phosis, or that connected with the structure and de- be made to produce a hybrid; that is, a new plant velopment of all vegetables; and irreqular metanmor- possessed of characters intermediate between its paphosis, or that which influences only a particular class rents. This power of hybridising is more prevalent of plants, or parts of those plants, and which occur among vegetables thamn animals; for the different speunder peculiar circumstances., cies of almost every genus of plants are capable of proRegula mnzetamorphlosis seeks for facts to establish the ducinff this effect, if the pollen of one species be put doctrine, that all the appendages of a plant have a upon the stigma of another. The union, however, call common origin with the leaf, and may therefore suc- only take place between nearly-allied species, occurs cessively assume the form and appearance of that pri- rarely amniong plants in a wild state, but is quite comnmary organ. The first protrusion of the plumnule fron'm mon among cultivated species. According to modern the embryo is leaf-like, subsequently true leaves are botanists, the character of the female parent predomideveloped, and from a succession of these are formed nates in the flowers and organs of fructification of the the stem. The branches of the stem take their origin hybrid, while its foliage and general constitution are fiom leaf-buds, and are again clothed with branches those of the imale parent. Hybrids have not the power and leaves by the same process as in the main stem. of perpetuating their kind like naturally - distinct As a branch proceeds towards the point of fructification, species; for, though occasionally fertile in the second the leaves assume the form of bracts; these, again, are and third generations, they have never been known to succeeded by the leaf-like sepals of the calyx; and next continue so beyond the fourth. But though incapable by the petals of the corolla. W~ithin the petals are the of propagating beyond a very limited period, the pollen stamens-which sometimes assume a leafy form-next of the parent species may be made to fertilise them, or the pistil, and ultimately the seed-vessels. Even the their pollen to fertilise the parent; but in either case seeds are but leaves in another form, embalmed and the new offspring gradually merges into the original preserved, as it were, for the reproduction of another species. Thus nature has wisely set a limit to the plant; and in many, such as the beech-mast, the leaf- intermingling of species, by which they are preserved lets of the embryo may be distinctly seen folded and from ultimately running into confusion and disorder. imbedded in their future nutriment. Thus the growth In an economical point of view, hybridism is of great and reproduction of plants may be regarded as a circle value to man. By a knowledge of its principles, he of leaf-like changes, the leaf, or some modification of it, has been enabled to modify the characters of natural being in all cases the organ which administers to the species, so as to adapt them to his special purposes; functions of vitality. We need not enumerate instances and thus have arisen most of those beautiful sorts and of these conversions, for every one who has intelligently varieties of blossom which now adorn the flower-garden. observed the common garden plants around him,: must So also by crossing varieties of the same species, our have sometimes felt the difficulty of distinguishing grains, fruits, and kitchen vegetables have been brought between calyx and corolla, must have seen stamens to a high state of perfection. The size of one species massume the aspect of petals, and not unfrequently the has been assiduously amalgamated with the durability whole floral organ appear green and leafy. And just of another; the beauty of a third with the flavour as there is an indubitable passage from leaves to every or odour of a fourth; and so on with other qualities. other organ, so smay any one organ be found to revert The principles of hybridism will yet be more extento the primary form of the leaf. sively applied; and it is not too much to expect that Of irregulasr metamorphosis, or those changes which the perfection of our field and forest produce will yet parts of plants, or classes of plants, may be made to rival that of our orchards and gardens. 80 SYSTEMATIC BOTANYo 2orANr-derivedc from the Greek word Botansi, a plant knowing the order, which is usually typified by some -is that science which includes the study and investi- common plant, he canrs predict as to its qualities —a gation of the Vegetable Kingdom. Vegetable Physiology species of information which the artificial system does — treated in the preceding sheet-is that department not attempt to convey. Jussieu's nlethod has been of the subject which explains the organisation and vital greatly improved since the time it was suggested, parfunctions of plants; Systematic Botanssy that which re- ticularly by the late Professor Decandolle of Geneva; cognises their arrangernent into orders, tribes, genera, and it is his modification of the original plan, with and species, according to their respective forms and some further improvements, which constitutes the most qualities. The former relates to functions which are generally adopted Natural Sy'stems of the present day. common to all vegetables, the latter takes notice only According to both systenms, plants are divided into of such peculiarities and attributes as serve to distin- classes, orders, genera, species, and varieties. A class guish one individual from another, or one family from consists of plants resembling each other in some grand another family. The vegetable kingdom is supposed leading feature, and as strongly differing fromr another to contain upwards of 100,000 species; and therefore, class as mammalia do from birds. Thus flowering plants without somle systeml of arrangement into smaller with one cotyledon, whose trunks increase in thickness groups and orders, it would be difficult to acquire a from within, as the palm, form a distinct class; while knowledge of the special characteristics of plants, or flowering plants with two cotyledons, and whose trunks to convey that knowledge to others by any process of increase by external layers, constitute another class. description. It is the aimr of Systematic Botany to ob- An o)rder consists of plants still more closely allied, so viate this difficulty, by classifying plants according to that many orders may be found in the same class. certain types and resemblances which are common to a Thus as ruminant or cud-chewing animals form an numrber of individuals; thus making one description order of mammalia, so do the leguminous or pod-bearequally applicable to a class as to an individual. ing plants constitute an order of' dicotyledonous vegeThe advantages of classification in lessening the tation. A genzus consists of plants so very closely allied, labour of memory and description becomes strikingly that they may be compared to members of the same apparent when we reflect on the difficulty which would family. The pea, for- example, constitutes a genus of exist were each plant to be known by an entirely dis- leguminous plants, just as sheep form a family of the tinct name. For example, there are many species of ruminants. A species may be compared to one of the roses, all of which are known by the generic term Rosa, members which compose the family;. thus the gardeneach harving a second or specific name to designate it pea and sea-pea are different species of the same genus. separately, as R. centi.folia, Pt. danmascenza, &c. Now if A variety is merely a departure from the common apa botanist hear of a plant called Rosa, though its spe- pearance of the species, as regards colour of the flower, cific name be quite new to him, he has instantly a height of stem, or the like-differences which arise general idea of what sort of plant it is, fromn his pre- from climate, situation, greater or less humidity of vious knowledge of the common characteristics which soil, and other accidental causes. The boundaries bebelong to the genus Rosa. The principle of classifi- tween species and varieties are often very vague, some cation is to assemble those plants which bear most botanists regarding those plants as species which are resemblance to each other; and this has been done in imere varieties; but much doubt might be removed by different ways by different botanists; each method attending to the fact, that a species reproduces itself being called the system of the individual who devised from seed, and is always persistent under the same cirit-as Tournefort's system, Linneus's system, Jussieu's cumstances, whereas a variety has always a tendency system. Of the several systems which have been sug- to revert to its parent species, unless propagated by gested, only two are in use at the present time - cuttings, and fostered by other artificial means. A namely, that of Linntcus, the great Swedish naturalist hybrid is a plant raised by fecundating the stigma, of (1707-1778); and that of Jussieu —or rather a umodifi- one species with the pollen of another-a process which cation of that of Jussieu-amn eminent French botanist, rarely occurs among plants in a wild state, though who, during the long period between 1770 and 1836, quite common in cultivation. In gardeners' catalogues, was closely engaged in improvingr the nomenclature hybrids are generally ranked as species; but unless and arrangement of the vegetable kingdomi. perpetuated by artificial processes, they all soon die The system of Linnaeus is founded solely on what out, or revert to their original stock. A cross-breed is a are called the sexes in plants-that is, on the number, plant raised between two varieties of the same species, situation, proportion, and connection of stamens and and generally ranks s as avariety. pistils, which are regarded as respectively the male When there are two botanic names to a plant, the and fenmale organs. This system appears at first sight first is that of the genus, and the second that of the extremely simple, as it depends entirely on counting species-as, for example, Quncrcus alba, the white oak. so mawny visible parts; but it is very uncertain, as the;Vhen three names are given, the third signifies that number of stanlens often differ, from accidental cir- the plant is a variety; and this is sometimes more cunistances, in plants of the same genus; and it tells strongly marked by using the contraction var. before nothing of the plant but its class and order, which the third name-as Quercus ilex var. crispa, the curledlead only to the discovery of its technical namle, as leaved variety of that tree. Unless, however, the vaplants of the most opposite qualities frequently agree riety be of considerable importance, the third name is in the number and disposal of their sexual organs. for the most part omitted in botanical catalogues, and This mode of classification is known among botanists the varieties indicated by figures, or by letters of the as the Sexual System, or the Artificial System, because Greek alphabet-observing that the species is always it is founded' on mere artificial enumeration, and not reckoned as one, and that the varieties begin with the upon natural qualities or resemblances of the plants figure 2, or the letter A. so arranged. That of Jussieu, on the contrary, is The primary arrangement of plants, according both founded on the natural analogies of vegetables; and to the artificial and natural system, is into those with the botanist who is acquainted with its principles can flowers and those without flowers. The first division, at first sight assign any plant to its proper class and or that which includes the flowering plants, is distinorder, as there is always a general resemblance among guished by the name PHiENOGAMIA, because in them the plants belonging to the same natural order, Again, the organs of reproduction are apparent. It compreNo, 6. 81 CHAMBERS'S INFORMATION FO:R THE PEOPLE. heads all the trees and shrubs used in the economical the fancy, and exercises the memory, without imlp.ovarts, all the ornamental plants of our gardens, and, in ing the mind or advancing any real knowledge; and short, all those that have distinct organs-as leaves, where the science is carried no farther than a mere sysbranches, flowers, and seeds. The second division, tematic classification, the charge is but too true. But known by the term CRYPTOGAMIA, embraces, as the the botanist who is desirous of wiping off this aspersion, name implies, those plants in which the organs of re- should be by no means content with a list of names; production are not apparent-as the lichens, mosses, he should study plants philosophically; should invesand seaweeds. They have no leaves, flowers, or seeds, tigate the laws of vegetation; should examine the in the common acceptation of these words, their fronds powers and virtues of efficacious herbs; should proor leaves being very different from those of flowering mote their cultivation; and graft the gardener, the plants; and instead of flowers, fruit, and seed, they planter, and the husbandman, on the phytologist: not are furnished with little cases or thecae, attached to that system is by any means to be thrown aside: withtheir fronds, and in these are lodged the spores or out system, the field of nature would be a pathless embryo plants, nminute as the particles of the finest wilderness; but system should be subservient to, not dust. Here the resemblance between the two systems the main object of, our pursuit.' ceases-their classes and orders being arranged on totally different principles. We shall present, in the first place, an outline of the Linnsean system, both on account of its priority and simplicity, and as an ini- N A N S S T EM. tiatory step to gaining a knowledge of the different The sexuality of plants had been discovered long forms of flowers. It is true that it is now disused by before the time of Linnmeus; but as far as is now most men of science; but for the reasons already stated, known, he was the first who suggested the adoption of as well as from the fact, that many excellent works this characteristic as a basis of classification. Accordhave been arranged on its plan, it is necessary that ing to his system, the vegetable kingdom is divided the general reader should have some acquaintance with into twenty-four Classes, founded upon the number, the its leading features. proportionate lengths, the connection, or the situation We must premonish, however, that Systematic Botany of the stamens. These classes are again subdivided has no very alluring aspect to a beginner. The great each into one or more Orders depending upon the numnumber of titles of the classes and orders, to say no- ber of the pistils, the presence or absence of a seedthing of the generic and specific names, is a bar to corm- vessel, its shape, or the number and connection of the mencing the study; but when set about in earnest, stamens, or on the arrangement of the florets. Termns first difficulties quickly vanish-the subject becomes compounded of the Greek numerals and the word andrica, every day more and more interesting; every new plant signifying man or male, are for the most part used to is sought and examined with avidity; research is no designate the classes; and similar compounds of these longer toil; and every accession to the previous stock numerals, and the word gynia, which signifies woman of knowledge is attended by fresh gratification.' The or female, are employed to designate the orders. The standing objection to botany has always been,' says following synopsis presents at one view an outline of White of Selborne,' that it is a pursuit which amuses the system: CLASSES. ORDEnS. 1. Monandria, - - 1 stamen, - - - has 2 —Monogyllia and Digynia, or 1 and 2 pistils. 2. Diandria, -- 2 stamens, - -... Monogyllnia, Digynia, and Trigynia. 3. Triandria, - 3 3-I-onogynia, Digynia, and Trigynia. 4. Tetrandria, - - 4... - - -... 3-onogynia, Digynia, and Tetratynia. 5. Pentandria, - -... 6-Mono., Di., Tri., Tetra,., Pentagynia, and Polygynia. 6. ilexandria, - 6... - - -... 4-Monogynia, Digynia, Trig-nia, and Polygynia. 7. ieptanc'ria, - - 7... 4-.Monogynia, Digynia, Tetragynia, and HIeptagynia. 8. Octandria, - - -8... - - -... 4 —Monogynia, Digynia, Trigynia, and Tetragynia. 9. Enneandria, - - 9... -3-Monogynia, Trigynia, and Hexagynia. 10. Decandria, - 10... 5 —Monogynia, Digynia, Trigynia, Pentag., and Decagynia. 11. Dodecandria, from 12 to 19..... 7 —Mono., Di., Tri., Tetra., Penta., Hexa., and Dodecagynia. 12. Icosandria,... 20 ormore,... on the corolla or calyx,... 3-Monogynia, Di.-Pentagynia, and Polygynia. 13. Polyandria,... 20 or more,... on the receptacle, - 6-Mono., Di., Tri. Tetra., Pentagynia, and Polygynia. 14. Didynamia, -.- 2 long and 2 short, -. 2- Gymnospermia and Angiospermia. 15. Tetradynamia, - -6... 4 long and 2 short,... 2-Siliculosa and Siliquosa. 16. Monadelphia, all the filaments united, - - -... 8-Tri., Pent., HIex., Ilept., Oct., Dec., Dodec., andl Polyand, 17. Diadelphia, filaments united into two sets,... 4-Pentandria, Iexandria, Octandria, and Deecandria. 18. Polyadelphia, filaments in three or more sets, -... 2-IDecandria and Polyandria. 19. Syngenesia, five stamens united by their anthers,. 5-Polyg.-Elqualis, Superfl., Necess., Frustan., Segregata. 20. Gynandria, the stamens growing on the pistil,... 3-Monandria, Diandria, and Hexandria. [nad. 21. Monecia, flowers with stam., others with pist. on same plant... 10-Mon., Di., Tri., Tet., Pen., HIex., Oct., Ices., Polyan., Mo22. Dicecia, stamens on one plant, and pistils on another, -... 13-Mo. Di. Tr. Tet. Pen. Hex. Oc. En. Dec. Do. Ic. Polyand., 23. Polygamia, unisex. or bisex. flowers on same or diff. plants,... 2 —Monaecia, Dimcia. [and Mdnadelphia. 24. Cryptogamia-inconspicuous flowers, -... 4-Filices, Musci, Fungi, and Algae (now extended). second order, DIGYNIA, contains seven genera, one of I.-MIONANDRIA. which is callitriclhe, the water starwort, frequently met Flowers with one stamen, and with one or two pis- with in our ditches. There is another plant, sometimes tils; thus constituting two orders, of which there are sown in borders as an ornamental annual, which also thirty-three genera, and above two hundred and fifty belongs to it-namely, Blitumn capitatum, the strawberry species. The first order, MVONOGCvNI A, contains many blite. Its chief ornament is its fruit, which is thickly set highly-ornaumental exotics, chiefly reed-looking herba- on its branches, resembling strawberries; hence its name. ceous plants, with large leaves, and showy flowers. The seeds II.-DIANDaIA. and roots of many of these are Flowers with two stamens, and with one, two, or three d >'Sy 1 used in medicine, as well as by pistils; thus constituting three orders, of which there, 0I & } the dyer —as galangale, tu- are upwards of sixty genera. The first order, MONO~1~!X 1 irmeric, arrowroot, zedoary, and GYNIA, contains by far the greater number of the Zingiber oqicinale, the common genera. Here we find the useful olive, the fragrant f Ap ginger of commerce. Their pre- jasmine, the lilac, the fringe-tree, the catalpa, and dominating qualities are aro- many evergreen shrubs. Nor are the herbaceous memDig yisa. Monoynia. matic. Several of the genera are bers of the order less prized: the wild and cultivated British-as hippuris, glass-wort, and wrack-grass. The speedwells, the delicate schizanthus, the showy jus82 SYSTEMATIC BOTANY. titias, and the elegant slipperwort, are some of the splendid waratab or Telopia speciosissima. Several choicest gifts of Flora. The rosemary, and the nume- fine ornamental Chinese shrubs-as the Ixoras, for rous species instance-belong to this class, as well as many hardy of sage, are plants, both shrubs and herbs, natives of Europe. The ranked in second, DIGYNIA, contains only four genera, one of this order, which is a British annual, Bsugonia tenuifolia; named though some have sugremoval of the latter Ti Digsid. l onogyni. lplant to the Tsigu. ignia. Mn% Monegynia. class DIDY- Tetraonogynia. NAMIA, because, in addition to the two perfect stamens, there are the rudiments of two others in the flower. after the celebrated naturalist Count de Buffon. The The second order, DIGYNIA, which contains only three witch-hazel, a hardy North American tree, is also genera, are properly grasses-as the Axnthoxanthzum placed in this order. The third order, TETRAGYNIA, is odoratumn, which so greatly assists in giving hay its also small, containing only eleven genera. Among agreeable scent. In the third order, TRIGYNIA, there these we find the well-known holly, which as a hedge are only two nearly allied genera-namely, piper and plant and ornamental evergreen is unrivalled. Its peperomia. The first is universally used as a spice, timber, when it has attained full size, is solid, white, and is extensively cultivated in the East Indies as a and of remarkably fine grain, and much used by musimost important article of commerce. cal instrument-makers and other artists. The common pond-weed, Potamogeton natans, so frequent in our slowIII.-TRIANDRIA. running rivers, also belongs to this order, Flowers with three stamens, and with one, two, or three pistils; thus constituting three orders, which V.-PENTANDRIA. embrace considerably more than two hundred genera. Flowers with five stamens, and with one, two, three, Almost all the grasses, as well as the grain-bearing four, five, or many pistils; thus forming one of the cereals, are found in this class. Nor are the other most extensive of the Linnuean classes. The first order, genera less remarkable for the beauty of their flowers, MONOGYNIA, iS particularly abundant both in genera than are the grasses and cereals for their usefulness. and species. Every description of flowering plant is The well-known crocus, the corn-flag, and iris, and found here-trees, shrubs, and herbs, terrestrial and many allied foreign genera, are among the chief orna- aquatic; trailers, creepers, and climbers; annuals, ments of our gardens, and which compensates in some biennials, and perennials; deciduous and evergreen. measure for their want of usefulness when compared The second, DIGYNIA, is also a large order, and comprises many beautiful and useful plants. Here we find the Asclepias, with its curiously-constructed flowers, and the no less remarkable Stao:elia, a family of leafless plants, but bearing flowers of uncommon character Trigynia. Dgyna Monogynia. Trigynia. Digynia. *enogynia. both in shape and colour, and moreover diffusing a with their associates the cereals. No class shows more scent so loathsome, that blowflies lay their eggs on decidedly the artificial character of the Linnean sys- the petals! Here also we find the remarkable Engtem than this; for assuredly the iris and wheat can lish parasitical plant the dodder, Cuscuta Euroaea, claim no congeniality with each other, either in exter- and the stately elm-tree, so useful both for ornament nal structure or constitutional properties; but these and timber. The third order, TRIGYNIA, embraces the having each three stamens, compelled the author to ornamental laurustine, the elder, and other well-known place them together. The second order, DIGYNIA, con- plants. The sumach family, so variously useful in the tains most of our common grasses-as millet, panic arts, is also ranked here, with several other genera of grass, bent grass, fox and cat's-tail, oat and cock's-foot inferior note. The fourth, TETRAGYNIA, contains one grasses, besides wheat, barley, &c. together with the genus only, and which happens to be a British plant, a far-famed sugar-cane, that source of wealth to the tro- beautiful inhabitant of pical planter, and indispensable' condiment in the diet our bogs and marshy! i 44, of all nations. The third order, TRIGYNIA, contains ground, known by the only twelve genera, most of which are aquatic annual sname of Grass of Parweeds; some are curious or pretty, but none are culti- nassus. There are four vated out of botanical collections. species of this plant al- R. comprising sixty genera, and is one of GYNIA, contains a good many plants, both native and the most important of the Linnuean foreign. The Cotyledons and Oxalises of the Cape of classes, as containing many of our Good Hope, and the Sedums of Europe, are most most useful fruits, as well as most numerous. The lychnis, mouse-ear, chickweed, and esteemed flowers. In the order Mothe common spurrey, are also placed here. The last NOGYNIA we have the gorgeous cacti, order, DECAGYNIA, contains only one genus, and that a cereus, epiphylluns, and opuntias; the foreigner-namely, Phytolacea, of which there are nine myrtle, eaugenia, and eucalyptus. Of or ten species. fruits we have the guava, pomegranate, and several others. In the Monoi XI.-)DO0DECANDRIA. second order, DI-PENTAGYNIA -that There is no plant yet discovered with eleven stamens, is, plants having from two to five pistils-we have the and all those of this class have the number varying pear, apple, quince, &c.; likewise the extensive genus from twelve to nineteen. The pistils are either one, Mesembryanthemum, of which there are three hundred two, three, four, five, six, or twelve; thus constituting and thirteen species. In the third order, PoLrGvYNA, seven orders, in which there are about fifty genera. Polygynia. Di-Pentagynia. Trigsnia. Digynia. Ionogynia. we have the rose, the strawberry, raspberry, and many The first order, MONOGYNIA, anmong many fine tropical others of great worth and beauty. plants, includes the celebrated mangosteen, said to be the most delicious and wholesome fruit in the world. XIII.-POLYANDRIA. The garlic-pear, and the showy British plant which Flowers having an unlimited number of stamens, ornaments the banks of our rivers during summer, the distinct from each other, and seated on the receptacle. 85 CHA43BETS'S INFOTbATIO A FOR THE PEOPLE, There are six orders in the class, and one hundred and calyx; in the second order they are numerous, and seven genera. The order MONOGYNIA comprises, among fastened to a filiform receptacle. many others, the caper-tree, the well-known poppy, the curious sarracenia, and the magnificent water-lily. To Xv.-TETRADYNAMIA. this order also belongs the Bixa orellana, the red pulp Flowers with six stamens, four of which are longer of which is extensively used by dyers under the name than the other two. Linneus divided this class into two orders —SILICULOSA and SILIQUOSA; the former being to0 tu;bi, a short roundish pod, and the latter a long one; but modern writers have discontinued this distinction, which ~~ 7 is specific rather than generic. Many of the plants are dietetic-as the cabbage, turnip, radish, &c.; and 9~ 3-X some are finely-scented and favourite flowers-as the.? i\rAwallflower, stock, arabis, rocket, &c. The seeds of several cruciferous plants yield oil of excellent quality. This is a truly natural class of plants, forming the Di-Triigynia. Ioellogynia. C}ruciferce of Jussieu; great similarity of the flowers, seeds, &c. being observable throughout the whole of the of arnotta. The second order, DIGYNIA, is well typified in the splendid peony, a genus which has been lately much increased by new varieties received from China and Siberia. The plants of this order have two pistils. The third order, TRIGYNIA, contains the beautiful lark-,1\\: spurs, the dangerous aconite, and the strong-scented w / Hibbertia. The fourth, TETRIAGYNIA, contains only two genera-the butter-nut, a tropical fruit; and the Drin2ys TWinteri, a tree allied to the magnolia. The fifth order, PENTAGYNIA, contains ten genera, of which the wellknown columbine may be taken as a type. The last Stamens and Seed-vessels. genera. The calyx is a four-leaved perianth, sepals concave, equal, and deciduous; corolla of four petals, claws inserted into the receptacle, limbs widening outwards, and assuming a cruciform direction; stamens six; filaments awl-shaped, the opposite ones shorter than the other four; anthers acuminate, often arrowhead shaped, diverging; pistillum germen superior, style short or wanting; stigma obtuse; seed-vessel is a Polyg in. Penltagynia. siliqua or silicula, of two valves opening at the base. order, POLYGYNIA, includes a great many fine flowering The stigma is commonly persisting, and forms the apex plants, both shrubs and herbs: among the former, the of the dissepiment, which is prominent beyond the marmagnolia is most conspicuous; among the latter, the gins of the valves. anemone and ranunculus are confessedly beautiful. Of early or winter-flowering plants, the aconite and helle- XVIo.-MONADELPHIA, bore are examples, and the globe-flower and marsh- The stamens are united into one set in this class, marigold are showy plants. which is divided into eight orders, founded on the number of the stamens, not on that of the pistils, as in other xIv.-DIDYNAMIA. classes; the whole containing one hundred and thirtyThe flowers of this class are generally ringent; they nine genera. have four stamens, two of which are suzperior; and constitute two orders, under which are ranked one hundred and seventy genera. The flowers of the fourth class have also four stamens, but these are of equal lengths; while in this two are long and two short. The calyx also is of one leaf, and tubular, divided into five or two-lipped segments, which are unequal and Octandria. Heptandria. Pentandrin. Triandria, persisting. The corolla is of one petal; the upper lip In the first order, TrIANDRIA, we find several beauticoncave, and sometimes bifid, the lower lip trifid. In ful Cape bulbs-as the Ferrsaria, Tigridia, Herbertia, the first order, GYMNOSPERnIA, the calyx is persisting, &c. The flowers nare not only of uncommon formrs, and becomes the seed-vessel, in which the seeds lie but curiously spotted or streaked with dark colours. naked. In this Of the second order, PENTANDRIA, the passion-flower is order we find the the most remarkable type. There is also the ~rodium' e! AX germander, la- or heron's-bill, a section of plants formerly united with ~'~' l\\'' vender, mint, the geraniums. The third order, HEXANDRIA, contains (VIIIIN7lD/1z,~~ \,l and dead-nettle, but one genus, and is so distinct in itself that it forms and many others an order in the natural system. It is a bulbousj olgetv\. W Iof similar cha- rooted plant, called Gilliesia granzinea, having grassracter: several of like leaves and curious flowers. The fourth order, them are useful I-iEPTANDRIA, contains the pelargoniunis, commonly?fiij9,// in cookery. The called geraniums-a genus of plants unequalled for Angiosperma. Gymnosperma. order ANGIO- immense variety of forms and colours. Of pelargoSPERIMA, SO called because though the stamens are the niums there are above two hundred and thirty-eight same in number and position, the seeds are differently species, and between three and four hundred varieties disposed, being contained in a capsule. Many of the already enrolled in books. They are chiefly natives of plants in this order are very beautiful; for instance, the Cape of Good Hope, and have long held a disthe bignonia, volkameria, antirrhinum, mimulus, &c. tinguished place among our greenhouse plants. The The common foxglove, Digitalis purpurea, so conspi- fifth order, OCTANDRJA, contains only two genera, which cuous in our hedge-banks, also belongs to this order, have eight stamens, united in one set or brotherhood. and is a good type of the whole. The seeds in the first The first genus is Aitonia, named by Linnseus in honour order are four, situate at the bottom of the persisting of the late William Aiton, Esq. royal gardener at Kew 86 SYSTEMATIC BOTANY. The second is Comosperman hairy-seeded shrubs from plants whose flowers have many stamens in many New Holland. In the sixth order, DECANDRIA, we find distinct sets. This disposition of the parts on which Polyandria. Dodecandria. Decandria. the true geraniums or crane's-bill. These are chiefly herbaceous plants, and found in many parts of the tem- Polyandria. ] ecandria. perate latitudes. The herb Robert is a common British plant, and is a good type of the genus. This order is, the order is founded, is exemplified in the St John's however, rich in showy plants of very differently-con- wort-a plant common in our fields as well as gardens; structed flowers, called poapilionaceous, or butterfly- and in greenhouses the useful and beautiful fruit-tree, shaped; their seed-vessels being pods. Hence we find the orange, affords a ready example. here the crotalarias, the common furze, broom, genista, laburnum, rest-harrow, lupine, and many other beauti-'XIXSYNGENESIA. ful plants, as well as trees, shrubs, and herbs. The This class contains all the compound or composite seventh order, DODECANDRIA, comprises twelve genera, flowers which form the natural order Compositea. The some of them highly ornamental, butthey are all tropi- meaning of the term Spyngenesia signifies to generate cal plants. In the eighth order, POLYANDRIA, many of together, the seed-bearing florets being all crowded our gayest flowering plants are arranged-as the althea, together on the same base or receptacle; or, more prolavatera, hibiscus, sida, silk-cotton-tree, the tea-tree, bably, from the circumstance of the stamens being and its magnificent congener the camelia, now so corm- united in a cylinder, and surrounding the style near mon an ornamental favourite in British gardens. All its apex. The peculiar arrangement by which syngethe orders of this class are rich in fine flowering plants; nesious flowers are distinguished from all others is and as a great majority of them are easily transported this, that besides the union of the anthers, the flowers from the countries in which they are indigenous, a chief or florets, instead of standing singly, are here congrepart of them has been long in cultivation in European gated; instead of each having a calyx and receptacle, collections. one calyx and one receptacle is common to the whole, whatever that number may be. The whole together is XVII.-DIADELPHIA. called theflower, as that of a daisy: the separate parts Flowers having two sets or brotherhoods of stamens. composing the disk of it are calledflorets. The flower In general nine are united together, with a single one by is supported on its exterior by a number of scale-like itself, which leaves, by some called calyx, but by others anthodiutm, is accounted and mostly attached to the outer rim of the receptacle, the second which bears the florets on its upper surface. The -a t, Hi brotherhood. florets, however, are not always perfect in themselves: The class some of them are of two sexes; others male, or female, contains one or neuter. On the difference of these in position and EI-exa,,tndria. Pentandria. hundred and character, the orders of the class are founded. The twenty- nine florets have a calyx which is superior, and becomes the genera, the flowers of which are chiefly butterfly-shaped. crown of the seed; a corolla which is of one petal and The first order, PENTANDRIA, contains only a single superior; the limb campanulate or ligulate; stamens genus-namely, the l/onnziera trifolia, an African an- five, filaments inserted into the tube of the floret; annual of no great beauty. The second, IIEXANDnIA, thers united by their margins in all bisexual florets; contains six genera, of which the common weed fumi- germen inferior, being a naked seed crowned with the tory is a good example. The third order, OCTANDRIA, other parts; style erect; stigma in two parts, each recomprises only four genera, of which the beautiful volute and divergent; seed single, either naked or milkwort is the most numerous and conspicuous. The crowned with the calyx, or with a pappus to assist the common one of this country is among the most inte- dispersion. The dandelion and thistle are familiar exresting, and is found on chalk hills or other dry situa- amples. This class contains two hundred and seventyseven genera, and upwards of two thousand six hundred and fifty species. Decandria. Octandria. tions. The fourth order, DECANDRIA, contains the greater number of the leguminous plants, or such as bear pods. They have all butterfly-shaped flowers, and comprise almost all our most useful kinds of pulse, forage plants, dyes, and many beautiful and valuable shrubs and trees. The pea, bean, tare, indigo, are ex-Superfun. Squalis amples of the order. The first order is 2EQuALIS, in which all the forets are of two sexes. It is very extensive, and contains XVIII.-POLYADELPInA. many very common plants-as the sowthistle, lettuce, This class contains all plants whose flowers have hawkweed, burdock, artichoke, &c. The majority of their stamens arranged in many brotherhoods. It is them are herbs, and many are annuals. The second divided into two orders, embracing about twenty order is SUPERFLUA; here we find plants, the flowers of genera. The first order, DECANDRIA, has the flowers which have the florets of the disk bisexual, and those with ten stamens in several distinct bundles or sets. forming the rays female, but which are impregnated I-lere are only four genera, all tropical plants; among by the anthers of the disk. This circumstance was them we find the theobroima, which yields the useful considered by Linneus as superfluous; hence the title. chocolate nut. The second, PoLYANnDRIA comprises This is also a very large order, and contains many 87 CHAMBERS'S INFORMATION FOR THE PEOPLE. useful as well as beautiful plants. Of the first, tansy beautiful, are excelled by those of the same tribe from and chamomile are examples; of the second, the America and other parts of the world. In the second helichrisums, xeranthemnums, and dahlias. The third order, DIANDRIA, which has flowers having two anthers order is FRUSTRANEA, SO called because the florets of seated on the pistillum, we find one of the greatest the disk are bisexual, and those in the ray or margin British beauties-namely, the ladies' -slipper, found neuter. These last, having sometimes the rudiments in damp woods, particularly in the north of England. of a pistil, but no other sexual organ, are said to The third order, HEXANDRIA, containing plants which be ineffectual or frustrated polygamy. The type of have six stamens seated in the pistil, has only one the order is the splendid sulflower, with which many genus-namely, the Aristolochia, or birthwort, a very of the same style of flowering plants are arranged, curious family of climbing exotics; one only being such as the rudbeckia, coreopsis, &c. The fourth found in Britain-namely, the A. clemnatis. This class consists of plants which have male and female flowers separate, but on the same root, and contains ten orders, and one hundred and forty - seven genera. It may here be observed, that in syngenesious flowers the unisexual florets stand separately, but are included in the same cover; here they also are separate, but in distinct covers. The first order, MlONANDuIA-that is, separate male flowers bearing one staNT c~coss,,tria. Fl lrustran.n. men-comprises five genera, one of which is the celebrated bread - fruit-tree, a native of the South Sea order is called NE1CESSARIA, because the florets of Islands. The only British genus arranged here is the the disk, or centre of the flower, being all male, it Zannichellia palusttsis, the common pond-weed. The is necessary that those of the ray or margin should second order, DIANDRIA, having distinct male flowers be female, in order that there may be perfect seed. bearing two stamens, contains only four genera, three Calendula and. arctotis, exotics chiefly from the Cape of them exotic and one British-namely, the common of Good Hope, are two of the most conspicuous genera. The fifth order is called SEGREGXTA, because the fiorets have each its ad' ] proper calyx (different from the perianthe of the floret), To..he........... a bovfbesides the common anthodium or exterior calyx; or there pin. henaidn. are several florets contained in each duckweed. The third, TRIANDIA, consisting of plan ts calyculus. All the having separate male flowers bearplants in this order ing three stamens, embraces a few Segre-atal. are exotic herbs and tropical trees, and a great many under shrubs, the globe-thistle being the most common coarse European grass-like plants. in British gardens. The cat's -tail and bur - reed are To the above five orders Linnreus added a sixth, common aquatics, found in many ml called MONOGAMIA, in contradistinction to the others, parts of Britain. The maize, or which are polygamous. The plants which stood in this Indian corn (Zea), also ranks in were such as had their stamens united, as in the other this order. Thefourth, TETRANDRIA, orders of the class, but had simple flowers, not aggre- includes all plants whose separate gated florets. The genus Lobelia was one, but which male flowers have four stamensis, as well as all the others (except one), now placed as the alder and birch; the box in the class Pentanclrics Ieonssogynia. and mulberry; the common nettle; and the well-known foreigner Al- XX.-GYNANDRIA. cubce japonica. The fifth, PENTANThis class contains plants which have their stamens DRIA, contains all monecious plants seated upon the pistillum, and comprises one hundred whose male flowers bear five staand ten genera. The species are generally herbaceous, mens. Theo amaranthusis most conwith tuberous roots, curious gouty or climbing stems; spicuous here. The sixth, HEXANmany are epiphytes growing on trees, or flourishing in DRiA, has separate male flowers, rotten vegetable matter in moist places. Some of their furnished with six stamens. Its flowers are splendid, many highly fragrant, and all of members are chiefly. palms, or allied remarkable conformation. The class is divided into to that tribe-as the cocoa-nut, sago palmn, and acrocomia. The Triandria. seventh order, OCTANDRIA, has separate male flowers, gi ~bearing eight stamens, and contains only one genus, ~ ~ ~~. the.Dsv;aua, a lofty tree, indigenous to Chili. The ilexaudm~im Diaiidiiai. Monamdiaim. three orders. The first, {MONANRnia, contains plants having one anther seated on the pistilluin, and corin- Pentandri. Tetdn prises some of the most attractive wild British plants- eighth order is ICOSANDRIA, containing plants which as the orchis, ophrys, epipactis, &c. These, however have male flowers separate, and bearing iiany stamens 88 SYSTEMATIC BOTANY. inserted into the calyx. Botanists have as yet dis- mistletoe, common in England on oak-trees, whitecovered only one genus which can with propriety be thorn, and particularly in apple orchards. The fifth placed here, and this is a tree fiom New Holland, Polyandria. Iexandria. Tetrnmdria. Triandria. called Athlerospesma moschlmta. The ninth order, POLY- order is PETX4NDRIA, the male plants of which bear ANDaIA, contains plants whose male flowers are separate, flowers having fivre stamens. It contains thirteen geand which bear many stamens seated on the recep- nera, among which are the well-known culinary vegettacle. It is a large order, and comprises the beautiful able spinach, and the no less valuable hop. The Begonia, the chestnut, beech, hazel, walnut, and, above Monadelphia. lIexandria. Pentandria. all, the oak. The tenth, MoNADELPHIAs-plants hav- sixth order, HEXANDRIA, bearing male flowers, having ing male flowers distinct, and whose stamens are united six stamens, comprises seventeen genera, among which at the base into one brotherhood-is the most exten- are six palms, some of them of stately growth, and sive, and contains some of the most magnificent forest- highly ornamental in their native countries. The getrees-as the pines and firs, larch, cedar, cypress, &c. nus Smila;t is also here, some of the species of which Here are also the gourd, melon, and cucumber, the yield medical drugs. The only British genus is the poisonous janipha imanihot, and the medicinal palma Christi. XXII.-DIMOCIA. This class is composed of plants which have unisexual flowers, not on the same, but on different roots. It is divided into as many as thirteen orders, and embraces upwards of one hundred genera. The first, order, MONANDRIA, consists of plants bearing unisexual flowers on different roots, those of the male plant having but one stamen. It contains only two genera, one Enneaidria. Octandlia. being the remarkable screw-pine: so called because the black bryony. Order seven is OCTANDRIA, the males of leaves resemble those of the pine-apple, only much which have flowers furnished with eight stamens. The larger, and they issue from the stem in a very different only genus is the poplar, four species of which are manner; that is, neither opposite nor alternately, but natives of Britain. The eighth, ENNEANDRIA, the male the last always a little to the left of the former, so plants of which bear flowers having nine stamens, conthat theyare expanded spirally like the worm of a screw. tains only three genera, two of which, the mlercury and frog-bit, are British. The third, triplaris, is an American tree, useful for its timber. The ninth order, (4~/ Diandria. Monandria. Dodecandria. Decandria. The second order, DIANDRIA, contains plants having DEC.ANDIA, the male plants of which have ten staunisexual flowers on different roots, the males bearing mens, contains five genera, all of which are exotics. two stamens, and comprises four genera, of which the One of the principal is the papaw, a large tree-like common willow is the principal; there being of this herb, bearing bunches of fruit resembling melons, genus no less than 167 species already described. much used in India. The tenth order, DoDECANDRIa, The third, TRIANDnIA-having male flowers on one the male plants of which are furnished with twelve plant, and females on another, the former being fur- stamens, contains six genera; aimong them we find nished with three stamens in each-contains twelve only one British, an aquatic, called the water-soldier genera, among which one is a conimon trailing plant, (Strlatiotes). Another is the menispermum, or moonfound ons our moist moors-namely, the crow-berry. seed, which, with all the others, is exotic. The The date-palm, so useful to the people in Persia, and eleventh order is ICOSANDItA, the male plants of which other countries where it grows naturally, belongs to bear flowers having above twelve stamens inserted in this order.- The fourth, TETRANDRIA, consists of plants the calyx. There are only three genera, none of which having flowers of one sex, but on distinct roots. The are British. Order twelve is POLYANDRIA, the male male plants have four stamens in each flower. This plants of which are furnished with many stamens, order contains fifteen genera, among which we find the fixed on the receptacle. It contains seven genera, all candle-berry myrtle, one species of which is found wild of which are exotics. Here we find Cliffortia, a genus in Britain —namely, the sweet-gale. It includes the common in our greenhouses. Also Cycas and Zamsia, 89 C BAMIBERS'S INFO A i0MATION FOR THE PE OPLE, plants of a singulahr character, to be met with in most THIE NATURAL SYSTEMr. St 0 g ~ ~ ~ ~ ~ ~~ "The NAatural System of Botany,' says ])r Lindley, y _ ~ _, cs-' ~,~ ~being founded on these principles-that all points of resemblance between the various parts, properties, and qualities of plants shall be taken into consideration; that thence an arrangement shall be deduced in which plants must be placed next each other which have the Polya~ndriza. Iceosjanrig. reatest degree of similarity in these respects; and that consequently the quality of an imperfectly-known plant collections. The last order of the class is MoNADEL- may be judged of by that of another which is well PHIA, the male plants of which bear flowers, in which known-it must be obvious that such a method possesses the stamens are united in one brotherhood. It com- great superiority over artificial systems, like that of Linnmeus, in which there is no combination of ideas, but which are mere collections of isolated facts, having no distinct relation to each other. The advantages of the Natural System, in applying botany to useful purposes, are immense, especially to medical men, who depend so much upon the vegetable kingdom for their remedial agents. A knowledge of the properties of one plant enables the practitioner to judge scientifically of: the qualities of other plants naturally allied to it; and therefore the physician acquainted with the natural sysMionadelphia. tem of botany may direct his inquiries, when on foreign prises fifteen genera, of very various bulk and manner stations, not empirically, but upon fixed principles, into of growth. Here are the magnificent Bourbon palm, the qualities of the medicinal plants which have been the lofty and symmetrical araucaria, the humble provided in every region for the alleviation of the mabutcher's -broom, the juniper, the yew, the nutmeg, ladies peculiar to it. He is thus enabled to read the and the curious pitcher-plant. hidden characters with which Nature has labelled all the hosts of species which spring from her teeming XXIII.-POLYGAMIA. bosom. Every one of these bears inscribed upon it the The class POLYGAMIA (a word signifying many mar- uses to which it may be applied, the dangers to be apriages) is composed of plants having both unisexual prehended from it, or the virtues with which it has and bisexual flowers on the same or on different roots. been endowed. The language in which they are written There is considerable uncertainty about the arrange- is not indeed human: it is in the living hieroglyphics ment of this division, because some of the genera are of the Almighty, which the skill of man is permitted not always constant in their modes of flowering; and to interpret. The key to their meaning lies enveloped even single plants will occasionally exhibit all the in the folds of the natural system, and is to be found characters by which the different orders are distin- in no other place.' Such a system as is here eloquently guished. The class is now divided into two orders, delineated we aim at rather than possess. All the and contains about seventy genera. modifications-and they are neither few nor unimThe first order, MONCECIA, comprises plants in which portant-of Jussieu's original plan which have been the polygamy is complete on one root-that is, where promulgated, are merely contributions to one great end; there are male flowers having stamens only, female and years of patient research, crowned by the most flowers having pistils only, and flowers in which the extensive powers of generalisation, must elapse before stamens and pistils are united. This is a very exten- botany can boast of a perfect system. Passing then sive order, and contains many highly-beautiful as well numerous recent suggestions, British and continental, as useful plants. Here are the mimosas, the acacias, we shall adhere in our brief exposition to that modifithe maples, the beautiful ailantus, and the mango. cation of the natural system which seems most appliThere are also a good many of the grasses in this order. cable to botanical works now in current circulation; and which perhaps is better adapted than any unestablished innovations to convey to the reader a general idea of -~i~ its principles of classification. According to the original system of Jussieu, all the known plants were arranged into a hundred Orders, be7;~