COLLEGE OF ARCHITECTURE LIBRARY Gift of Prof. Hammond Cornell University Library N 78.V24 1904 Nature for its own sake; first studies in 3 1924 020 494 187 Cornell University Library The original of tliis book is in tlie Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31 9240204941 87 xtC^ c. 1/ a_^_^_ X>y /c^ NATURE FOR ITS OWN SAKE FIB8T STUDIES IN NATURAL APPEARANCES BY JOHN C. VAN DYKE AUTHOB or " ABT TOB ABT'B SAKE " FOUR TH EDITION NEW YORK CHARLES SCRIBNBR'S SONS 1904 COFTItiaHT, 1898, BT GHABLES SCKIBNER'S SONS TROW DIBECTORV PHINTING AND BOOKBINDINQ COMPANY NEW YORK Co FRANK THOMSON WHO KNOWS AND L0VE8 NATUBB PREFACE The title and the treatment of this book re- quire a, tew sentences of explanation. The word " Katnre," as it is nsed in these pages, does not comprehend animal life in any form whatever. It is applied only to lights, skies, clouds, waters, lands, foliage — ^the great elements that reveal form and color in landscape, the component parts of the earth-beauty about us. In treating of this nature I have not considered it as the classic or romantic background of human story, nor regarded man as an essential factor in it. Nature is neither classic nor romantic ; it is simply — nature. Nor is it, as some would have us think, a sympathetic friend of mankind en- dowed with semi-human emotions. Mountains do not " frown," trees do not " weep," nor do skies "smile"; they are quite incapable of doing so. Indeed, so far as any sympathy with humanity is concerned, " the last of thy brothers might vanish from the face of the earth, and not PREFAOB a needle of the pine branches would tremble." " Nature for its Own Sake/* then, means simply that herein nature is considered as sufficient unto itself. The forms and colors of this earth need no association with mankind to make them beautiful. So far as application or illustration is con- cerned, my argument has no direct bearing upon any branch of science, literature, or art. I have used scientific facts occasionally to point a meaning without designing a scientific book ; I have in places spoken of literature, but the book is not an appeal to nature from those who have written about it ; and as for art, the word does not appear after this preface. Painters or writ- ers, with their truth or falsity of statement, are not my present concern. What, then, is the object of the book ? Simply to call attention to that nature around us which only too many peo- ple look at every day and yet never see, to show that light, form, and color are beautiful regard- less of human meaning or use, to suggest what pleasure and profit may be derived from the study of that natural beauty which is everyone's untaxed heritage, and which may be had for the lifting of one's eyes. In measure these pages are records of per- PREFACE JQ sonal impression, and must be so regarded by the reader. However objective in treatment one might wish to be, his point of view is always more or less warped by the personal equation, and I can pretend to nothing more than a — view. As the sub-title indicates, these impres- sions are general in character — in fact "first studies." The book is designed as an intro- duction to a subject which I hope to consider more fully hereafter. Sage Libsart, «• 0. V. D« New Brunswick, N. J. CONTENTS Chapter I. Pmre and Reflected lAgkt. — Our knowledge of light — ^How light is obstructed by atmosphere — ^Dust and vapor particles in the air — Pure sunlight violet- blue — White light the residue after filtering through the air — Differences in light — Shown in cleared air — And from mountain-tops — Earth coloring regulated by density of the air — Warm and cold colorings — The dust veil — Krakatoa and the red skies — Color in the tropics — And at the poles — Sunlight in summer — The dawn — In Egypt with its wings of light — In temperate climes — Flooding of the dawn-light — The sunrise — Sunrise colors — Noon- light — Its great beauty in the fields — The fall of light — Sunset — Red sun disks — Sunset colors — Spectrum colors on the sky — Sky effects — Twilight — Zodiacal light — The moon and its rise — The misshapen moon — Twilight and moonlight blended — Horizon hues at twilight — Star-light — Star-colors — Darkness of the upper space — Lights of the night — The great variety — Countless changes — Beauty of the world 1 Chapter II. Broken and Shaded Light. — Cloud light and the cloud veil — The lowery day — Eain clouds — Storm light — Night and storm clouds — Mists and fogs — Vapor lights — ^White horizons — Fog lights — ^Fog and smoke — Fog effects — Color in fog banks — Nature's delicate hues — Alternate sunlight and cloud light — Sun-bursts — The fall of sunbeams — Sun-shafts with rain — The sun " draw- zui XIV CONTENTS ing water " — Sun-bursts and flying shadows in Scotland — Moon-bursts and moon beams — Shaded light — The law of shadows — Electric-light shadows — Shadows lightened by light-diffusion — Shadows in hot weather — The colored shadow — Scientifically explained — Complementary hues in shadow — Necessary conditions of the colored shadow — Blue shadows on snow — ^Lilac shadows on clay and sand — The mixed colors in nature — Shadow complications — The shadowless day — Odd colors in shadow — Shadows of the moon — And of the stars 25 Chapter III. The Blue Sky. — Impressions of the sky — Transparency of the blue — Sky depth — Through the clouds — Sky reach — Sky lines seen at sea — Horizon lines — Sky lines seen from heights — Apparent changes across the face of the sky — Sky waves and undulations — The blue seen from mountain-tops — The Great Silence of the firmament — The blue seen from the valleys — Its changes by day and by night — The tenderness of its coloring — Our non-observance of the sky — And of sky tints — Alpine glows at home — Skies in different lands — Color changes through atmosphere — Season changes in the blue — Luminosity of the blue — Transmitted and reflected light — Sky lights on the earth — Reflection from the blue — Atmospheric reflection — The dawn an illustra- tion of atmospheric reflection — And also a symbol in natural religion 47 Chapter IV. Clovds amd Clovd Forms. — Cloud- making — Cloud forms — Why clouds float — Effect of the winds — Effect of the air-currents — Cloud caps — Banner clouds — Self-renewal of clouds — Clouds, how acted upon — How moved — Day and night clouds — Classification of the families — The cirrus — Whiteness of the cirrus — Color CONTENTS *V of the cirms — ^The cirro-strataB — Son and moon halos— The ciTTO-cunralua — Dappled and mackerel skies — The stratus — The strato-cumulus — The cumulus — Cumulus changes — Summer clouds — Heap clouds — Cloud illusions — The cumulo-nimbus — Silver linings — The nimbus — Forms of the rain cloud — Storm clouds — Scattering forms of cloud — Scud, wrack, etc. — The lightness and drift of clouds — Cloud fancies — Cloud splendor and coloring — Seen at sunset — Seen at dawn and at noon-time — ^Valne of clouds in landscape — Seen with a low sky line. ... 66 Chapter V. Ram cmd Snow. — The vapor-earrymg capacity of air — Condensation — Causes of clouds and rain — Eastern storms, how produced — Warm winds and cold mountains — In the high Alps — ^The rain-drop — Size of the drop — The first heavy fall — Thunder-storms — Lightning and clouds at night — Bain-fringes — Surrounded by rain— The rainbow — Three-day storms — Rainy days — After the storm — City vs. country rain — Hail — Its forma- tion — The hail theories — The falling stones — Snow-flakes — Snow on the mountains and rain in the valley — The first fall— Snow-storms — ^The blizzard — Flying snow — The luminosity of snow — Snow prisms — Brilliancy of snow reflectioa — ^The snowy landscape — Under moonlight — Snow lines — Snow colors and shadows — Swirls and drifts— In early spring — Nature's skeleton — Nature's awakening 88 Chapteb VI. The Open Sea.— Viret impressions — Sea-changes— Water forms — The strife of the sea— Its restlessness — Wind and wave — Wave crests — Storm I waves — The hurricane sea — The height of waves — Thickness of waves — Tropical swells — Lines of a wave — Northern and Southern waves — The undulation and wave XVI CONTENTS motion — Deptii of the andalation — ^liocal hues of water — Sea-floors and their influence on coloring — ^Deep-sea color — Gulf and bay colorings — ^Mineral hues in water — Color patches — Sea sawdust — ^Transparency of sea-color — ^Beflection from surface — The smooth swell on the Southern seas — Northern waters — Sky effects at sea — Sunlight on the waves — ^Moonlight on the waves — Cloud shadows upon water — Colored shadows again — Cloudy days at sea — The emerald-greens of storm — Atlantic and tropical waves — ^Following the equator 113 Chapter VII. Along Shore. — On the beach — ^The coaflt-wave — ^Why waves break — Dancing jets under a cliff — The size of coast-waves — And their power — Forced and wedged waves — The beach-comber — Water-mirrors on the beach — ^The undulation again — The rising of the sea — ^Thrust of the waves — Curves of sand beaches — Wave action on the rocks — Cliff undermining — Bock forms made by water — Pulpits, bridges, and caverns — Formation of sand-dunes — Sea barriers — Bars, lagoons, and marshes — ^The tides — Ebb and flood tides — The bare shores — Coast lines — Color and light upon the shore — Twilight colorings — Moonlight on the sea — The coast in storm — ^The whipped waves — The uses of storm — Without the sea 134 Chaptbb VIIL Rvmm/mg Waters. — The river at the sea— Meeting the ocean — The river's path — ^The Plain Track — ^Through the meadows — ^The river's basin — The sluggish flow — ^The Valley Track — ^The river island — Hurrying waters — New movement — The wear of water — The sculptor of the land — Valley and mountain carvings — Oscillations of the stream — Lines of the banks and the water — Color on the river — With snow and under ice— CONTENTS XVli Freshets — Floods — The Mississippi — The river as it was and as it is — ^European rivers — The Thames, the Bhine, the Danube — The Mountain Track— Brooks — The moun- tain-brook and its motion — ^In the ravine — The gorge Following the brook— By the waterfall— The cataract- Niagara — Brook reflections — The frozen stream — Purity of brook waters — The river's source — Catch-basins — The rivulet — The beginning of the stream 153 Chapteb IX. Still Waters. — Names of seas and lakes — Definitions — Lakes «s. oceans — The mountain-lake — Its various features — Purity and clarity of its waters— Lake charm and sentiment — Local coloring of the water — Colors of background — ^Local hue and reflection — Con- fusion of hues — ^Beflections — Seen at night — Confusion of reflections with shadows — Surface appearances and phases of reflection — On darkened waters — On strong- hued waters — Variations and distortions — The likeness inexact — The angle of reflection — Elongated reflections — The Angels' Pathway — Bomance — Moonlight on the lake — Material beauty of American lakes — ^Lake George a type — The pond in the forest — The prairie pond — In Indian days — Artiflcial waters — ^Venetian lagoons and canals — Holland canals — The mountain-lake once more — Its serene beauty 174 Chapter X. The Earth Fra/me. — ^Earth and sea — The earth's surface — Inequalities of the surface — The skeleton of the earth — Strength of the frame — Formation of the crust — Geological formations — Solidity of the earth — Permanence of the flat prairies — And of the primeval forests — And of the desert — The sands of Sahara — The vaulting of the globe — ^The nnderstructure of the Alps — The base of the Jungfrau from Miirren — Foundations of XVUl CONTEITTS monntains — The hardness of rocks — ^Nature's building principle — The self-supporting globe — The lines of the earth — Shadow of the earth upon the sky — The arch of the sky — Horizon lines at sea and on the prairie — ^The curred line and " the line of beauty " — The law of the circle — Shown in the forms of nature — And in the elements and the solar system — Circles in physical and intellectual life — The uttermost rim of thought — The vanity of progress — The uniTersal law 197 r Chapter XI. Mountains cmd Sills. — Mountain ridges — How the mountains are formed — The wrinkle or fold theory — The Alps — The age of mountains — Denudation and erosion — The old Appalachians — The worn-down mountains — Exposed crusts — Mountains cut out by water — The approach to the mountains from the plains — Seen from a distance — Mountain-climbing — The view — The panoramic scene — ^From the high Alps — The look down- ward — ^Distorted light and color — The look upward — ^The clouds and the sky — The mountains from the valley Mountain colors — The lower ranges — Sky lines — ^Moun- tains at sunrise — At noon — At sunset — The western barrier — ^Looking eastward at sunset — Mountain glow at sunset — The Alps in storm — Storm in the lake-reflection — Mountain individuality — Changes of form — Of color — Influence of atmosphere — Light changes — The green hills— English hills— New England ranges — Hills in landscape — The levelling down 213 Chapter XII. Plains and Lowlands. — Impressions received from lines— Valley silence— Echoes and rever- berations — Valley shadows — Sunset valleys — The age of the valley— The brook again — VaUeys in autumn and in winter- The valley home— The table-lands— In Mon- CONTENTS XIX tana — The Bad Lands — Colors of decay — Plateaus and steppes — The primeval tracts — The American prairie — Frairie fires — Treeless tracts — The roll of the divides and swales — Prairie wildness — Nature's revenges — The wil- derness again — Flat plains — Low-lying tracts hy sea or river — ^The livable lands — Sky and horizon once more — The marshes and meadows — Beeds and rushes — Flags — Beauty of the commonplace — The marsh landscape — Near to civilization — The bottom-lands — Swamps and jungles 236 Chafteb XIII. Ltaf cmd Branch. — The New World vegetation — ^The foliage in America — ^Timber growths — Variety of forests — Depths of the timber — The "Big Woods " — Botanical classes of trees — Tree characteris- tics — Tree forms — Branch ramifications — The pathetic fallacy — The so-called sentiment of trees — Life of the oak — ^Tree motion — Sounding-trees — ^Leaves in motion — Trees in storm — ^Winds in the forest — Bare boughs — In March — The March harmony — Warming color — The budding season — Summer foliage — Variety of the greens — ^Light transformations — Swift color-changes — The trees in blossom — Blossom storms — Autumn glory — Indian summer — The scarlet foliage — Harmony of the scarlet landscape — ^Nature's sacrifices — Tree contrasts — Tropical forests — American forests — ^European wood- lands 253 Cbapteb XrV. Ewrth Coverings. — Trees and shrubs — Bush growths — The substitutes of nature — Laurel and rhododendron — California chapparal — Sage brush — ^Up- land bushes — Common growths — ^Wild roses — Growths under shadow — ^Fem and bracken — Scotch heather — Heather color — Golden-rod — Blue asters — ^Bushel and CONTENTS flags — Meadow growths — The grasses — The earth-pro- tectors — Meadow and pasture — The natural vs. the artificial — Meadow flowers — The wealth of color — Past- ure changes — Nature's care — Cultivated growths — House and lawn flowers — The mosses — Moss structure — Moss colors and textures — Gray lichens — Bock-staining by lichens — The work of the mosses and lichens — ^Heat, light, and moisture — Nature immortal — The Great Peace 273 NATURE FOR ITS OWN SAKE NATURE FOR ITS OWN SAKE CHAPTER I PURE AND REFLECTED LIGHT A FISH at home under some ledge of rock in the depths of the sea, what does it know of sun- light ? Doubtless the pupils of its eyes con- tract and expand with the lights and shadows that break across the hills and valleys of the ocean world, but how dim must be those lights, how densely dark those shadows ! A ray of sun- shine passing through fiye hundred feet of wa- ter is broken, deflected, almost extinguished ; and the eyes that look upward toward the light through that great green lens of wave can gather but a faint glimmer of the truth. They are focused for the ocean depths, and when the fish is brought up to the open day the eyes are instantly set, and stare without meaning. The first flashing sunbeam doubtless shocks them senseless. The tr uth when revealed is blindin g, and our sunlight is final truth to the fish. Knowledge of light. NATTTRE FOE ITS OWN SAKE Atmotpher- ie obstruC' tltau. PoTtiela In the air. We have, perhaps, a contempt for the knowl- edge of light possessed by the inhabitants of the deep, bnt oar contempt is somewhat shal- low. F or we oarselTes are living at the botto m of an even greater sea — the vast. ja tinoRphBrip. o^cean. We are looking up to the light through countless strata of air that break and twist and shatter the sunbeam — looking np not through five hundred feet, bnt probably five hundred miles of air-wav e. Perhaps, were we brought up and out of our sea and into the regions of space, our eyes, too, might be blinded by the sharp shaft of a pure and clear sunlight. Our knowledge of it is only comparative, a step upward from that of the fish. The truth in the superlative de- gree will never be attained. Human eyes .^ave never s een pure sunlight, and that white light which we regard as such is anything but pure. It is not the sum of all radiation, as we are ac- customed to think, but the residue, that wh ich remains after the paBsageJhrough atmosphere. TEielSr'we'^eathe is filled with countless particles of dust, smoke, soot, salt crystals, vapor; and these particles break light into color by obstructing the beams. The sun ray is thus disintegrated as soon as it encounters our outer atmosphere. Some of it is practically PtIEE AND EEFLECTED LIGHT lost to ns in the apper air, and that which finally comes on down to the earth has to our eyes a prevailing whitish, reddish, or yellow tone, dependent npon the density of the air. If we could sweep away our atmosphere entirely, the light would appear bl uish and the sun itsel f YMet-| ) lue.* There is a pre dominance of vio- let and blue in sunlight , but the waves of these colors being the shortest and weakest in travel- ling power, are the first ones to be caught and absorbed by the upper atmosph ere. Held in check, entangled as it were, quantities of them are massed above us, making what we call " the blue sky." The yellow and red waves, having greaterJengtib_jjiljowe£jffiffi[]]ttK^^tt^^ penetrate the atmosphere deeper and come to us witElhe tal e''tImr^'°Bn'n'"is ye1Io^^ or, in combination with other colors, white. But the tale is deceptive. Sunlight in its entirety appears whiter and then bluer, in pro- portion as we rid ourselves of our atmospheric lens ; and the sky itself grows darker from the non-diffusion of the sun's rays. An ordinary rain-storm that clears the atmosphere will tem- * This is the conclusion of Professors Langley, Young, and other scientists sun would appear aa one~bf the blue stars If seen from a distant worldjjgur TioUtMu* nmlight. NATURE FOR ITS OWN SAKE Light tetn through clear air. Light tetn /Vom moun- tain topi. porarily make the sky and distant hills look bluer, the sun whiter, the light purer. Cold that is intense enough to rid the air of moisture will also make a noticeable difference in the quality of the light. In Manitpba , where the thermometer often sinks many degrees below zero, a bright winter day reveals an air the moist- ure of which is frozen into floating crystals of hoar-frost, the sky appears cobalt-blue, the sun is white, and when it rises in the morning it is accompanied by two sun-dogs or j^ajj^ei^, one on each side, and almost as brilliant as the sun itself. The result is a bewildering display of white light that borders upon blue. Every snow crystal glitters, the cup of the sky seems to be lifted into infinite space, the snow shad- ows are intensely blue, and the running waters are dark-purple in hue. As we rise above the denser strata of at- mosphere that lie along the earth, by ascend- ing mountain heights or otherwise, the light changes even more positively. From the top of Mt. Blan c the stars are seen at midday shin- ing upon a dark blue-violet field that extends down to the horizon ; from Pike's Peak the sky is seen to be of a violet hue at times, and not in- frequently blue-black ; and from Mt. Whitney PURE AND KEPLECTED LIGHT Professor Langley observed the sun go down, not gorgeous in color, but coldly luminous, with the dark sky crowded close up to the disk, and the zenith deep violet-blue. Whenever or however the thickness of air between us and the sun is decreased, the coloring of light changes, growing from a yellow flame somewhat like candle-light to something kindred to the blue- violet flame of the electric arc-lamp. The a tmosphere then is chiefly responsib le for the quality of our lig ht, and upon the clear- ness or thickness of the atmosphere depends also the quality of our coloring. K the air is comparatively clear, the light will be sharp and the prevailing notes of color in landscape will be blue and green, because the slightness of the interfering media allows the short color-waves of blue and green to come on down to earth in great quantities ; if the air is heavy with parti- cles, the light will be less intense.. and the note s of landscape will be yellow or red, because the density of the interfering media allows the stronger color-waves of yellow and red to pass through and down to earth, but obs tructs th e bl ues and green s. It is owing to density of at- mosphere that the heated portions of the globe, like Morocco, for instance, are less strong in Earth eolmr- ingrtgu- latedby Vis iemity of NATTIBE FOB ITS OWN SAKE TUdmt veil. Kraltatoa. coloring than the temperate New England, not- withstanding the intensity and the directness of the sun's rays near the equator. The heat of the equatorial region produces dryness of the soil, and dryness produces dust, which is carried up into the air by rising currents. This obscures and changes the color of light more effectually than perhaps we realize. Professor Langley tells us that from the top of Mt. Whitney he saw this dust lying below him like a great reddish mist suspended four or fiye thousand feet above the level of the surrounding country. It can be imagined that light streaming through such a mist must be not only obscured, but must give a coloring to the earth of yellow, orange, and red, somewhat as the coloring of a room is affected by red or amber glass placed in the windows. A practical illustration of a dust-laden at- mosphere and its color effect was shown us in 1883. The volcanic eruption of Krakatoa threw a shaft of fine ashes some eighteen miles directly into the air, where it was caught by the winds, and swept around the globe ; and for months this fine ash was slowly settling through the atmos- phere to the earth again. The result was a tur- bid air and an extraordinary series of red dawns PTTEE AND REFLECTED LIGHT and snnsets seen in many lands. In Spain, where I happened to be a year later, the dawns were the most ruddy I have ever witnessed ; and each night the sun went down hissing hot into the Atlantic like a ship on fire, throw- ing great flaming signals of distress far np the zenith as it sank. But while the dust veil may produce great mass and variety of colors, these are not neces- sarily of the highest intensity. The most brill- iant hues are to be seen where the light falls the cl^iTes^ and this is not in the heated tropics, but near the cold poles. The northern countries have not the many local colors of the tropical lands, but those they possess have more depth and clearness. No palm on the banks of t he Nil e ever had such brightness of greens as the^gine and the spruce on the NorwejgiaiiL,moa|ijaiBS. In upper Scandinavia the flowers are brighter, the sky and water deeper blue, the mountains purer purple, the sunsets more scarlet than in Italy, Greece, or Algiers. And we all know what report the arctic explorers have brought back to us of brilliant skies, flaming Northern Lights, and intense blues in water, ice, and snow seen in the polar regions. There is not the slightest reason to doubt the truth of the Color in, (he tropict amd atthenarth. Arctic colon. NATUEE FOB ITS OWN SAKE Sunlight in iUimnffK report. Theory and observation both confirm it. A red, a bine, or a green at the north is harsh, intense ; where near the equator it is slightly bleached or blended with other colors by reflection. That the latter is more harmo- nioas than the former is qnite aside from the present tale. The changes in color and light, and their effect upon the world about us, are things of which many of ns living in the temperate climes have small appreciation. Our conventional remark to a neighbor in passing, " A fine day ! " means merely that we find the weather normal and the sun shining. We have never stopped to study the varieties of illumination and hue that weave and interweave through that day. It is merely a glittering generality to us ; yet from dawn to dawn how marvellous is the light, how splendid is the coloring of a clear day in summer ! It usually begins with the faint graying of the eastern sky above the horizon, or it may be that the light appears at first high up in the sky. The air has been cooled and somewhat cleared by the night just past, moisture is more predominant than dust, and the consequent sky-color is gray or silver. The light soon extends down and PURE AND KBFLEOTED LIGHT around an eighth of the horizon circle, and then perhaps to a sixth of it ; or it may moant upward in the shape of a fan. Sometimes pale yellow is a predominant coloring, and in warm weather a rose hue is quite frequently shown. If the sky above the horizon is barred or streaked with clouds, almost any conceivable color may be reflected from them, dependent upon the state of the atmosphere and the posi- tion of the clouds. Again, if the air is dense with vapor or dust, the advance arms of the sun may be seen reaching far over the night like the silver shafts of an enormous search- light. These premonitory signs of the coming day are often extraordinary in their appearances. For instance, in Egypt, during the heated season, the dawn is not always the slow steal- ing of light along the horizon. On the con- trary, a single shaft like the pinion of a wing rises upward toward the zenith. In a moment another shaft begins rising by its side, and then another and another, until the whole half- arch of the heavens resembles two spread wings poised perpendicularly. These are, I imagine, thebiblic al wings of the morning that j^t o the uttermost ends of the earth. At other Hie dawn. Theiaumin Bgypt. 10 NATTTEE FOR ITS OWN SAKE Wing t of light. Theiavmtn temperate climes. times the Egyptian dawn shows a mild efEect of s nn-dog s, such as are frequently seen in cold, snowy lands. In the one case, the Egrhella are produced by ice crystals in the air, in the other case by dust crystals in the air. They are more brilliant from ice than from dust, and where with the one they centre in great spots of light, with the other they shape themselves into side illuminations that resemble wings spread laterally. These, I imagine again, are the wings of light supporting the golden disk of the sun, that may be seen to this day carved on the temple lintels of ancient Egypt. But the dawn in our temperate clime is not so unusual in appearance. It is with us the gradual expansion and intensifying of radiance. The light is a soft, lustrous one, illuminating the earth entirely by reflection. While the sun is below the horizon no direct rays can possibly reach us. The shafts are shot up against the blue vault, and from this trans- parent blue of atmosphere they are reflected back to earth. It is not a bright or sharp re- flection. The rays are bent and thrown back only by the infinitesimal particles that float in the upper air. Even when the shafts strike a cloud they simply make it glow like a great PUEE AND REFLECTED LIGHT pearl, and the glow is infinitely more delicate for its surrounding of translucent atmosphere. Yet the great vault is illumined, and, as the sun rises higher, far to the north and far to the south, half-way. around the circle, a tapes- try of silver and gold is weaving on a blue-gray ground, and the dark ultramarine of the west turns a shade paler and seems to lift into space as the light grows stronger. How like the flooding of the tide this light drifts up, and in this great aerial ocean bringing with it warmth and color ! Soundless and surgeless, rolling in waves too translucent to be seen, ris- ing higher and higher, yet meeting with no ultimate shore, how gloriously it sweeps up and over the world ! How swiftly even the "meagre cloddy earth" borrows a splendor from above and reflects the flush of light and color ! The mists stir, the trees tremble gently, the dew slips from leaf to stem, and the whole globe seems to awaken from slumber. There is nothing more beautiful in all nature than this flooding of light across the sky, across the earth ; yet even as we watch it a great change takes horizon and full upon thi TheflaocUns ligM. 12 NATUEB FOE ITS OWN SAKE TlietvnrUt. Colort under ivnUght. rock, splashing it with a pale golden hue. At once the hue begins to creep down from the mountain-top, striking the oaks and cedars one by one with yellow shafts until the whole hill-side is mantled with its color. Swiftly the light spreads to the valley, and in a few mo- ments it falls upon the fields and meadows. Im- mediately begins the phenomenon of light being broken and obstructed by opaque bodies such as hills and trees, and we have the effect of light-and-shade. Immediately, too, the swift vibration of those points of light productive of color is increased, and we have the brilliant hues that mark the earth under sunshine. Every lake and stream and open sea warms in color and glances the image of the sun, and every hill-side and mountain-crag receives the stain of gold. Not the great objects alone, but the infinitely little, the pale wind-flower, the lowly buttercup, the yellow-centred daisy, the tiny violet, the leaf-whorl of the moss, all put on their brightest garments, each one lifting its head to the sun as the great glory of the universe. As the sun rises higher the splendor becomes more widely diffused. The color of the rose leaps to a high pitch, the top of the willow is a PUEE AND REFLECTED LIGHT 13 mass of silver, the poplar seems to shake light Erom its leaves as though they were trembling little mirrors. By contrast the shadows across the lawn and along the mountain-side seem darker, though in reality they are lighter ; and bhe light itself may seem fainter because widely diffused, whereas it is stronger and fiercer. By ten o'clock the sun is quite high in the heav- ens. Heat is radiating from the earth. Strata of warm air are forming along the ground, moving uneasily hither and thither in their search for an exit through the colder air to the apper regions. Dust and moisture, too, are rising; and by noon perhaps there is a haze lying along the hills and meadows, the distant ralleys look gray and warm in the sunlight, the mountains beyond them are faintly blue, the sky itself looks yellow or rosy. Color is every- vrhere, more predominant than in the morning, but less contrasted, because the atmosphere has blended and toned all nature to its own golden hue. How different this hot light of noon from the dawn-light ! The latter is preferred be- cause it is soft and agreeable to the eyes, but it would be difficult to imagine anything more beautiful or more splendid than bright sun- TJie light at 14 NATURE FOR ITS OWN SAKE Beauty of the noon- light. The fall of light. light beating at midday upon a field of ripened grain where the fiery red of the poppy gleams in between the yellow stalks ; or again this same light falling upon fields of golden-rod or npon great masses of variegated autumn foliage. Blinding, too, as is the noon-light upon desert sands or prairie uplands or flat smooth seas, yet its breadth and intensity make it one of nature's great glories. And how invisibly it cuts through the air ! On yonder mountain we should notice falling rain or snow or even a slight thickening of the atmosphere ; yet all day long the sunbeams fall upon it and we cannot see them. We see the mark they make on crag and tree, we feel their absence when a cloud shuts out the sun ; but that is all. As the day wears on, the heat increases. The leaves of the trees and the flowers curl and shrivel, the air rises quivering from the dusty road, the sky grows more rosy — even iridescent. The ascending air-currents are active and the atmospheric particles more numerous. Hour after hour the aerial envelope grows denser and heavier, the shadows fainter, the light more diffused. At last, when the sun has fallen to the western horizon and throws its rays along PURE AND REFLECTED LIGHT 15 the surface of the earth, they pass through many miles of this heated dust-and-moisture- laden air. When they reach our eyes they tell the oft-told tale of the brilliant sunset. The pale grays and silvers of the dawn, produced by the sun's rays coming to us through a cleared and cooled atmosphere, have now changed to the golds and scarlets of the evening, produced by the rays coming to us through a heated and a thickened atmosphere. So dense is the air at times that the shafts of the setting sun may be distinctly seen radiating up the sky like the spokes of an enormous fiery wheel ; and again at other times the air may be so thick that it obscures the sun's rays, and we can see the red disk go down almost without a flash of light as though its own heat had consumed it. The glare and heat of sunset colors are per- haps more apparent than real. The same sun at the time it looks red to us may show the yellow of noon and the white of dawn to the people and the lands lying to the west of us. We are looking from a land of shadow toward one that is still in full sunlight, and the bright- ness of the sky-color is great by contrast. The colors and combinations of colors that we see on the western sky and clouds at sunset and The nmset. Red Sim dUkt. Suntet colmn. 16 NATUBE FOK ITS OWN SAKE Spectrum colors on the Iky. Svntet ekg ^eeti. twilight hardly admit of description. All hues, all tints are possible, and nothing is of long duration. The appearance is almost as tran- sient as the aurora, for it is shifting in position, shifting in light and color continually. When there are no clouds, the normal evening sky shows a continuous spectrum, and the order of colors begins with red at the horizon and ex- tends in successive bands through orange, yel- low, green, and finally shades into the blue of the upper sky. These colors are intensified or depressed by atmospheric conditions, and they are complicated by the appearance of clouds, though the order of their appearance even with clouds is usually maintained, the reds being the lowest down and the succession rising through the intermediate colors to blue. The most splendid evening effects are, gen- erally speaking, in the autumn, when with Indian summer there is much heat and dust in the air. Scarlets, carmines, rubies, and burn- ing golds are then apparent; After several days of rain have left a damp, thick atmos- phere, a clearing western sky with fleecy clouds will often show very brilliant yellows in bands, and in between these bands small spaces of malachite green. The winter and the early PURE AND REFLECTED LIGHT 17 spring sometimes show wreaths and scarves of yellow or red upon the clouds after sunset ; but as a general rule these are not the seasons for bright displays. The coming of the dawn and the passing of the sunset doubtless occupy the same length of time, but to us the latter often seems of shorter duration. At the equato r there is compara- tively no glow on the sky after the sun disap- pears. Almo st immediately upon the vanish- in g of the disk from view there is darkness. Along the coast of Norway one may see the after-glow upon the sky far into the night ; and farther up the coast the sun itself may be seen at midnight. The^a^eof J^£,^[25|2J15^ the inclination of its axis accountjEOTboththgse appearances. In the temperate zones we have something between the two extremes. The sun for some time after its disappearance from view keeps throwing light from below the horizon upon the upper sky, and thus produces the effect we call twilight. It used to be reck- oned that when the sun had fallen eighteen or nineteen degrees below the horizon the twilight ceased entirely ; but according t o astrqnojm ers it ceases whenever a star of thesixthn^a gnitude Twilight. 18 NATTJEE FOR ITS OWN SAKE TTieiOdi- ttcal Kght. Moonrite. first twilight is, however, sometimes followed by a second glow ; and after this has passed there is occasionally another light seen in the western sky called the zodiacal ligh t. This nsgallj ^formB it self i n th e shape of a pyramid, with_ its base toward the horizon and its apex extending zenithward along the track the sun has tiavfiraed. It is a paleneBuIons light, like that of the star clusters called the Milky Way ; it appears more frequently in the tropics than in the temperate zones, at dawn as well as at twilight, and is often referred to as the " False Dawfl.:iimd^theJ^JWol£s_JM The cause of its appearance has not yet been satisfactorily explained. N"o sooner is the sun gone (at times before it is gone) than the moon comes up beyond the eastern hills, at first rising slowly and then sud- denly bursting into view. If the day has been hot and dry the face of the disk is red or deep or- ange, abnormally large in appearance, and often bulged and misshapen as regards its circle. We are looking at it through that same lower stratum of dense air which has been rising all day from the earth, and is still rising though the sun has set. It is the dense air that gives the abnormal size and the ruddy color. As the orb rises PURE AND KEPLECTED LIGHT 19 higher in the evening sky and gets out of the range of this heavy air lying along the earth, the disk apparently grows smaller and hecomes clearer in light. The red and orange fade out, and we see what is called the " yellow moon." It grows still fainter as it rises toward the zen- ith and the earth's atmosphere clears and cools ; and when in the morning hours it sinks into the west, the disk is whitened and apparently shrunk in size. There is little color demonstra- tion as it nears the horizon again. It is cool and silvery, seldom red or yellow, and slips from view usually unnoticed. Moonlight is, of course, the light of the sun reflected from the moon. It is not reflected from a bright surface like water (there is no water on the moon) but from dull surfaces like rock ; and as a result the reflection is many de- grees feebler than its cause. Yet the moon has some surface gleam about it and is hardly like an illuminated transparency hung in the air. By comparison with the sun it has no sharp shafts and is so feeble that when sun and moon are both above the horizon the latter attracts no attention whatever ; but after the sun has gone down and the moon rising in the east mingles its light with the twilight of the west, it makes a TheyelUm moon. Twilight and KnotyrV' light blended. 30 K-ATTJEE FOE ITS OWN SAKE Soriam huet at twi- light decided impression on the landscape. The two lights together giye ns the most charming il- lumination imaginable. The expiring fire of the one and the soft glow of the other mingle in a strange amalgam ; and a lustrous light envelops the world as tender and as lovely as that reflected from mother-of-pearl. There is neither deep shadow nor sharp color ; and around the great ring of the horizon, stealing far up the sky, there is a vast blend and mystery of color. The molten golds and garnets of the west as they steal along the horizon circle to the north and south, change into opalescent tints of yellow, rose, and amethyst ; and the blue and silver of the east as they spread out to meet the flush of the west, pass through all the shades of gray, mauve, and lilac. For producing delicate tints of color there is no such light as this double il- lumination coming from the east and the west. Wonderful in their variety, more wonderful in their unity, these tints drape the whole circle of the horizon like a celestial tapestry. Never for a moment are they fixed or permanent. The great waves of light that came up the blue vault at dawn have calmed down to gentle undula- tions, but they still heave and roll along the ho- rizon-walls, and at every heave some beautiful PURE AND EEPLECTED LIGHT 21 combination of color breaks and disappears, some equally beautiful one takes its place. And wben the sun and its cloud coloring have gone, when the moon is not in our quarter, then falls the night shadow upon the earth and through it the shining of the stars. They, too, are affected in appearance by the density or the clarity of the air through which they are seen. The night sky hanging over Sahara is usually a very dark purple, but the stars do not shine brightly upon it, and they have no marked col- orings; yet they appear very near, as though one might reach them with an arrow. "Where the air is more transparent, as in the north of America, the night sky is deeper, tEestars spame~and throw out t iny shafts of ligh t, and they show to the eye different hues of em- erald, topaz, amethyst, ruby ; but they do not appear to be at all near us. Jewels shining through a dusky veil, they have but little light, and that in such small points that the impres- sion upon the great mass of shadow lying across the earth is not great. We are able to see about us on a starry night, but is it by the light of the stars alone that we see ? Is that light suf- ficient to illumine the world even in a feeble way ? At night one-half of the globe is shut starlight. Star colors. 22 NATURE FOE ITS OWN SAKE DarlmMi q/tpaee. Other lightt »f the night. out from the direct light of the sun, and though far above the shadow, aborejhejjtmospheric arnh we call the-sky, the light streams through the realms of space, yet it leaTCS no visiblejraek, no illumination, no reflection. Beyond our sky it is supposed there is no air, no vapor, no dust to catch and to reflect light. In spac e the sun 's rays travel direct with no diffusion, no halo, no radiation ; and could we see the sun itself it would appear as an intensely bright disk with- out shafts. It would seem then that, with sun- light and moonlight cut off, we gain little or no light from the upper regions of space, save that which comes from the stars. It is possible that our upper atmosphere may be illumined by reflected sun rays or moon rays, and that thus the light of the stars is helped out. And it is possible, too, that there is something of stored- up light or electrical phenomena to add to the night illumination. These accessories may aid the light of the stars somewhat, but they de- crease — the total illumination decreases — as the night wears on and out, and the darkest hour yriii I irrrmii iiMiBM mm. . Ja Just before dawn . So much for the direct and reflected lights of a summer's day. It is one day out of three hundred and sixty-five, and has been de- PTJEE AND KEFLECTED LIGHT 23 scribed only in its general features. There are no two days in the year Just alike, nor will you eyer find one day paralleled or repeated in an- other day. There is a warmth of coloring and light in midsummer and autumn, a bleaching of hues in the spring, a coldness of light in winter ; but these again are only general char- acteristics of the seasons, and do not indicate the infinite changes in each separate day. The va- riety of combinations made by nature can never be tabulated or classified. Night after night one may watch the moon rise — watch it riding through clouds, first a dull disk, and then a growing light as it nears the edge of a cloud — but the same effect is never repeated ; never the same moon, never the same clouds, air, and coloring. The sun comes up, the sun goes down ; but each morning light sets a different glory upon the eastern sky, and each evening light reveals new iris hues upon the burning western clouds. And so with a different radiance for each hour the splendor of the world goes round, night following day, hemispheres of shadow alternating with hemispheres of light. As the earth turns, midnight and noonday slip over its surface. Kevolving around the sun in a slightly The gnat variety. Theamnt- lai chamgu. 24 NATURE FOE ITS OWN SAKE Th£ whirl- mgwm-ld. erratic orbit, flinging off heat or cold as the in- clination of its axis to the ecliptic, it follows necessarily that t he earth m nst .be.- Continn ally ch anging in light and col or. There shall never be any monotony so long as the sun lasts and the world spins ; and that light which was created on the earliest day is to this latest time the most varied and the most wonderful beauty of the universe. CHAPTER II BROKEN AND SHADED LIGHT All the lights that come from the sky and reach the earth, whether from sun, moon, or stars, are broken lights in the sense that they are somewhat shattered by passing through atmosphere. None of them reaches us in its purity ; yet, comparatiyely speaking, we say that sunlight is directligh^nioonlight is re- fleeted light, and cloud light is broken light. A cloi53nSelween the sun anathe earth is merely the interposition of a yisible atmosphere dense with particles of moisture, but it has a yery decided efEect in subduing the intensity of light and darkening the earth. The more vapor- laden the cloud and the thicker through its mass, the darker it will appear and the feebler will be the light filtered through it. If it is a large cloud it will appear, perhaps, unusually dark to us, for the reason that we can see only its shadowed base. On its upper part or top it is, of course, shining white in the sunlight, like the cumulus of a summer day ; for a cloud 35 Claud light. 26 NATURE FOE ITS OWN SAKE Thelmeery day. will hare its light-and-sliade like any other object, and the dark massed nimbns, which we call the rain cloud, is not very different from other clouds, save that its base is deeper sunk in shadow. The gray, lowery day, so often seen in spring and winter, shows us cloud forms so closely packed together that they make a continuous curtain across the sky, through which light passes to the earth in a neutral but widely dif- fused illumination. This is broken light in its most positive form. Dispersed in every ray by moisture particles, the crippled sunlight can do no more than throw a gray monotone over the face of nature, taking the cloud coloring for its chief note. Such a day is usually declared "dull." The sky and sun are completely shut out, there is no sharp flash of light, color, or shadow, no mellow haze upon the earth, no gilding and fretting of gold overhead. The cloud curtain covers the sky and draws down below the horizon-ring like a cap, a film of mist lies across the meadows, blue and purple drifts of air float high up in the valleys, and along the mountain-sides and over the craggy peaks hang gray fringes of rain. Upon days like these the clouds troop on across the sky, rank BEOKEN AND SHADED LIGHT 27 upon rank, one so close upon tlie heels of the other that they are scarcely to be distinguished. How often the traveller has seen them in Paris swaying above the Arc de Triomphe and drift- ing down over the Champs Elys§es, flooding the city with torrents of rain ! How often he has seen them defiling over the plains of Bava- ria, covering the Bohemian forests, or muf- fling the hill-tops of New England ! There is no break in the lines, no sunlight streaming through. At times a company seems to lift and lighten and the horizon appears to expand; but it is soon followed by a thicker company, the light darkens, the horizon contracts, and the rain waves through the air like the folds of an enormous mantle shaken out by the wind. And how dark the night following such a day ! There is no moon, and only the sharp- pointed stars illumine the watery canopy from above. On such a night the wind seems to rise as the darkness falls, the mountains fade into vague black spots and then blur out, the break- ers with phosphor-white crests fall heavy and booming on the sea-shore, and the forest moans and vibrates like a vast -^olian harp. There is little beauty here, save in sound and contem- plation. Not even lightning throws a momen- Storm light. Night and ttorm, cloud). 28 NATURE FOR ITS OWN SAKE l^ittt and fog: tary flash upon the scene. The swirl and the swish of the elements, especially on the sea or on the plains, the sublimity of the tempest, ap- peal to ns perhaps ; but our eyes are almost useless. Nothing so darkens the earth as night and rain clouds under a moonless sky. It is, apparently, a very different light that we see when the clouds are not above ns, but around us. A mist-. xitr-J.og_is_merelY a cloud formed close to the ground, and is not different f rom the_ claud that is about one atjtimes_onji mountain-top, except that the fog appears to be more luminous and to have more color. Doubtless something of this appearance is due to the thinness of the bank. It generally forms with a clear sky overhead, and is sometimes not higher above the earth than a house-top, though it is often a hundred or more feet in thickness. When the bank is shallow we are surrounded by diffused and refracted light, and an upward glance in the direction of the sun shows ns a white light seen as through alabaster. This same light is sometimes seen in the early morn- ing illuminating the whole landscape when the fog has lifted a thousand or more feet above the earth and is spread out into a thin, gauze-like sheet. The thinness of the sheet prevents ob- BROKEN AND SHADED LIGHT 29 scnrity and fa cilitates diff asion, as does a gron nd- glass globe npon a lamp . The result is a vapor- like light of marvellons luminosity and great beauty. Unfortunately it is not of long duration, and here in America it is not often seen. In France along the Seine, in England along the southern coast, and in Japan it is of common occurrence. The^^so-called "white hgrizon" results from a similar set of circumstances. The vapor-laden atmosphere of the morning, seen in mass as we look toward the horizon, produces the white-light effect. Seen in the afternoon or at sunset, the same horizon shows rose, lilac, or mauve tints, because the vapor particles have been superseded, or at least alloyed by the dust particles, and the heat is greater. But to return to the fog along the ground, as soon as it begins to lift it becomes lighter and brighter until finally the sun peering through from above appears as a silver or pale-yellow disk without radiant shafts. The light grows more golden as the fog-bank decreases in thickness, until at last, the sun havin g bur ned its way through to the earth, we see the normal light of day. The fog then disperses in small patches, is evaporated and carried upward by rising cur- rents of air, and in a short time has disap- Vapor lightt. WhiU horUom, Fog light*. 30 NATURE FOE ITS OWK SAKE Fbg and tmoke. Fog tf'eeU. peared entirely. Of course the deepening and tlie thickening of the fog-bank enfeeble and gray the light. When combined with dust and smoke, as in large cities, it is sometimes dense enough to require the lighting of street lamps in the middle of the day. How it ob- scures the vision eyeryone knows who has been in London at such times, or has crossed on the Few York ferry-boats, with the pilots picking their way by the sound of whistles and bells. In such fogs a few feet are often sufficient to efface objects entirely. In the country a fog never appears to be so thic k as in the citY._i haftgh..mlQW maxsh places it banks up and obscures land and water very effectually. Seen from a high place look- ing down, the shore-fog is not unlike a cloud below one in an Alpine valley ; and with the sunlight beating upon it the fleecy spun-silver effect is just as beautiful on the one as on the other. There is no limit to the fantastic forms a fog will assume when seen from a height. At times when the dark tree-tops protrude above it the appearance is that of a landscape buried in snow, at other times the meadows seem flooded with milk-white water, or suffocated with drifts and currents of smoke. The small islands off BEOKEN AND SHADED LIGHT 31 the coast of Maine are remarkable for fog ef- fects, and in cold weather, when the fog turns the bare trees into traceries of frozen silver, the effect is truly splendid. But close contact with fogs in either city streets or country lanes is not a thing enjoyed by the average person. People grumble and cough and talk about "disagreeable" and "horrible" weather, but not one out of a hun- dred gets his head far enough out of his coat- collar to see the beautiful pearl-gray tints about him. Broken and obscured as the light is, it still comes through in minute reflecting points. There is nothing opaque about the bank. I t is luminous~always pand thougli' we think of it and speaEoi it as gray and monotonous in color, we have only to contrast it with engine steam to find that it is often full of delicate pinks, lilacs, and pale yellows, especially when it is lifting. These minor broken color-notes seldom attract our attention, and yet they are perhaps as refined tones as we shall find in nature's gamut, if we except the notes of the upper sky at dawn. It is curious that people do not see them, and still more curious that they fail to appreciate them when they are pointed out. The average person is quick enough to remark the red flame Color in fog hcmld} 32 NATUBB FOE ITS OWN SAKE DaicaU hues in tuiturt. Alternate light and ihade. of sunset, but he seldom sees the dove-colors and steel-bines that lie back of him in the east ; he sees a scarlet maple or an orange stain npon a hillside meadow in October, but he overlooks the silvery sheen of the wind-swept poplar, or the cloud-like surface of the Indian grass ; he is not blind to Niagara and the Alps, and all the " big things," but he has an unhappy way of never regarding anything that is not " big," and hence loses a great deal of pleasure in life which comes from discovering and enjoying the beauty of the so-called commonplace. Direct light does not necessarily mean a per- fectly clear sky, nor broken light a completely clouded one. There are days of alternate sun- light and cloud light ; and indeed, a blue sky with drifting clouds is more frequently seen than any other. The heavy cumuli that lie along the horizon like distant mountain-ranges with snowy summits are not very noticeable as makers of shadow, nor are the thin clouds stretched in strata across the upper zenith pro- ductive of anything but a general veiling of the light. It is the thick, ragged, or round cloud, drifting across the sky in flocks, that makes the sunlight come and go upon the earth. When each of these moving clouds is surrounded by a BBOKEN AND SHADED LIGHT 33 field of blue the shadow of the cloud is cast upon the earth in isolated silhouette. As the cloud moves, the shadow moves too, and we have that charming effect called the flying shadow. If there is a stiff wind blowing and the clouds are closely packed together with only loopholes of blue here and there, or if the clouds are long rolls of the nimbus with occasionally breaks in the line through which the sunlight falls, we then see that other charming effect called the sun-burst. The sun-burst is often seen in summer weather, especially if the day is hot, and the air is heavy with dust and moisture. Underjiuc^ conditio ns the bright beam thrust through a cl oud opening ma kes a Jacob's ladder of ligh t f rom heaven to eart h. The light falls in a shaft very much as the pinion of the Egyptian dawn rises toward the zenith, except that it is usually frailer and more golden in hue. And it always falls through the shadow cast by clouds just as a be am of sunlight flashes into a darkened roo m and is seen b ecause it is surrounded by dar k- nessr ''^W1Siia^ cloud passes across the face of the sun its edges may turn to molten silver and its thicker portions glow with light, yet the beam does not get through and the falling shaft ThesuVf bwnt. 34 NATURE FOE ITS OWN SAKE The fall of nmbeamt. SmiFthaftt mnAram. is not seen ; but jnst as soon as a flash from the sun breaks through a torn portion of the cloud, the shaft falls to earth and is apparent from its shadowy envelope. It appears to fall earthward in a straight line, buL Uke all. su n- beams^ in reality describes- a-C urye throu gh t fie lower atmosphere^ especiallj if the s un_is lo w in the heaven s. The trajectory is not point-blank, but falls short like a spent rifle ball. Yet this is not seen by the eye and is known only to scientific calculation. To all appearances the shaft falls straight and remains fixed. It is the shadow of the cloud that glides across the meadows, up the valleys, and over the mountains ; the sun-shaft does not shift except where it falls more obliquely as the earth rotates from west to east, or its direction is changed by cloud breaks. The sun-burst is perhaps seen more frequently during showery weather or with thunder-storms than at other times, and it is usually more lumi- nous after than before a rainfall. As the first- comers of the storm-clouds begin to cover the sun, the shaft is often seen in a yellow beam falling diagonally toward the earth. When the shower is passing and the sunlight begins to show again, the shaft reappears frequently in BROKEN AND SHADED LIGHT 35 the form of a white beam, stronger than the yellow one, because falling through denser moisture. There may be many of these shafts, and they may radiate in all directions from the sun, as one often sees at evening, when the west is barred or streaked with clouds. The reach- ing down of sun-shafts toward the earth, with or without a shower, is commonly referred to as the s un " drawing wat er." It is really the s un illuminatin g the dust o r moisture in the a ir, just as the rainbow, which spans the opposite heave ns from the sun, is but the sun's rays re- flectecTand yefraoSe3"Ta3S^^05t^ I^'y °" drops of rain. For variety in the display of sun-bursts I know of no country more interesting than Scot- land. In stonny weather at sunset the light falling through chinks of the clouds will often make a half-wheel or fan-shaped alternation of light and shadow most brilliant in its flashes of gray and silver. And again, I have never seen such effects of sun-bursts and flying shadows together as in the Grampians, particu- larly those more barren portions of the hills where the heather is absent and only a yellow- green of grass and a slate-gray of stone are seen as background. Over the slopes and down the Themm ^'■draviing water." Stni'bwritt inSeotlani. 36 NATUKE FOE ITS OWN SAKE Flying ahadmeson the moori. valleys the lights and shadows seem to wave in bands, like the streamers of the Northern Lights across the sky. The shaking shimmer- ing efEect and the alternate colorings of yellow, green, and gray, chasing each other across hill and dale, are most extraordinary in appearance. After watching them for a few moments, it is qnite impossible for the eye to tell whether the light, the shadow, or the color is flying. At other times, when the clouds are rounder and larger, their shadows slip along majestically from crag to lake, from lake to crag again, glid- ing noiselessly and without obstruction up and down and over the Scottish moors like dark peer- ing spirits seeking a hiding-place and never finding it. They roam restlessly on and on, until at last they spread out upon the flat North Sea and their dark forms, changed to lilac in hue^ go slipping over the waters to the east, still rest- less, still noiseless, still flying. In other lands the shadow is interesting to watch as it glides across the meadows covered with buttercups and daisies, and climbs the wooded mountains to vanish over the ridge ; but the bare hills and moors of Scotland always seem the best play- grounds for the sun-burst and the flying shadow. Light beams and flying shadows are some- BROKEK AND SHADED LIGHT 37 times seen under moonlight, but they are not so marked as those produced by the sun, be- cause of their want of definition. The moon- burst attracts little attention on the land ; and on the sea, where there is reflection from a ruf- fled surface, the spot made by falling light is apparent enough, but seldom the shaft itself. The light is oftenest seen far out upon the horizon, and is merely a flicker and a sparkle upon the water. As for the flying shadows of clouds at night, they are dark purple in tone and are sometimes weird in shape, but unless the night is very bright, they are not usually noticed. Shaded light is somewhat different from broken or clouded light. It is not produced by shattered parts of direct rays that steal through vapors and cloud-veils, but by widely diffused or reflected rays. The direct beams are usually cut off by an opaque substance, and the light in the shadow is received from the re- flecting sky, the air, or some other illuminating or light-diffusing body at the sides. The earth as a globe is a good illustration of this. It is light on one side, and its opposite side would be absolutely black were it not for such reflecting bodies as the moon, the planets, and possibly Moon-huritt and moon thadowt. Shaded light. 38 NATURE FOB ITS OWN SAKE Thelawof shadows. Electric- light thacUnn. the illuminated upper atmosphere — counting oat for the present the faint if direct light of the stars. Were it possible for a tree or a house to be in tEiTfar upper space wherejhere is no air, its sunlit side would ^^jo^sely brillia.nt and its shaded side coal-blasck j,,^t on the earth the shadow of a tree or house is illu- minated by the atmosphere su5r.ftfta3i»S«i.Ua»d by the side reflections Jhrown^ upon. jt. It is the diffused light, produced by atmosphere or otherwise, that makes a shadow luminous, and it is the sharp, direct light that makes a shadow dark. One may state a general rule in these terms : The greater the diffusion of light, the greater the expansion anOmminalToS^ofliE'ad- ows ; the sharper and more direct the light, the mgrTcontracte^^inTtTe'^EECT] We can see this well exemplified almost any night by studying the light of the electric arc - lamp . It is the strongest and the most direct artificial light we possess ; moreover, it is a white light, with much of blue and violet in it, and the shadows produced by it are very dark and clear-cut. Seen at night, these shadows cast by the bare limbs of a tree upon pavement or upon snow are precisely edged, have l ittle penu^ ra, and are almost inky in BROKEN AND SHADED LIGHT 39 their blackness. Gas-light will cast no such shadows, nor will the sunrnoFwitTTEearc- light itself when muffled by a white globe. Anything like thick atmosphere, a cloud, or a milk-white glass that will spread the light over great space will lighten and expand the shadows at once. He nce it is that on cold, clear days, when the re is little dust or vapor in the air to ' "•*• — II1MIIII— i um i III! 11 iriii I imiii' t*\ 'Ill nun f" — ' — " r di ffuse lig ht, the shadows are darker, shar per, and less noticeablejp their coloring thaiLat any other time, whilethehotj|;a;^Sj,,;wv^L,,;fligijJb^ In America the heated days of early autumn, so remarkable for their hazy envelope of air and bright coloring, produce odd changes in the illumination of almost everything in land- scape. The shadows become much frailer in body, more transparent in light, with very pro- nounced hues, especially in the tones of lilac and blue. During the three heated days of September, in 1895, I had the opportunity of studying color effects, in both light and shade, in the woods and fields near Princeton, New Jersey — one of the most brilliant spots in au- tumn I have ever known. The studies were interesting, but the material was so bewilder- ing in variety that I found great difficulty in Diffutitn of light. Shadows in hot weather 40 NATURE FOB ITS OWN SAKE Colored ihadowa. Scientifie theory. locating causes and arriving at conclusions. The trees, the bushes, the field grasses were already tinged with autumn hues, and these hues, enhanced by the heat, made the land- scape appear crude and violent in its coloring. No imaginable tint was absent from the scene, and the greens, reds, yellows, and oranges were flaring in their intensities. But what impressed me more than anything else was the iridescent coloring of the atmosphere, the wavering of the heated air, the faintness of the shadows and their pronounced body of color. The pre- vaili ng tints, in J ^g.^shadaws were Hlac^viplet, and rose. There were few shadoiys that .were colorless, and few, jf . a^Xj wberein- the Jacal color of the ground or object they fell_ upon was noTtwisted or distorted somewhat by a leflficted or a complementary color. It is not a new theory of science that every color casts its, complementary hue in shadow. The practical working of it may be frequently observed in nature. AjifeSSl pf white .paper catching the light from a red sunset will receive a green ^g^^vvfrom an object interposed be- tween the paper and the sun. The same red light of sunsetKffin'g upoii snow will some- times produce green in the shadows of trees BROKEN AND SHADED LIGHT 41 Compte- tnentary hues in and bushes. D r. Weir Mitchell has noted yachts at sea sailing in the track of a fie^ red san with the shadowed white sails showing " a vivid green:"* and I have seen more than once the white sails of yachts crossing a yellow sunset when the change to blue in the sails was strongly marked — blue being the complement- ary color of yellow as green is of red. Un- doubtedly the yellow sky at sunset is measur- ably responsible for the blues and purples of the mountains below it, and the more intense the yellow the stronger the blue-purple. JttjtJlfi..i''"*™'' sunset shows g reenish-yellow, the mountain s]^^H3IOSa3itTTfora^ge7the shadows will be cyan-blue ; and so on throughout the gamut each color will disclose its opposite in shadow. This is scientific theory, and it has been de- monstrated and proved true of nature when all the conditions are just right. The only trouble is the conditions in nature are seldom just right. Th e com plementary colori |^ g, jn t he shadow is appa r ent on l y on cer , |;ain days , and under certain lights, atmospheres, and temperatur es. It is an error to suppose that a color is always casting its complementary hue * Doctor wnd Patient, page 176. 42 NATURE FOE ITS OWN SAKE Necetsary conditiont of the cohni tlMdow. Blue thadowt upon snow. in shadow or, at least, an error to suppose that it is always apparent to us. There are in- fluences, too, such as the losaLxfilffiCJjLJiie ground and the skireflection, that may neutral- ize or utterly destroy the complementary hue. It might be thought that a yellow sun at midday would produce blue shadows under the green maple on the lawn, but as a matter of fact it does not. The color of the shadow, whatever it may be, is absorbed and lost in the green of the lawn upon which it falls. The same trge 8hadow_Jallinjg;^^on^9la5gj:a^ sandy road, will show blftea>r.JiJaa-3t„ojttfie ; but I do not think this is owing necessarily to the presence of the complementary hue. It is more likely caused by sky reflection, helped out, perhaps, by atmospheric reflections from the sides. The blue shadows jjpgn jnow, so common sky ; and the bluer the sky the more apparent the blue in the shadow. They are produced by sky reflection, and the sky coloring is faintly apparent on the snow in full sunlight, but more obvious, of course, in the shadow. These blue shadows are stronger at sunrise and at sunset than at any other time. Under a clouded BROKEN AND SHADED LIGHT 43 sky they disappear entirely, and only a gray effect is apparent. Jnst before dusk, when sometimes the clouds become empurpled, the whole body of snow will take on a purple re- flection. The same or a similar effect is no- ticeable in the sand dunes along the sea-shore, though sand is perhaps not so good a reflector as snow. I should account for the lilac shadow on the clay or broken-stone road in the same way. It is a mingling of local color with sky reflection and side lights rather than comple- mentary hue. A rough surface like a green lawn or a meadow will not show a jflJflied shadow at any time or under any conditions, so far as my observation goes ; and I believe the reason for it is that it has not a favorable sur- face for reflection. If colors were always pure, and if side lights, atmospheres, and sky reflections could be elim- inated, we should undoubtedly see the scientific theory of complementary colors always demon- strated in nature ; but the problem is compli- cated, and all talk about "pure colors " is mis- leading. Nothing is pure ; everything is mixed and alloyed. The neutralizing effect of side lights, complementary and reflected hues, and local grounds, puts scientific calculation out Lilac shadowtm clay and sand. colon in nature. 44 WATUKE FOR ITS OWN SAKE Shadow nomplica- of countenance. A pure color in nature is always more or less bleached, grayed, silvered, or gilded — changed at least from its original estate — by these conditions. What might be the green of a maple-tree lighted by sunlight alone is one thing ; what it is lighted by sun- light, sky-light, and reflected light from the earth, not to mention atmospheric influence, is quite another thing. When all the factors are considered, we have anything but a pure green in the tree. It is, doubtless, a mingling of many hues that favors the mauve, the rose, and the lilac shadows. But then, again, they seldom appear unless the day is hot and the air thick, which leads one to think that atmospheric re- flection plays some part in their production. The cause can be conjectured only, but there is no doubt about the effect. The Qfilcired shadow is a^ reality, though ,i±s„ recent 4igp,9yj^S!»,J2?8 people still somewhat sceptical about it. We have seen that clear light is favorable to the sharp-cut shadow, and that when the light is more widely diffused by atmosphere, or in- creased by reflection, the shadow begins to lighten, to become vague and soft on the edges, and to be enveloped by a penumbra. When the light is still more widely diffused and broken BROKEN AND SHADED LIGHT 45 by coming through clouds, it is commonly sup- posed that the shadow disappears entirely. We th jnk of a clo udy day as a shadowless da y, and pr actically itJsjQ^ ^Ihfi-flutlines-aLih&slMMJow are lost, an£_yet_^hej^^ldai£^^ wiirBut^ok^^D^it. The green maple on the lawn has its breaks of light and dark seen in the foliage, and its form is cast in shadow on the ground, but the latter is very faint. It is only by the generally darkened tone that we can detect the shadow on such a day, and even then there is little distinction in color between it and its surroundings. Sometimes at a distance the shadow will appear bluish, but that effect is atmospheric rather than reflective. Sometimes, too, odd colors will creep into the shadows when the sky overhead is clouded and there are spots or breaks of light along the horizon ; but when the whole sky is under a veil of cloud, the color of the shadow is practically neutralized, and takes its hue from the ground upon which it is cast. The conditions of shadow production under moonlight are similar to those under sunlight, except that the degree of both light and shade is largely reduced. That the direct moonlight produces color wherever it strikes the garment- The shadowless day. Odd colors in shadow. 46 NATURE FOB ITS OWN SAKE Sfoon shadows. Star shadmos. ing of nature is undoubtedly trnej but it is al- ways a subdued dull color. And the shadows, though they are luminous and not black opaque patches, have only dull shades of blue, purple, and gray. There isamodern_ tendency to see too much color in jmoonlightjzdn JEac±,^tQ..see more than_ reaJly ^istis. The old idea of the whiteness of its light and the blackness of its shadows has passed away, but the new idea has some extravagance about it. Colors of every kind under the moon are far removed from the feeblest of daylight tintings. Feebler still than the moonlight is the light that comes from the stars. The planet Venus and many of the fixed stars are bright enough to throw at times a long reflecting track upon ruffled water, but the colors produced by them upon landscape are blurred into smudges of dark purple and blue, and the hues" of the shadows are too vague to be seen. CHAPTER III THE BLUB SKY The two great expanses, the blue ocean at our feet and the blue sky over our heads, are both impressive in vastness — the ocean more than the sky, possibly because we are familiar with its extent and have felt its power. We know, in a vague way, that the sky is even vaster than the sea, that it is the open field leading into interminable space ; but its very obvious coloring, its apparent arch on all sides springing upward and inward from the horizon, its fixity, give us something of a false impres- sion. We are inclined to regard it as a great blue dome or roof, a something tangible that is aup portfld by thn borizon-rim. a c oncav.e .sm- face looked at instead of a vast transparency And there is some excuse for our regarding the blue sky as an actual surface. It is the outer envelope of the globe, and is made up of the blue rays of the sun reflected from atmospheric 47 Iw^ret- siong of the tky. 48 NATTTKE POE ITS OWN SAKE Transpmr- ennyof the Hue. Sky d^th. particles. These reflecting particles seen in mass apparently make a roof above us which looks to he ten or fifteen miles in height. It is merely an appearance, however, and our not too reliable eyes deceive us. It is known that the atmosphere is from two hundred to five hun- dred miles in thickness, perhaps more, and there is no demarcation line where the blue be- gins or ends. Nor is there any point in this blue where cloudiness, haziness, or opacity shows. There is not a blur or film upon it, save where it is influenced by earthly vapors and dust. The sky itself is everywhere transparent, else we should not receive light through it or see the sun, moon, and stars shining beyond it. The recognition of sky distances is not easily made by the eye. A glance upward may tell us of five or fifty miles, as our imagination rather than our focus is adjusted. Looking out and over a tract of earth, we conceive distance by perspective lines, by objects decreasing in size, by the diminution of color, and the in- creased thickness of atmosphere. They are all optical guide-posts by which we can reckon with depth and width. But no such conditions exist in looking skyward. It is true we are looking through thick air to thin air, and beyond that THE BLUE SKY 49 into black space, but the color gradations are so subtle tliat we do not perceive the changes from one to another. Clonds help ns somewhat in increasing the feeling of depth, for they are perspective points five or six miles on the way at least. Sometimes a pillar of cnmulus will rise in the air thirty thousand feet from base to top, and tracing this upward the eye may see far above it the drift clonds of the stratus, and still higher, like specks upon the blue, the fine- spun fibres of the cirrus. This will give some idea of distance, though it is not entirely satis- factory. The view from Alpine peaks, where we are already twelve thousand feet up, and see still far above us against a violet sky the white spirals of the ice clonds, is not more satisfactory, save that in the thinner and clearer air the feel- ing of space is greater, and the sky becomes more of a blue wilderness than a domed roof. We comprehend the breadth and reach of the sky perhaps as little as its depth. Our horizon is an apparent circle as our zenith is an imagin- ary point. The circle is twenty, fifty, or from high ground perhaps seventy miles in diameter, but we always see its outside limit — ^the com- plete circle — no matter how vast the view. Ifo- where is the eye so hemmed in, nowhere does Through the clouds. Shy reacK 60 NATURE FOE ITS OWN SAKE Skylines Ken at sea. the horizon-ring appear so small, as upon the open sea. The ship upon which we stand is the centre of a watery field, the mainmast points overhead to the centre of the bine firmament, and all around spreads the deep azure glow. Judging from vision alone the world appears very small. The uttermost rim is just beyond us. The ex- panse of the sea and the reach of the atmos- phere about the whole globe are practically un- felt. Even the height overhead seems greater than the sweep before and after us. The limi- tation becomes still more limited when the va- pors lying along the surface of the sea thicken the air and obscure the sight. We cannot as a general rule under favorable conditions see more than fifteen or twenty miles across sea water, and even in calm weather the horizon is often clouded by vapor banks that lie along it like a row of faintly seen hills. All this helps the illu- sion of being circled and shut in by the horizon. Then again the sense of distance by perspective lines is practically annihilated. Occasionally the skeleton masts and black trailing smoke of an ocean steamer, or the tower-like looking sails of a square rigged ship appear, and act as catch-points ; but these are slight, and as for ' aerial distance we recognize it only by obscurity THE BUTE SKY 51 of coloring, which at sea dulls the vision in- stead of clearing it. It is on the land, and from the monntain-top, that we gain the best idea of the round reach of the sky. From such an elevation we not only see hills and valleys stretching away and down the sweeping world-circle, but if the sky be spattered with the white cirro-cumulus clouds, driving along in flocks before the wind, these, too, will seem to slope outward and down- ward like the earth. The result is that the im- pression of expanse in sky and earth is prodig- iously enhanced. The view is awe-inspiring ; and it is not necessarily so because it belittles the objects directly below us, but because it gives us a larger idea of distance, space, and sweep. The world seems a greater globe, the sky becomes enormous, and the imagination rises to meet the new presentation. There is no feature of the earth that can be regarded as more fixed, more permanent, than the blue sky overhead. And yet it seems as though a strong wind might blow it away. Winds, however, have small effect upon it. Clouds and storms pass across it, altering and obscuring it to our eyes, but beyond the local disturbance we know the sky is as serene and Sky Una teen from heightt. Apparent changes in the Iky. 52 NATURE FOE ITS OWN SAKE Sky tcavM. unchanged as ever. It never seems to move, it never seems to shift ; and yet again, it is far from being an unvarying appearance. Sir Isaac Newton discovered years ago, from the twinkling of the stars and the shaking of shad- ows cast by high towers, that "the air is in a perpetual tremor." Down close to the ground on a hot day we can see, in little, this tremor of the air as the heat currents rise from the earth ; and the mixture and intermixture of hot and cold currents in the upper air, the blowing of winds, and the drift of clouds must shake and disturb the lower layers of the blue, though this dis- turbance is not often noticed by us. At times I have seen, or fancied I have seen, in studying the clear sky, what might be called waves mov- ing across it. The motion did not seem to be that of ringed waves, such as one sees when a stone is thrown into a pond, but of deep undu- lations of varying blue succeeding each other slowly like the heave and roll of a glassy sea. Only on very hot days has this effect been ap- parent ; and I would not be certain that it is an actual fact, for the eye after long gazing at light and color is liable to become confused and see falsely. Still, I have seen the appearance a number of times, and I believe it to be reality THE BLUE SKY 53 rather than illusion. What causes it I cannot say, but it would seem to belong to some shak- ing of the lower atmosphere, for I have never seen it from high mountains. The lower atmosphere is, indeed, responsible for most of the volatile capricious appearances of the sky. From mountain-tops the sky is not so changeable, the stars twinkle less, show- ing that the atmosphere is quieter, and the face of the blue more uniform and serene. It lies there calm as at creation's dawn, lighted as was the old Mosaic firmament, and studded with the same jewel-like stars. It seems above and beyond all local and temporary disturbances. Winds mark it not, storms are far beneath it, heat, dust, and moisture effect it but slightly. It pales and lightens under the sun, deepens under the moon, and darkens under the stars, but in other respects it shifts not. An enor- mous sweep of violet-blue, it rests, a type and a symbol of unchanging serenity. And oh, the mighty silence of the upper sky ! What a contrast it is to the noisy, wind-swept earth and the restless ocean ! Infinite realms of violet-blue sweeping outward and upward, yet from them comes only the Great Silence — the hush that tells of limitless space. No The Uue from, mountain- tops. The Great Silence. 54 NATUBE FOB ITS OWN SAKE The blue from the valleye. By day and ty night shock, no jar, no clash ; there are no hidden spots of earth so silent as the depths where the stars lie buried. This perpetual violet-blue glow, unmarred and unspotted by high light or shadow or vary- ing tint, save such as it receives from the sun, might be thought monotonous, did we always have it before us. But humanity does not make its abiding-place on mountain-tops. It prefers the valleys, and there the vapors and earth mists and dust particles produce a different- looking sky from that which is seen from the height of Mt. Blanc. It is fortunate that it is so ; yet, even in the valleys, people some- times complain (it is said that they do in South- ern California) of " the monotony of blue sky." In reality the " monotony " is not in the sky, but in the eyes that look at it. Seen through the lower strata of atmosphere, it is never the same for any length of time. Its form is con- tinually changed by clouds and cloud-flocks, new colors are being woven backward, forward, and across it, by shifting masses of atmosphere, its light is waxing and waning with the motion of the earth. There is a continuous weave and ravel of delicate-hued textures, and from dawn to dusk there is not a moment's pause. Sun THE BLUE SKY 55 flame shot through, earth reflection shot back, cloud light scattered between, all make their momentary impression ; and even at night, though the splendor is diminished, it is not extinguished. The moon lends a pallor to the blue, the Milky Way stretches its nebulous scarf across it, the Belt of Orion blazes out from it, the planets gleam on its dark ground, and through the long dusk of night the shift- ing splendor falls, the eternal round of beauty moves on. And by day or by night, seen from mountains or from valleys, what infinite tenderness in the blue ! Was ever depth and transparency of color so beautifully revealed, and by such subtle, elusive means ? Drifts upon drifts of air super- imposed one upon another, rings upon rings of illuminated atmosphere, rising higher and higher, and all of them deepening the tone, but never clouding its transparency. How far we seem to see into that blue, but there is no place where the eye reaches a background — ^no place where a basic color appears. It is always a spectral abyss — a blue dream resting above ns, which the mind of the human has never been able to grasp as a reality. It is not to be wondered at that the tender- Shifting iplendor. Tendernent of the blue. 56 NATURE FOE ITS OWN SAKE observance of the sky. Sky tints. ness of color and the varied hues in the sky are unseen by the average person. I have never met anyone, other than a scientist or a landscape-painter, who conld conscientiously say that he had spent five consecutive minutes of his life looking at the blue above him. Its colors are not violent enough, nor its changes swift enough to attract attention. A scarlet cloud draws the eye at once, but the clear sky, with the sun burning a great hole in the blue, and throwing off a ring of pale yellow light that radiates outward, decreasing in the most delicate gradations until lost in the pre- vailing azure, is scarcely ever remarked. From dawn to dusk pale tints of silver, lilac, and ashes of roses lie all around the horizon - circle, reaching up toward the zenith as though aspir- ing to be rid of earthly taint ; hour after hour the sky overhead is passing from dark blue to pale yellow, from pale yellow to amethyst, from amethyst to opal ; evening after evening the cloudless sun goes down, leaving pale bands of spectrum colors on the twilight sky, but all this is waste splendor so far as the average person is concerned. People have an unhappy fashion of seeing with their ears. Someone tells them of the Alpine glow upon the snow-cap of the THE BLUE SKY 67 Jungfrau and they go there to watch, perhaps days at a time, for its appearance, when they might see the same pink glow upon their own skies at home almost any summer evening. It is not necessary for one to go beyond the door- yard to see beauty. The open sky will reveal more varied lights and colors than anyone could schedule or tabulate or talk about in a lifetime. Seen from our valleys, instead of being a monotonous blue roof above us, it is, perhaps, the most changeable transparency that human eyes have ever looked at or looked through. But while this variety is true of any one patch of sky, it does not follow that all blue skies are alike, even in their variety. Atmosphere, upon which so much responsibility for light and color has been thrown, is the potent cause of many different skies over many different lands. In dry countries, where there is much dust in the air, the blue is often a pale turquoise, or if there is great heat, then it is pinkish, or rose- hued. One hears much in tourists' descrip- tions of " the deep blue sky of Italy," but if they mean by that a, pure blue sky, their descrip- tions are not accurate. It is oftener pale lilac, rose-hued, or saffron-tinted, and not to be com- pared in intensity and purity of blue to the skies Alpine glows at home. Skies in different lands. 58 WATUEE FOE ITS OWIT SAKE Color ehamget through at- Tnosphere. Secuon ehanget in theblve. of Scotland. In no warm country is there such clear blue sky as one may see in the northwest of America ; and if we may believe the descrip- tions of Dr. Nansen, the Arctic explorer, this blue grows more intense as we move toward the poles, until at last it becomes of that violet hue seen from mountain-peaks. The Egyptian blue is often "deep" when the air is clear and still, but with winds, heat and dryness it takes on a warm tone as though it were seen through a red dust -veil. A similar efEect may be noticed over cities like London, where smoke and soot are continually fouling the air. The blue has a suffusion of pink or copper-color that gives it a hot look. In moist climates like Ger- ' many or Holland, there are often very clear skies, but the moisture particles in the air usually tend toward the production of a pale, milky whiteness in the blue. Again, in all countries of the northern temperate zone the purest summer skies are in the months of May and June. After these months the hot and dry summer begins to pale the blue, and in the autumn, when the leaves are changing to gold and scarlet, the sky in perfect harmony becomes rosy and often opalescent. If people are little observant of the blue sky THE BLTTE SKY 59 in its color transitions, they are, perhaps, even less observant of its Inminosity or light-diffus- ing power. It is a popular belief that the sky is a screen or veil to the earth, and that its principal reason for existence is that it tempers light to human eyes by obscuring it. And that is partly true. But the blue also receives, dif- fuses, and transmits light. It is luminous, at times scintillant, in small bright points. By long and attentive watching one can actually see these little points of light twisting, curling, falling and disappearing quickly as though they were mere flashings of star dust. And this does not refer to that portion of the blue sky near the sun where shafts of light are thrown down, but to the portions far removed, which are seen, perhaps, when the sun itself is under a cloud. The pure blue throws out more light than we imagine. If a sheet of white paper be held under it, even when the sun is below the horizon and eliminated from the problem, it will appear much lighter than the sky. But is it lighter ? Paper is not a body luminous in itself. All the light there is in it is merely the reflection of what comes from the sky, and a reflection can never be so strong as its original, There is an apparent contradiction just herC; Luminosity of the blue. Bluetky and white paper. 60 NATUEE FOR ITS OWN SAKE Trans- mitted light Sky lights §n the earth. which may, perhaps, be cleared up by some such explanation as this : Glancing up at the sky our eyes look inevitably into the shadows of air par- ticles ; the light that comes to us is transmitted through and between the particles. Glancing down at the paper, we are looking into the high lights of the paper instead of shadows ; the light is now reflected instead of transmitted. It is because of the coloring of the blue, and the transmission of light in countless infinitesi- mal points through it that we fail to appreci- ate its luminosity, and yet next to the sun and its reflections it is the most luminous phenom- enon in the universe. It blinds the light of the stars so that we fail to see them in the daytime, and even the moon looks pale and wan beyond it until the sun has gone down and the light fades out of the atmospheric canopy. Upon the earth its effect is equally apparent. The snow reflects the light of the blue sky like the sheet of paper ; and the white daisies of the meadow, the white foam of the sea, and the sil- ver flash from still waters are but reflections of it. From mountain-heights at twilight one may see below in the valley the thread-like river, the white farm-houses, and the fields of yellow grain showing like spots of light upon the shadowed THE BLUE SKY 61 landscape. Whence comes the light thrown back to heaven by these objects if not from the blue sky OTerhead ? Because sky-beams do not fall like rain-drops we think, perhaps, they do not fall at all ; but their presence in reflection is about us on every hand. But possibly more beautiful than the trans- mission of light is its reflection as shown upon this same blue dome of air. When the sun is in the zenith all the light is transmitted, but when the sun is below the horizon its light is thrown up and under the blue and is reflected. Instead of looking into the shadows of air par- ticles we are looking into their high lights. This gives the effect upon the eastern sky that we call the dawn, and the more gorgeous effect in the West, called twilight. These two effects are the only ones that reveal fully the reflecting power of the sky. If we could rise above the earth and from the moon look out tow- ard this world of ours, we should doubtless see it muffled by a great luminous covering. The light from it would all be reflected and the white, misty air might completely hide the earth from view. It would not, however, be a brilliant or scintil- lant light. Like that of the dawn, it would be softly pervasive. The atmosphere from which Reflection from, the blve. 62 ITATUEE FOB ITS OWN SAKE pheric reflection. The dawn tight. the dawn is reflected is not hard or smooth like metal ; it is not so compact even as the softest, thinnest cloud of the stratus, yet what beautiful light it throws off ! The white light that hangs over a city at night when there is fog, caused by the glare of many lamps thrown back from the fog bank, is brutal and coarse by comparison ; and the ruddy sunset caused by dust and cloud is more palpable and less crys- talline. There is no glare or flare about the dawn. The light comes from a deep transpar- ency quivering under the rays of the sun, re- ceiving its illumination in straight shafts of fire, and yet reflecting it with a softness of glow that delights the eye by its purity and delicacy. Surely this light of dawn is the highest mani- festation of beauty in the universe. Colors do not equal it, lines and forms of cloud and earth are petty compared to it, shadow is its very antithesis. It is not wonderful that it should have been the inspiration of Orphic song and the symbol of deity in ancient religions. To- day it seems a sign of preternatural glory even to modern materialism. Not the sun itself, but its light (symbolic of the purity and lumi- nosity of Deity) bowed the head of Zoroaster. THE BLUE SKY 63 The faith is strange with us now, and yet how well founded it was in natural religion. In- stinctively all races of men, whether savage or civilized, lift the hands and raise the eyes toward the heavens as though beyond the blue dome rested the seat of final justice, and its shining light was a manifestation of Supreme Power. The spiritual in man has always looked upward and counted the future abiding-place as somewhere beyond that sky ; but the light wherewith God "covereth himself as with a garment" is no longer regarded as a token and a message — a call to thanksgiving and to prayer. The muezzin's voice, the angelus bell — some human ritual — now bends the knee where once the white dawn drew all eyes as to the open gate of paradise. In the long centuries of his- tory how many prophets and peoples have gone their way to the grave following symbols of their own making — devices that have turned to dust and mingled with human clay ! How many times has the old order changed ! How many times have new faiths, new symbols, new signs arisen ! Yet the light in the east has never changed, never lost its lustre. Its glory was from the beginning as it shall be to the ending. Modern science may write it down as In ancient religion. The dawn as a symbifi. 64 NATUBB FOE ITS OWN SAKE ficance of teauty. a material phenomenon, and modern creeds may discard its worship as idolatrous ; but priest and scientist, in common with all hu- manity, have felt its splendor and known its beauty. Was beauty then made for ashes, and has splendor no significance ? The aspiring soul will not so account them. It belicTes that He who stretched out the heavens as a cur- tain and laid the beams of His chambers in the waters makes Himself manifest in the splendor of His light, and in the beauty of its reflection npon the morning sky. CHAPTER rV CLOUDS AND CLOUD FORMS A CLOUD is always a clond, no matter by what name it may be called or what its form or height above the earth. The fog that knocks about our ears is made up of the same visible vapors as the heaped-up cumulus rising tower-like thousands of feet above us. That one lies along the ground and that the other rises to a lofty altitude is due merely to a differ- ence in temperature and density. Clouds are formed by sudden lowerings of the temperature of moist air; and this lower- ing of temperature is usually caused by warm air rising into higher altitudes^ expanding as it rises and cooling as it meets with the upper cold-air currents. The simplest and most fre- quent manner of cloud-making is this : The radiation of heat from the earth forms into a column-like current of air, and the natural tendency of this current is to push upward, seeking an exit into cooler regions. It keeps rising, expanding as it reaches thinner air, 65 ClouA- making. 66 NATURE FOR ITS OWN SAKE Why eloudi fioat. cooling and becoming moister as it meets with cold cnrrentSj until at last it attains a height where the dew-point* is reached. Then begins the change into cloud. The hot air of summer rising npward reaches its dew-point very soon, and the usual result is the formation of the large cloud which we call the cumulus. When there is little heat or moisture in the rising air, and no pronounced cold in the aerial regions through which it passes, as is often the case in the spring of the year, the air-current may rise to a greater height, and when finally the dew-point is reached the condensation appears in the form of the stratus or cumulo-stratus cloud. The dryer and colder the ascending current, the higher it must rise before it condenses ; and so at times it rises to the region of frost, then freezes into the thin clouds of the upper cirrus, which are made up of tiny ice-needles floating in curls and wisps against the blue sky. When once formed, the clouds are heavier than the air in which they float, and their nat- ural tendency from the moment of their forma- tion is downward and earthward. Knowing this fact, we are often led to wonder why they * See Chapter V. for ezplanatioD of the dew-point. CLOUDS AND CLOUD FORMS 67 do not fall, why they do not rest upon the earth instead of in the air. There are several reasons for their not doing so, and all of these reasons taken together may account for the ap- parent defiance of the law of gravity. Thistle-down will speedily find an abiding- place on the ground if there be no wind, but a gentle breeze will carry it drifting for miles, now high, now low, always soaring, sinking, floating. Something of this effect is produced upon the clouds by the winds and the moving currents of air. They are always forming and changing and being kept in motion by the winds. The travelling capacity of the difEerent cloud flocks is, as we shall see hereafter, much greater than is generally supposed. Another and perhaps more potent cause of certain clouds being kept above us lies in the warm currents of air that are continually rising from the earth and buoying them up, very much as the heated air from a stove or lamp- chimney may buoy up a feather. We can see this illustrated in the formation of the clouds that sometimes hang about a mountain's top. The warm currents of air in the valley seek to rise up the side of the mountain because it is a natural conductor protecting them in measure ^eet of the windt. m^eet of tkeair- ewrenU, 68 NATURE FOE ITS OWN SAKE CUntd caps. Banjier clouds. from sudden gusts of wind and cold. They rush up the mountain-side quite rapidly, as everyone knows who has stood there at noon- time and felt the draft upward from the valley. As soon as they reach the top of the mountain they are forced from shelter by the currents coming after, and meet with the cold winds above the peak. The result is quick condensa- tion and the formation of that cloud which is called the " cloud cap " or " night cap " of the mountain. It is broken and blown away by the winds continually, but it is also being con- tinually renewed by the ascending currents, so that apparently it remains stationary and in- tact. It does not sink down, because of its re- newal and because the currents in measure lift it up. Something of the same process is apparent in the formation of what is called the "banner cloud," which appears to fly out like a streamer from some of the Alpine peaks. This cloud is usually on the warm valley-side of the peak. The moist air from below rises along this shel- tered side to the tip of the peak before it is struck by the cold currents and condensed into visible vapors. Above it and at the sides the cloud is being cut off and drifted away by CLOUDS AND OLOTJD E0EM8 the winds. It is visible only where it clings to the lee-side of the peak, and it stretches out into the air as far as shelter is afforded it in the shape of a long, thin flag. At a distance it looks as though it were something perma- nent, whereas it is only a continnons-forming cloud cut sharp on its sides by the keen edges of the wind. But these illustrations are of exceptional clouds, and even with them the rising currents alone are hardly sufficient to account for their being sustained in air. The majority of clouds are formed in open space and their air-currents have no mountain-sides to protect them. Nor are the common clouds subject to such violent destruction as the banner clouds. Moist currents are rising, clouds are forming and reforming, changing, sinking, disappearing ; but they are not often slashed into strips by the winds. We must seek a third cause for their being sus- tained in air, and it has been suggested already by the word " renewal." Clouds after they are formed are practically self-renewing. When the ascending air-current condenses into cloud the heat of the air-current goes upward with a tendency to form newer and higher clouds as it rises ; but the moisture of the current, robbed Clmidi formed in open space. Self-re- rmcalof cloudt. 70 NATURE FOK ITS OWN SAKE Claud Stoonden- sation. of its heat, forms into tiny, cold-water globules which hare a tendency to sink down toward the earth. If the globules are large and heavy enough, owing to sudden condensation, they do fall to the earth in the shape of rain ; if they are small, as is usually the case, they no sooner sink down into the warmer air from whence they came, than they are evaporated and carried up to the top of the cloud, to be once more condensed into mist. The "re- newal " of the cloud then means that the water- globules are continually falling down only to be evaporated and sent up again for recondensa- tion. The cloud is always losing at the bottom, and its flat base shows the line where evapora- tion takes place ; but it is continually adding to itself on the top. The tendency of the cloud at the top is to form above itself drifts of higher clouds, but this is held in check by the loss of moisture, the dryness of the upper air, and the dissipating action of the sun's rays from above ; the tendency of the cloud at the bottom is to sink down, but this is held in check by the continual evaporation as the water-globules fall into the warmer, lower air. The cloud then, though in reality always changing, is apparent- ly stationary and without change. The ascend- CLOUDS AND CLOUD FORMS 71 ing air-currents feed it, and when these are withdrawn at night by the decreased radiation from the earth, the cloud sinks and disappears. Hence it is that when radiation begins in the morning with the warming rays of the sun, clouds are formed, and when it ceases at even- ing the lower clouds disappear and only the high and comparatively dry ones remain. The meteorologists have established four broad classes of clouds according to their difEer- ent forms, and the difEerent heights at which they are usually seen. The classification is largely for the sake of convenience because, as has been already intimated, clouds are substan- tially the same thing whether high or low in the air; and the different forms mn into each other so closely that it is often difiBcult to tell one from another. The four classes, beginning with the highest and ending with the lowest, are the cirrus, the stratus, the cumulus, and the nimbus. There are some subdivisions which may be recited in order, but the broad divisions are given at first to avoid confusion. The Cikkus (1) is the frailest and the lightest of all the cloud forms, and drifts at the great- est altitude. It is sometimes seen fifty thou- sand feet or more above the earth, though its Day and night cloudt. ClassificO' tUmof cloudt. 72 KATUKE FOB ITS OWN SAKE Xhecirrut. Whiteness of the