SJofeMff -B Ho 9^, >. New York State College of Agriculture At Cornell University Ithaca, N. Y. Library A Cornell University '9 Library The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924002955874 Weather AND Weather Instruments Published by laylcr Instrument Companies Rochester, N. Y., H. S. A. Copyrighted by Taylor Instrument Companies Rochester, N. Y., U. S. A., 1908 Tl-r S ^ Jll signs of rain Fail tn dry weather. "Fair Weather After You" — Shakespeare. HE atmosphere surrounding the earth may be regarded as an " ocean " of air extending upward from the earth's surface. Obeying the law of gases it exerts, in all directions, a pressure varying according to the density of the air. It is impossible to tell accurately to what height air extends. Formerly some authorities claimed eight miles, while others said forty to fifty miles. From calculations based on observa- tions of luminous meteors, it is now es- timated to reach a height of 125 miles. The existence of an atmosphere at more than a hundred miles above the surface of the earth is revealed to us by the phenomenon of twi- light and the luminosity of meteors and fireballs. Should you measure oil the " ocean of air " in layers of equal thickness, the top layer would nat- urally be lightest because it is not weighted down and compressed by any layers above. Each succeeding layer would increase in weight un- til the earth is reached. This layer is heaviest as it must support the ;D«™«i^osj]EMas«i^ «»,"»* entire volume of air above. i»vii,iT,cr.«M..}Ajiituic ..-^-. ■••« ....<« .... ■...■ J « ■» ■■• ■■-IM--^ a ■i- -.-^S»-... -ii-—- s ...jfi-- ■ . »ir ^4^^ V^ 4 WEATHER * THE AIR AT GREAT HEIGHTS. It is almost out of the question for man to ascend higher than five or six miles, because of lack of air to breathe. At six miles it is too thin to supply a human being with the requisite oxygen for breathing. At great heights the atmosphere becomes more and more attenuated, and thins out by insensible gradations into a perfect vacuum. There is no defi- nite boundary immediately below which there is an atmosphere, and immediately above which there is ~ none. The pressure at an altitude of a few miles is very small, the pressure decreasing' with increase in altitude, as the higher the ascent, the less air remains above. PRESSURE OF THE ATMOSPHERi;. The air at sea level (weighted down by the air above it) exerts a pressure of about 14.7 pounds per square inch of surface. The pressure on a grown per- son (average 16 square feet) would be about 35,000 pounds. Were it not for the ease with which the air (under this pressure) penetrates the body, very slight changes in pressure would prove disastrous. THE WEIGHT OF AIR IN POUNDS. Like terrestrial solids and fluids, the atmosphere is held in place by the attraction of the earth. As the area of the earth's surface is one hundred and ninety- seven million square miles, or seven hundred and Generally speaking, the fall of one inch in the barometer indi- cates a rise of about 900 feet in elevation : 917 feet above sea level the barometer falls 1 in. I860 " " " " " " " 2 in. 2830 ' " " " " 3 in. 3830 " " " 4 in. 4861 ' " " " " 5 in. MEASURING HEIGHTS 5 ninety quadrillion inches, the total weight of the atmos- phere is eleven and two-thirds quintillion pounds. Of the enormity of these values, some idea may be obtained by instituting a few interesting compari- sons. One million trains each composed of one mil- lion powerful locomotives would represent but the hundredth part of the weight of the atmosphere. A leaden ball equal in weight to the atmosphere would have a diameter of 60 miles. This law (decrease of pressure) being known, its principle is used in measuring the height of hills and mountains by means of simultaneous barometric ob- servations at the two points. A convenient approximate rule is the following: The height of a place in feet is equal to the product of two factors, the first a fraction equal to the difference between the pressure at the place and the sea level divided by the sum of the pressures ; and the second, the number 55630, when the average temperature of the air between the two places is 60°. The number in- "^ , , J- 1 1 »7 j: Mantel Barometer. creases at the rate of 117 for every degree above 60°, and diminishes the same amount for every degree below it. THE ANEROID. The word " Aneroid " is a Greek compound, ex- pressing "without fluid," thus distinguishing this bar- ometer from a Standard Barometer, which measures The average height of the barometer in England at sea level is 29.94 inches. The average height of the barometer in the United States at sea level is 29.92 inches. 6 WEATHER the pressure of the air by means of a mercury column. (See p. 94.) The Aneroid is so arranged that the pressure of the air actuates the upper surface of a vacuum cham- ber, which is perfectly balanced between this pressure and a main spring. The vertical action thus given to the vacuum chamber is multiplied and transmitted to an index hand moving over the dial, which has been graduated into divisions (inches and fractions of an inch) to agree with the scale of the standard mer- curial barometer, which is the recognized standard. EARLY WEATHER RECORDS. The earliest records of weather are found in mythi- cal stories, some of which still survive. In England and Sweden "Noah's Ark" is still seen in the sky, while in Germany the "Sea Ship" still turns its head to the wind before the rain. In Scotland the "Wind Dog" and the "Boar's Head" are still the dread of the fisherman, while such names as "Goat's Hair" and "Mares' Tails" recall some of the shaggy monsters of antiquity. It is said that some of the prognostics of the Greek "Diosemeia" (270 B. C.) are in current use at the present time, having been incorporated by Virgil in his Georgics and then translated into English. OLD WEATHER PROVERBS. The enormous extent to which such a foretelling has been carried on, is shown by the vast array of weather proverbs and adages handed down from the past, while the faultiness of their generalizations has Ijeen proven by the utter failure of most attempts at A cubic foot of dry air at 32° F. at sea level weighs 0.080728 lbs. PROVERBS 7 their verification. Among the most common of these wise sayings are those which assert a controlHng in- fluence of certain days over the weather for consider- able periods to follow. The most potent of these special days seems to have been sacred to some particular saint, and perhaps the most powerful of all in this respect was the far- famed St. Swithin, whose wonderful prowess as a rain-maker is shown in the verse : " St. Swithin's day, if thou dost rain, For forty days it will remain. St. Swithin's day, if thou be fair. For forty days 'twill rain nae mair." A class of proverbs has to do with some supposed relation between one meteorological condition and an- other soon to follow, or of certain conditions existing at one time of day being indicative of immediate change. As an example of the first : " A storm of hail Brings frost in its tail." ' If the rain comes before the wind, Lower your topsails and take them in; If the wind comes before the rain. Lower your top sails and hoist them again." " The rainbow in the morning Is the shepherd's warning, The rainbow at night Is the shepherd's delight." There are grounds for suspecting that the exist- ence of many of the most "catchy" of all the proverbs is due to the tendency which existed a century or two ago, especially in England, where the crop of sayings " Evening red and morning gray Are sure signs of a pleasant day." Or And: 8 WEATHER seemed "to be most prolific, of putting words together in such a way as to form rhyme, even at the expense of truth. A case in point, though not from weather lore, is the epitaph upon a seventeenth century tomb- stone in an English country churchyard : " Here lies the body of Thomas Wbodhen, The kindest of husbands and best of men." Directly beneath is the explanation : " His name was Woodcock but it wouldn't come in rhyme." THE INFLUENCE OF WEATHER ON PEOPLE. The records of the police courts of New York City, studied in connection with those of the Weather Bureau, show conclusively that not only on the hot day Ijut that during certain meteorological conditions, ( unknown perhaps by name to the author of " Romeo and Juliet "), was the " mad blood stirring."* Records of deportment in the public schools, of suicide, of death, of general health, and of the be- havior of the insane similarly studied, show unmistak- able evidence of a weather influence, and in spite of the fact that it seemed to Samuel Johnson a very sorry thing that " a being endowed with reason should re- sign his powers to the influence of the air, and live in dependence upon weather and wind," even the most phlegmatic of us must acknowledge the potency of the east wind and the leaden sky. It was not until 1643, twenty-three years after the landing of the Pilgrims on Plymouth Rock, that Torricelli discovered the principle of the barometer. Torricelli's great teacher, Galileo, died without know- * "I pray thee, good Mercutio, let's retire: The day is hot; .the Capulets abroad, And if we meet, we shall not 'scape a brawl, For now, these hot days, is the mad blood stirring." FIRST USE OF BAROMETERS 9 ing why Nature, under certain conditions, abhors a vacuum ; but he had discovered the principle of the thermometer. The data from the readings of these two instruments form the foundation of all meteorological science. THE FIRST USE OF THE BAROMETER. As soon as men began to observe the barometer attentively, they began gradually to recognize that the rising and falling of the barometer had an evident connection with the weather. It was the celebrated burgomaster, Otto von Guericke, of Magdeburg, who first used the barometer as a "weather glass." He ap- plied, even then, to his water barometer the "weather scale," which is at present in such general use, on which the highest reading occurring at any place is designated as "fine weather," the lowest reading as "rain and wind," etc. The barometer as a weather glass has taken its course throughout the world, and is to-day used almost universally. ROTARY MOTION OF STORMS. About one hundred years after the invention of the barometer (1747), Benjamin Franklin divined that certain storms had a rotary motion and that they pro- gressed in a northeasterly direction. Although his ideas in this respect were more important than his act of drawing the lightning from the clouds and identify- ing it with the electricity of the laboratory, his con- temporaries thought little of his philosophy of storms. It remained for Redfield, Espy, Maury, Loomis and Abbe, one hundred years later, to gather the data and completely establish the truth of that which the great Franklin had dimly yet wonderfully outlined. lowest barometer reading was taken at Galveston, Texas, during the year of flood, when the barometer reached 28.48 or nearly % lb. per square inch below normal. 10 WEATHER STUDY OF CONDITIONS AT GREAT ELEVATIONS. We have at present no method by which we can forecast the weather with absolute certainty even for one day in advance, to say nothing of longer periods. The Weather Bureau has established an Observa- tory at Mount Weather to study conditions of temper- ature, pressure, humidity and wind velocity and direction at great elevations to increase our knowledge of the laws governing the atmosphere, which should eventually enable our successors (if not ourselves) to add to the accuracy of weather forecasts and to make them for a longer period in advance. As one of the primary objects in view in establish- ing Mount Weather Observatory is to make a study of the relations existing between the various forms of solar radiation and terrestrial weather conditions, much attention has been given to the instrumental equipment and to securing men to study the variation in the amount of heat energy given off by the sun from day to day and variation in the amount of heat absorbed by the atmosphere. So important to the study of -the sun is a continuous record of the magnetic variations that one of the first steps in the establishment of, the Observatory was the installa- tion of a magnetic plant consisting Mantel Barometer. of the best modern instruments for the direct observa- tion and for continuous registration of the variation in the magnetism of the earth. A temperature of 111 de^ees below zero was taken at St. Louis, Mo., at an altitude o{ 48,700 feet. PREDICTIONS 11 Researches will also be carried on to determine the existence and measure the extent of probable direct relation between meteorological disturbances and mag- netic variations. AT PRESENT WEATHER PREDICTIONS ARE MADE: (a) From local observations and refer to the lo- cality where made. (b) From weather charts (covering an extended region) and refer to any region on the chart. (c) From weather charts in connection with local observation and refer to the region where the local observations are made. As storms occur where the air pressure is low, the aneroid not only determines the height of moun- tains but also forecasts the weather. " WEATHER " AND THE EFFECT OF THE SUN. We speak of weather as meaning the atmospheric condition as shown by the meteorological element of a particular time, for a day, a season, or even a year. Climate is the aggregate of weather conditions. The sun regulates our weather; it gives rise to winter and summer ; by evaporation it raises the aque- ous vapor into the air, and this vapor by cooling, pro- duces clouds, rain, snow, storms and hail; it is the primary cause of the differences in atmospheric pres- sure, and in this way produces the winds. This heating influence of the sun, as also its modi- fications by cloudiness, by the wind, by the change The sun setting after a fine day behind a heavy bank of clouds, with a falling barometer, is generally indicative of rain or snow, ac- cording to the season, either in the night or next morning. 12 WEATHER from day to night or from winter to summer, and by the properties of the earth's surface, which, consisting as it does of water and land either covered with vegetation or barren, has varying capacities for absorbing the sun's heat. This influence of the heat of the sun has been established with the most absolute certainty by the most exact observations. THE METEOROLOGICAL ELEMENTS. The meteorological elements are the temperature, the baro- metric pressure, the humidity, M'""""^' b=»°">""- precipitation, evaporation, the wind, the clouds and the electrical conditions of the air. Aerial Meteors are winds, hurricanes, whirl- winds, etc. Aqueous Meteors are fogs, clouds, rain, dew, snow, etc. Luminous Meteors are lightning, the rainbow and the Aurora Borealis. HOW TO FORECAST. To make a good forecast, it is essential that the observer take into consideration the direction and force of winds, appearance of the sky, humidity of the air and a comparison of the barometer reading with the indicated pressure for several days preceding. An important fact, too often overlooked, is that the Aneroid foretells, rather than indicates, weather The sun is the great source of light and heat, which is trans- mitted to the earth. It is 853,000 miles in diameter and spherical in shape. TAKING READINGS 13 that is present. The Aneroid generally indicates changes m weather 12 to 24 hours in advance. After "setting" the barometer if the hands at the next observation coincide, the barometer is "stationary." If the blue hand has moved to the right, the barometer is "rising." If it has moved to the left, the barometer is "falling " The ex- tent of the rise or fall being the dis- tance (in fractions of an inch) between the two hands upon the dial. The possibility is ahvays for a continu- ation of e X is t i n g zveather unless some phenomenon presents itself which foretells a change. EFFECT OF WIND. The wind which causes the barometer to rise and fall, has more to do with the weather than the prevalence or defi- ciency of simshine. The shifting of the Mantel Barometer. wind is the most trustworthy of weather forecasts. A very low barometer is usually attendant upon stormy weather, with wind and rain at intervals, but the latter not necessarily in any great quantity. If the weather, notwithstanding a very low barometer, is fine and calm, it is not to be depended upon; a change may come on very suddenly. 14 WEATHER A rise in the barometer shows that heavier air is drifting to a place just before . occupied by light air. As heavy air is air that has been condensed by cold, a rise in the barometer indicates a cold wind. A fall in the barometer «hows that light air is drift- ing to a place just before occupied by heavy air, or, in other words, a warm wind is blowing. A falling barometer usually indicates a high or a low atmospheric pressure existing near at hand. The fall is then due to the gradual drifting up of the lighter air and the drifting away of the heavier air in the giddy whirl of some aerial conflicts. A fall- ing barometer shows that lighter pressures are ap- proaching the station of the observer. WEATHER WORDS ON ANEROID USELESS. Whoever has provided himself with an instrument of this kind believes himself to be the possessor of a self-registering weather prophet, and is generally highly indignant if it rains when his barometer stands at " fine " or astonished if it is fine weather when the barometer says " rain." The reading 29.5 (29j4 inches) was at one time assumed to be the midway line separating "Fair" from "Rain" and was accordingly marked "Change." 30 inches was marked "Fair;" 31 inches, "Very Dry;" 28.5 inches, "Rain;" and 28 inches, "Stormy." A fixed standard was thus assumed for a condition of Nature that is literally as unstable as the wind. It was supposed that the instruments were to be used only in places about at the same level as the surface of the sea. One thousand feet of altitude represents, roughly, A sudden rise in the barometer is nearly as threatening as a sud- den fall, because it shows that the level is unsteady. WEATHER WORDS 15 an inch of pressure on the barometer. So that if two barometers were placed, one at sea level and the other at an altitude of 1,000 feet, the one at sea level might read "Fair," while the other, under practically similar meteorological conditions, would read "Rain." This is the ideal barometer, as the scale reads only from 28 to 31 inches, and has no weather words on it. Even at the sea level, if a barometer which has been standing at, say, 30.9 inches for some days, suddenly fell to 29.9 in 24 hours, it would ALTITUDE. The scientific word for ** height." The altitude of a cone or pyra- mid is the height of its vertex above the plane on which it stands. The altitude of a star is its height above the horizon. The altitude of a mountain or hill is its greatest height above sea level. 16 WEATHER give a positive indication of change, intimating the approach of strong wind and probably rain, yet according to the dial, it would read "Fair." In a similar manner, if a barometer that had been stand- ing at 28 inches for some days, rose in about 24 hours to 29 inches it would indicate the approach of a cold, dry wind although the dial would read "Rain." It follows that these words on the dial have no significance but are simply relative. SINGLE OBSERVATION USELESS. A single observation of the barometer, without reference to the conditions prevailing at definite inter- vals preceding is liable to be misleading. The im- portant thing to know is— Has the rise or fall been a gradual one or has it been rapid? If the barometer is stationary, how long has this condition existed? Weather prognostications from barometer observa- tions are based on a knowledge of all these conditions, and never from a single observation. RAPID CHANGES INDICATE. A rapid fall or a rapid rise intimates that a strong wind is about to blow, and that this wind will bring with it a change in the weather. What the precise nat- ure of the change is to be must, in the main, depend upon the direction from which the wind blows. If an observer stands with the wind blowing on his back, the locality of low barometric pressure will be at his left and that of . high barometric pressure at his right. With low pressure in the west and high pres-. sure in the east, the wind will be from the south ; but with low pressure in the east and high pressure in the west, the wind will be from the north. When the glass falls low, Prepare for a blow; When it rises high. Let all your kites fly. EFFECT OF WINDS 17 The barometer rises for northerly wind (including from northwest, by the north, to eastward) for dry, or less wet weather, for less wind, or for more than one of these changes — except on a few occasions when rain, hail or snow comes from the northward with strong wind. The barometer falls for southerly wind (including from southeast, by the south, to the westward), for wet weather, for stronger wind or for more than one of these changes — except on a few occasions when moderate wind with rain (or snow) comes from the northward. For change of wind towards northerly directions, a thermometer falls. For change of wind towards southerly directions, a thermometer rises. Moisture or dampness in the air (shown by a hygrometer) increases before rain, fog or dew. GENERAL BAROMETER INDICATIONS. A gradual but steady, rise indicates settled fair weather. A gradual but steady fall indicates un- settled or wet weather. A very slow rise from a low point is usually associated with high winds and dry weather. A rapid rise indicates clear weather with high winds. A very slow fall from a high point is usually connected with wet and unpleasant weather without much wind. A sudden fall indicates a sudden shower or high winds, or both. When the barometer falls considerably without any particular change of weather, you may be certain tliat a violent storm is raging at a distance. 18 WEATHER A stationary barometer indicates a continuance of existing: conditions, but a slight tap on the barometer face will likely move the hand a trifle, indicating whether the tendency is to rise or fall. In the warm months the winds are light and rather variable, and changes in direction have not the same importance as in the colder months. The rain of sum- mer generally occurs in connection with thunder- storms; it will be found that these are most frequent from a certain direction and with the wind in a partic- ular quarter. Beyond the fact that more thunderstorms come from a westerly quarter than from any other direc- tion, little can be said that will be of value in forecast- ing their approach by the direction of the surface winds only. The coming of a thunderstorm can gen- erally be foretold a few hours in advance by the form and movement of the clouds. STORMY WEATHER IN WINTER. The signs of falling weather in the colder months are the formation of a high sheet cloud covering the whole sky, an increase in the temperature and moisture of the air, and the change of the wind to some east- erly quarter. The precise direction that the wind takes, whether northeast, east or southeast, varies for different localities and the direction from which the storm is approaching. In New England, the Middle States and the Ohio Valley, northeasterly winds precede storms that ap- proach from the southwest, and southeasterly winds precede storms that approach by way of the Lake Rapid changes in the barometer indicate early and marked changes in the weather. LOCAL SIGNS 19 Region. On the Pacific coast southeasterly and south- erly winds precede rain storms. In Wyoming and other Northwestern States the heavy snowstorms of winter and spring generally come from the north or northwest with a strong wind from the same direction. The direction of the wind depends very much on the position of traveling storms that pass across the country. In ever_\- locality, there is one direction of cloud motion that betokens bad weather, and another, gen- erally the opposite direction, which portends fine weather, etc. Weather rules relative to red morning and evening sky have been deduced. LOCAL SIGNS. The rules that bad weather is expected when in any given locality the summit of a certain mountain is covered with a cap; that a small, "watery" halo around the moon indicates rain ; that the weather vi^ill continue bad if, when the clouds break up, a second light covering of clouds is seen above them ; that it will be fine weather if, after rainy weather, according to the locality, a certain wind sets in ; that a slow breaking up of the clouds gives promise of fine weath- er, etc., all of these rules have been formulated from long-continued and accurate observation, and are ex- ceedingly well adapted for local weather forecasts from one day to the next. FORECASTING FROM COLOR OF CLOUDS. Experienced observers also know from the color and nature of the clouds whether the prevailing weather will continue or will change and, by these delicate distinctions, generally acquire the reputation of being especially good weather prophets. Should the barometer continue low when the sky becomes clear, expect more rain within 24 hours. The Spider as a Barometer THE spider is a good example of the living barometer. Every twenty-four hours the spider makes some alteration in its web to suit the weather. When a high wind or heavy rain threatens, the spider may be seen taking in sail, shortening the rope fila- ments that sustain the web structure. If the storm is to be unusually severe or of long duration, the ropes are strengthened as well as shortened. On the contrary, when you see the spider running out the slender filaments, it is certain that calm, fine weather has set in, whose duration may be measured by their elongation. When the spider sits quiet and dull in the middle of its web, rain is not far off. If it be active, however, and continues so during a shower, then it will be of brief duration, and sunshine will fol- low. When you see the spiders coming out of the walls more freely than usual, you may be sure that rain is near. THE FROG AS A BAROMETER. A small green frog is found in Germany, which always comes out of the water when cold or wet weather is approaching. These frogs are caught and kept in glass jars furnished with a tiny ladder and half filled with water. The frog weather prophet sits high and dry on the top of his ladder for several hours before a storm, and climbs down to the bottom " Everything is lovely and the goose honks high.' FIRST WEATHER MAPS 21 when the weather is to be fair and clear. Other re- markable weather prophets are leeches. About 1867 a new treatment of weather problems (known as the synoptic method weather charts) was . introduced. Lines were drawn through all places where the barometer read 30 ; others through all reading of 29, etc. These were called "isobars" be- cause they marked out lines of equal pressure. Lines drawn through places where the temperature was equal at the moment were called "isotherms" or lines of equal temperature. Arrows marked velocity and direction of wind. Letters and symbols denoted appearance of sky, amount of clouds and occurrence rain or snow on Synoptic Chart. WHEN THE CHARTS WERE EXAMINED IT WAS FOUND : 1. That in general the configuration of the iso- bars assumed one of seven well defined forms. 2. That, independent of the shape of the iso- bars, the wind always took a definite direction rela- tive to the trend of those lines and the position of the nearest area of low pressure. 3. That the velocity of the wind was always nearly proportionate to the closeness of the isobars. 4. That the weather — that is, the kind of cloud, rain, fog, etc., at any point was related to the shape (not the closeness of the isobars), some shapes en- closing areas of fine, others of bad weather. 5. That the regions thus mapped out were con- stantly shifting their position so that changes of weather were caused by the drifting past of these areas of good or bad weather, just as on a small scale rain falls as a squall drives by. The motion of these areas was found to follow certain lav/s, so that foretelling weather changes in advance became possible. Birds fiy high when the barometer is high — probably because the air is heavier and denser, therefore has more sustaining capacity. 22 WEATHER 6. That sometimes in the temperate zone and habitually in the tropics, rain fell without any ap- preciable change in the isobars, though the wind conformed to the general law of these lines. So far the science rests on observation that such and such wind or weather comes with such a shape of isobars. The same shape of isobars appear all over the world, but their motion and the details of weather are modified by numerous local, diurnal and annual vari- ations which must be studied out. Isobars represent the effect on our barometers of tlie movements of the air above us so that by means of isobars we trace the circulation and eddies of the atmosphere. THE FIRST U. S. WE.VTHER BURE,\U. Although American scientists were the pioneers in discovering the rotary and progressive character of storms and in demonstrating the practicability of weather services, the United States was the fourth countr\' to give legal autonomy to a weather service. Congress authorized the first appropriation of $20,000 to inaugurate a tentative weather service in 1870. Gen. Albert J. Myer, to whom was assigned the chiefship of the new meteorological service, doubt- less had no conception of the future wonderful exten- ^icln of the system that he was then authorized to begin. STORM WARNING ON THE COAST. \\ hether on the .\tlantic, on the Pacific, or on the Lakes, there is either a fidl meteorological observatory i.ir else a storm-warning display-man who attends to If the barometer and thermometer both rise together, it is a very sure sign of coming fine weather. WEATHER BUREAU 23 tlic lighting- of the danger lights on the storm-warning towers at night, to the display of danger flags bv day, and to the distribution of storm-warning messages among vessel masters. This system is so perfect that the Chief of the W eather Bureau, or the forecaster on duty at the Cen- tral Office, can dictate a storm warning and feel cer- tain that inside of one hour a copy of the warning will be in the hands of every vessel master in every port "f material size in the United States, provided that it is his desire that a complete distribution of the warn- ing be made. AnWXXCE RICPORTS OF STORMS REDUCf-: LO.SS 73%. The ]narinc warnings of the service have been so well made that in over six years no protracted storm has reached any point in the United .States without the danger warnings being displayed well in advance. .\s a result of these warnings the loss of life and property has been reduced to a minimum, being doubt- less not more than 25 per cent, of what it would have been without this extensive system. \Mien a marked coUl wave develops in the north- ern plateau of the Rocky Mountains and. by its broad area and great l^arometric pressure, threatens to sweep southward and eastward with its icy blasts, the meteorological stations of the Bureau are ordered to take observations e\'er_\- few hours in the region ini- mediatel}- in advance of the cold area and to telegraph the same to headquarters. FjV this means ever)- phase of the development of the CI lid area i'; carefully watched, and when the dan- ger is great each observatory in the threatened region It is estimated that 80 per cent, to 85 per cent, of weather pre- dictions are successful. 24 WEATHER becomes a distributing center, from which warnings are sent to those who have produce or perishable articles of manufacture that need protection against low temperatures. In England the observed range of the barometer is about 3 inches, whilst in the United States it is 2.7 inches. WEATHER BUREAU 25 The United States Government spends $1,500,000 a year on its Weather Bureau, which is more money than the combined governments of Europe spend. It is not uncommon for the Bureau to distribute 100,000 telegrams and messages inside of the space of one or two hours, so that nearly every city, village and hamlet receives tlie information in time to profit thereby. What this means to the farmer and shipper is well illustrated by the fact that we gathered from those personally interested, statements relative to the sweep of one cold wave, which showed that over $3,400,000 ^vortl^ of property that would have been destroyed by the low temperatures was saved. Even when severe storms are not imminent there is, in addition to the printing of the forecasts in the daily press, a daily distribution of 80,000 telegrams, maps and bulletins, that place the information in the hands of millions whose personal interests are materi- alh- affected by the weather. FINE WORK OF WEATJJER IJUKEAU. Not a single storm has swept across the United States or up or down its coastline within many years that has not been foretold hours, and possibly daj's, in advance by the Weather Bureau. Tlie same applies to cold waves and floods. The time at the di'-posal of the forecast official of the Weather Bureau at the Central Office in Wash- ington City for the purpose of forecasting probable weather changes, cold waves and severe storms is about thirty minutes in the morning and forty at night. It is impossible in this short time to do more than express the character of the anticipated changes The principal maximum barometric pressure occurs before noon and tile principal minimum after noon. 26 WEATHER The barometer atid wind indications o£ the United States are gen- erally summarized in the following table of the U. S- Weather Bureau: Barometer Reduced to Sea j Wind Level. Direction. 30.10 to 30.20 and steady. . I SW. to NW, 30.10 to 30.20 and rising rapidly 30.10 to 30.20 and falling slowly 30.10 to 30.20 and falling rapidly ■ 30.20 and above and sta- tionary 30.20 and above and fall- ing slowly 30.10 to 30.20 and falling slowly 30.10 to 30.20 and falling rapidly 30.10 to 30.20 and falling slowly 30.10 to 30.20 and falling rapidly 30.10 and above and fall- ing slowly SW. to NW. SW. to NW. SW. to NW. SW. to NW. SW. to NW. S. to SE. S. to SE. SE. to NE. SE. to NE. E. to NE. Character of Weather Indicated. 3 0. 1 and above and fall- j ing rapidly i E. to NE. 30 or below and falling slowly 30 or below and falling rapidly 30 or below and rising slotvly 29.80 or below and falling rapidly 29.80 or below and falling rapidly 29.80 or below and rising rapidly SE 1 to NE. SE to NE. S. to S.W. S. to E. E. toN Fair with slight tempera- ture changes for 1 to 2 days. Fair followed within 2 days by warmer and rain. Warmer with rain in 24 to 36 hours. Warmer with rain in 18 to 24 hours. Continued fair with no de- cided temperature change. Slowly rising temperature and fair for two days. Ram within 24 hours. Wind increasing in force with rain within 12 to 24 hours. Rain in 12 to 18 hours. Increasing wmd with rain within 12 hours. In summer, with light winds, rain may not fall for several days. In winter, rain within 24 hours. In summer, rain probably within 12 to 24 hours. In winter, rain or snow, with increasing wind will often set in, when the barometer begins to fall and the wind sets in from the NE. Rain will continue 1 or 2 days. Rain with high wind, fol- lowed within 24 hours by clearing and cooler. Clearing within a few hours and continued fair for several days. Severe storm of wind and rain or snow imminent, followed within 24 hours by clearing and colder. Severe northeast gales and heavy rain or snow, fol- lowed in winter by a cold wave. Clearing and colder. WEATHER MAPS 27 for each state or district east of the Rocky Mountains in any but the most general terms. LOCAL FORECASTING. The local or state forecast official, on the other hand, is concerned with but a single district. He is at liberty to amplify the national forecasts or to put forth a statement of his own, in which the anticipated changes may be given in as much detail as the condi- tions seem to justify. Persons who use the forecasts constantly should cultivate the habit of carefully noting the weather changes in their respective localities, especially the sequences in which such changes occur, for it is only by acquiring a knowledge of local weather signs that they can use government forecasts to the best advan- tage. If the barometer falls gradually for several days during fine weather, expect considerable rain. If it keeps rising while the wet continues, the weather, after a day or two, will probably be fair for some time. Explanation of Weather Map HE U. S. Weather Bureau makes tele- graphic reports of the weather each day at 8 a. ni. and 8 p. m., seventy-fifth meridian time. The reports consist of observations of the barometer and thermometer, the velocity and direction of the wind, amount, kind and direction of movement of clouds, and amount of rain rir snow. weather maps solid lines are drawn through points On th ( isobars) that have the same atmospheric pres sure, a line being drawn for each one- tenth of an inch in the height of the barometer. Dotted lines (isotherms) are drawn through points that have the same atmo- spheric temperature, a line being drawn for each ten degrees of temperature. Heavy dotted lines are some- times used to enclose areas where decided changes in temperature have occurred during the preceding twent)--four hours. The direction of the wind at each station is indicated b_\' an arrow that flies with the wind. The state of the weather — clear, partly cloudy, cloudy, rain or sn(Dw, is indicated by symbols. Shaded areas are used to show areas within which precipita- tion in the form of rain or snow has occurred during the preceding twelve hours. The rapidity of the storm's approach and its intensity will be in- dicated by the rate and amount of the fall in the barometer. HIGHS AND LOWS 29 TABULAR DATA OF WEATHER MAPS. The tabular data give details of maximum and minimum temperature and twenty-four hour temper- ature changes, wind velocities, and amount of precipi- tation during the preceding twent3'-four hours. The text printed on the maps presents forecasts for the state and the station, and summarizes general and special meteorological features that are shown by the lines, symbols and tabulated data. HOW " HIGHS " AND " LOWS " M0\'E. The centers of areas of low barometric pressure, or general storms, are indicated on the map by the word "Low," and the centers of areas of high baro- metric pressure by the word "High" The gen- eral movement of "Lows" and "Highs" in the United States is from west to east, and in their progression they are similar to a series of atmospheric waves, the crests of which are des- ignated by the "Highs" and the troughs by the "Lows." These alter- nating " Highs " and "Lows" have an aver- age easterly movement of about 600 to 700 miles a day. The " Lows " usually move in an easterly, or north of east, di- rection, and the "Highs" in an easterly, or south of east, direction. oljowtTjg •tTiCTta'Se's. lecreise 0^ "Pressure., In the tropics a rapid barometric fall is dangerous because, in a general way, it shows the observer is nearly in path of cyclone. Any fall of more than .02 is dangerous. 30 WEATHER In advance of a "Low" the winds are southerly or easterly, and are, therefore, usually warmer. When the "Low" passes east of a place the wind shifts to westerl)' or northwesterly with lower temperature. The eastward advance of "Lows" is almost invariably |)reccded and attended by precipitation in the form of rain or snow, and their passage is usually followed liy clearing weather. The temperature on a given parallel west of a " Low " may be reasonably looked for on the same parallel to the east when the " Low " has passed, and when the night is clear and there is but little wind frost is likely to occur along the north of an isotherm of 40°. A "Low" is generally followed by a "High," which in turn is followed by another " Low." WHAT ISriTHERMS INDICATE. When isotherms run nearly east and west no de- cided chaiiges in temperature are likely to occur. When isotherms directly west of a place incline from northwest to southeast the temperature will rise ; when from northwest to southwest, the temperature will fall. Southerly to easterly winds prevail west of a nearly north and south line passing through the mid- dle of a "High" and also east of a like line passing through the middle of a "Low." Northerly to westerly winds occur west of a nearly north and south line passing through the middle of a "Low" and also east of a similar line passing through the middle of a "High." An absence of decided and energetic " Lows " and '■ Highs " indicates a continuance of existing weather When the air becomes colder with a low barometer and a south- west wind, squalls from the northeast will certainly follow, and in winter it is nearly always accompanied by snow. WEATHER MAI'S 31 that will continue until later maps show a change, that usually appears in the west. At first glance, weather maps look very con- fusing. The storms of the United States follow, how- ever, year after year a series of tracks, not capricious, but related to each other by very well defined laws. MEAN TRACKS AND AVERAGE DAILY MOVEMENT OF STORMS IN THE UNITED STATES. The chart shows the general result of a study of tracks of storms in the United States. There are two sets of tracks running westerly and easterly, one set over the northwestern boundary, the Lake Region, and the St. Lawrence Valley; the other set over the mid- dle Rocky Mountain districts and the Gulf States. Each of these is double, with one for the "Highs" When the wind sets in from points between east and northeast and the barometer falls steadily, a storm is approaching from the south or southwest. Its center will pass near or to the south or east of the observer within twelve to twenty-four hours, with wind shifting to northeast by way of north. 2:2 WEATHER and one for the "Lows." There are Hnes crossing from one main trade to another showing how storms pass from one to tlie other. The transverse broken Hnes show the average daily movement. On the chart the heavy hnes all be- long to the tracks of the " Highs " and the lighter line? to the " Lows." HOW " HIGHS " TR.W'EL. A "High" appearing on the California coast may cross the mountains near Salt Lake, and then pass di- rectly over the belt of the Gulf States to the Florida coast ; or it may then pass di- rectly over the Florida coast ; or it ma)' move farther northward, cross the Rockv Mountains in the State of Washington, up the Columbia River Valle)', then turn east, and finally reach the Gulf of St. Lawrence. The paths are determined by the laws of the general circulation of the atmosphere and the configuration of the North American Continent. This movement of the "Highs" from the middle Pacific coast to Florida or to the Gulf of St. Lawrence is confined to the sum- mer half of the year — April to September, inclusive. In the winter months, on the other hand, the source of the " Highs " is diiTerent, though they reach the same terminals. TI':i«rS USKIi TN I'-()UI-:C.\STIN(i. "I'^air A\'eathcr" — that is, the absence of rain or suDW, is indicated by several terms. The first of these is the words themselvc^. It lua)' lie used singh' or pre- ceded by the word "generally." "Generally fair," as When the wind sets in from points south and southeast and the barotneter falls steadily, it indicates a storm approaching from the west or northwest. Its center will pass near or north of the observer within twelve to twenty-four hours, with wind shifting to northw^est, by way of southwest and west. FORECASTING TERMS 33 used by the forecast, is less positive than "fair" alone. It signifies that the probability of fair weather over the whole district and for the entire period is not so great as when "fair" alone is used. PARTLY CLOUDY — RAIN — SNOW. "Partly cloudy," is used when the indications favor clouds but no precipitation. "Threatening" is used when the weather will be overcast and gloomy, with the appearance of rain or snow at any moment, yet a measurable amount of precipitation is not antic- ipated. A forecast of "rain" or "snow" may be expressed in various ways. In the late fall, early spring and the winter season it is most commonly indicated by the single word "rain" or "snow," when it is expected that the rain will continue for several hours. In other seasons of the year any one of the following terms, viz., "local rain," "showers," and "thunderstorms," may be used. Forecasts of local rains, showers or thunderstorms indicate that the conditions are favorable for the oc- currence of precipitation in that district. CLEARING. "Clearing" is a word frequently used which car- ries a broader meaning than the word itself signifies, viz., the occurrence of precipitation in the early part of the period ; thus, "Clearing to-night" would indi- cate that rain or snow, whichever might be falling at the beginning of the period, would cease shortly thereafter and that the weather would be clear dur- ing the greater part of the time. No rule can be laid down for forecasting even a single country. The details vary indefinitely and each observer must use his judgment. C. & T. Hand ANY complain that their aneroids are inaccurate if they do not register the same as the readings of the reports is- sued daily by the weather bureaus, which are reduced to " sea level." Suppose a barometer were pur- chased to be used 600 feet above sea level. If the barometric pressure at sea level were 30.4 inches, the barom- eter reading at 600 feet altitude would be 29.8 (6-10 of an inch lower), be- cause the pressure is less at the higher altitude. " The reduction of Barometric Pressure to sea level is one of the most unsatisfactory problems connected with practical meteor- ology."— Frank Waldo, Ph.D. The problem is solved by the C. & T. Patent Alti- tude Adjustment, which consists of an auxiliary hand (copper color) adjustably attached to the pressure hand and moving with it. While the pressure hand shows the actual atmospheric pressure at the altitude at which the aneroid is used, the copper hand may be so adjusted as to show the corresponding sea level pressure. For example, if the aneroid were to be used at Spokane, Washington, (an altitude of 1,910 feet) the In 1643 Torricelli invented the barometer. PRESSURE AT AN ALTITUDE 35 copper hand would be moved to the right a distance of 1.95 inches from the pressure hand, as the pressure of tiie air at this altitude is that much less than at sea level. If the pressure hand then read 28.05, the C. & T. adjustable copper hand would point to 30, which would be the corresponding sea level pressure. 36 WEATHER The illustration shows the hands set for an alti- tude of about 1,825 feet. The following table gives the amount to move the copper hand for various heights above sea level. List of Meteorological Stations — United States. STATION' \ V > " STATION iS" .Abilene. Tex Albany, X. Y Alpena, Mich .\marillo, Tex Astoria, Oreg Atlanta, Ga Atlantic City, N. J Augusta, Ga Baker City, Greg Baltimore, Md Barnegat, N. J Binghamton. N. Y Bismarck, N. Dak Block Island. R. I Boise, Idaho Boston, Mass Breckenridge, Minn Brownsville, Tex Buffalo. N. Y Burlington. Vt Cairo, III Cape Hatteras, N. C... Cape Henry. Va Cape May. N- T Carson Citv. Ncv Cedar City. Utah Cedar Keys. Fla Charlestown, S. C Charlotte, N. C Chattanooga. Tenn Cheyenne. W'yo Chicago, 111 Cienfuegos, Cuba, W. I. Cincinnati, O 1718.0 18.2 586.3 3615.0 18.9 1033.0 8.3 100.4 3441.0 98.0 6.4 862.2 1670.0 16.4 2492.0 —5.0 962.0 37.8 575.8 197.5 269.6 0.0 7.1 6.4 4660.0 5866.4 6.5 9.6 725.0 630.6 6054.0 579.5 15.5 546.9 Cleveland. O Colorado Springs, Col.... Columbia, Mo Columbus. Ohio Concordia, Kans Corpus Christi. Tex Corsicana, Tex Davenport, Iowa Dayton, Wash Deadwood, S. Dak Denisou. Tex Denver, Colo Des Moines, Iowa Detroit. Mich Dodge, Kans Dubuque, Iowa Duluth, Minn Eagle, ,\Iaska Eagle Pass. Tex Eastport. Me Elkins. W. Va El Paso, Tex Erie. Pa Escanaba. Mich Eureka. Cal Evansville, Ind Flagstaff. Ariz Fort Apache. .Ariz Fort Assinaboine, Mont.. Fort Benton. Mont Fort Bridger. Wyo Fort Buford, N. Dak. . . . Fort Canby, Wash Fort Custer, Mont 594.3 5977.0 737.5 709.0 1372.0 0.0 427.5 536.4 1604.0 4543.0 747.8 5183.0 799.0 584.8 2482.0 643.0 601.0 573.0 692.9 5.1 1920.0 3692.0 572.9 593.0 25.7 382.6 6886.0 5000.0 No data 6639.0 192.0 3040.0 METEOROLOGICAL STATIONS 37 Meteorological Stations — Continued. STATION Ind. 1 Ariz. . . Tex. . , Mont. Fort Davis, Tex. Fort Elliott, Tex. Fort Gibson, Fort Grant, Fort Griffin, Fort Keogh, Fort Maginnis, Mont. Fort Sill. Ind. T Fort Smith. Ark Fort Stanton, N. ■Slex. Fort Stockton, Tex... Fort Sully, S. Dak Fort Washakie, Wyo . . Fort Worth, Tex Fresno. Cal. Galveston, Tex Grand Haven, Mich. . . Grand Junction, Colo . Green Bay, Wis Hannibal, Mo Harrisburg, Pa Hatteras, N. C Habana, Cuba, W. I.. Havre, Mont Helena, Mont Huron. S. Dak Idaho Falls. Idaho. ... Independence. Cal. . . . Indianapolis, Ind Tndianoia, Tex Tacksonville, Fla Tupiter, Fla Kalispell, Mont Kansas Citv. Mo Keeler. Cal Keokuk. Iowa Key West, Fla Kitty Hawk. N. C Knoxville. Tenn La Crosse. Wis Lamar, Mo Lander. Wyo Lansing, Mich c V 4> D 0) «*- o .* ^ ri V I 4923.3 536.0 4833.0 1270.0 2367.0 431O.0 415.0 6151.5 3050.0 1593.0 5498.0 600.3 290.0 5.6 581.3 4579.0 587.3 488.1 317.0 0.0 0.0 2483.0 3932.0 1285.0 4714.0 3721.0 708.0 9.0 7.5 1.0 2949.0 721.9 3607.0 481.9 0.0 0.0 806.6 678.5 951.0 5368. 6 827.9 STATION — ^ U V " w > r «-3j I Las Animas, Colo.... Leavenworth, Kans. . Lewiston, Idaho Lexington, Ky Lincoln, Nebr Little Rock, Ark. . . . Los Angeles, CaL , . . Louisville, Ky Lynchburg, Va Mackinaw City, Mich Macon, Ga ^lanchester, N. H... ?>Iarquette, IMich ^lemphis, Tenn Meriden, Miss Miles City, Mont.... Milwaukee, Wis Mobile, Ala Montgomery, Ala. . . . ?\Iontrose, Colo Aloorhead. Minn Morgantown. W. Va. Mt. Tamalpais, Cal f Mt. Washington, N. H Nantucket, Mass Nashville, Tenn Neah. Wash New Haven, Conn. ... New London, Conn..., New Orleans, La Newport, R. I New York, N. Y Norfolk, Va Northfield, Vt North Platte, Nebr Oklahoma, Okla Olympia, Wash Omaha. Nebr Oswego, N. Y Palestine, Tex Parkersburg, W. Va. . Pembina, N. Dak Fensacola, Fla ii 3884.0 737.5 737.8 965.5 1147.0 286.5 255.6 456.5 523.3 582.0 334.0 180.8 627.9 271.3 341.0 2355.0 586.2 0.0 162.0 5796.0 909.0 789.6 2353.3 6300.0 0.0 434.8 0.0 3.0 23.1 8.5 13.6 37.4 —1.4 739.0 2803.0 1195.0 17.0 1040.2 252.0 494.7 616.4 798.4 11.8 38 WEATHER Meteorological Stations — Continued. c oi rtcrt Ph a-^ P^G*i " Si STATION SS^^ STATION SSf^ rt^J i Philadelphia, Pa Phoenix, Ariz Pierre, S. Dak Pike's Peak, Colo Pioche, Nev Pittsburg, Pa Pocatello. Idaho Poplar River, Mont Port Angeles, Wash Port Crescent, Wash Port Eads, La Port Huron, i\Iicll Portland, Me Pertland, Oreg Prescott. .Ariz Pueblo. Colo Puerto Principe, Cuba, W.I I'untarasa. Fla Raleigh. N. C Rapid City, S. Dak Red Blutt, Cal Richmond. Va Rio Grande City, Tex Rochester, N. Y Roseberg. Oreg .Sacramento, Cal St. Louis, Mo St. Michael's, Alaska St. Paul, Minn St. Vincent, Minn Salt Lake City, Utah San Antonio, Tex San Diego, Cal Sandusky, Ohio Sandy Hook, N. .t. ...... . San Tuan, Porto Rico, W.I .San Francisco, Cal 1084.0 1441.4 14107.7 6100.0 697.0 4466.9 1955.0 11.3 8.5 4.0 581.3 47.2 8.2 5320.0 4656.0 324.7 2.0 .317.0 3175.0 306.0 164.2 200.0 509.8 482.0 2.0 412.7 23.3 693.7 798.4 4268.0 683.0 5.8 572.9 9.2 0.0 8.0j tSan Luis Obispo, Cal... j Santa Fe, N. Mex Santiago, Cuba. W. I... Sault Ste. Marie, Mich. Savannah, Ga Seattle, Wash .Shreveport, La Siou.x City, Iowa Sitka, Alaska Southport. N. C Spokane, Wash Springfield, 111 Springfield, Mass Springfield, Mo Tacoma, Wash Tampa. Fla Tatoosh Island, Wash.. Thatchers Island. Mass. Titusville, Fla Toledo, Ohio . . . Tucson, Ariz L'matilla, Oreg Unalaska, Alaska Valentine, Nebr Vicksburg, Miss Virginia City, Mont.... Visalia, Cal Walla Walla, Wash Washington, D. C Wichita. Kans Williston, N. Dak Wilmington, N. C Winnemucca, Nev Woods Hole, Mass Yankton. S. Dak Yuma, .\riz 240.0 6954.0 0.0 607.3 41.7 22.3 187.2 1107.0 62.9 14.0 1010.0 600.2 70.0 1348.0 31.0 —1.1 162.0 53.0 1.0 572.8 2389.0 297.0 8.0 2581.0 223.2 5824.0 325.1 923.0 91.2 1300.0 1854.0 31.9 4335.0 4.0 1197.3 140.5 DIRECTIONS FOR ANEROID Table No. 2. 39 Table No. 2 gives the fraction of an inch, in which the red hand should be moved to the right upon the dial for each successive thousand feet of elevation at which the Barometer will be used above sea level. Above Sea Level. Move Hand to the Right. Above Sea Level. Move Copper Hand to the Right. 500 feet 0.5 scale inch 1,000 •■ 1.1 " 1,500 •■ 1.6 " 2,000 " 2.1 " 2,S00 " 2.6 " 3,000 " 3.1 " 3,500 " 3.6 " 4,000 feet 4,500 o.OOfl 5,500 6,000 6,500 7,000 4.1 scale inches 4.6 3.0 5.5 6.0 6.5 7.0 Cyclones C^■CLONES LOW. T times the barometric pressure over a part of a country is much below the average, 'sometimes as low as 29 inches or even less. In such cases the pressure increases in wid- ening circles for a distance of several hun- dred miles from the place of lowest pres- sure. .\ s\stcni of isobars of this kind is called a " Cyclone." Tt is usually accom- panied by rain and high winds in the coun- Iry over which it lies. The " Lows " are sometimes called storms. The center of the smallest isobar is called the storm center. When the shape of the isobar representing an area of low pressure are not rounding nearly circular, the area is called simply a " Low " or a " Depression." CAUSES 01- CYCLONES OR STORMS. Cyclones are due primarily to the unequal heating and moisture, or cooling and drying, of the air over large regions of the earth's surface, disturbing the level of the surfaces of equal density. This results in a convectional ascensional movement of the lighter air near the ground and the coming down of heavier air from above to restore the equilibrium. The light air moves spirally inward and upward, and at a great- er height flows outward to the sides. This flow is similar to that of water from a basin through a hole .02 fall per hour is considered low; .05, high. EFFECT OF CLOUDS 41 in the bottom. The motion from opposite sides gives rise to the rotation. When the upward convection extends to a height at which the temperature is lowered by dynamic cool- ing below the temperature of the dew-point of the air, there is a condensation and cloud formation. When this occurs, the initial gyratory impulse of the air be- comes of secondary consequence. The principal part in maintaining and extending the ascending motion is taken b)' the latent heat set free from the vapor. The cloud canopy in the daytime also increases the tendency of the air to ascend by transferring the point of application of the sun's heat from the ground to the top surface of the clouds at a height in the air. DRY CYCLONE. Convectional ascending motion in the air is going on at all times during the day, but for the most part is not sufficient to carry the air high enough to pro- duce any great amount of condensation, sometimes on account of the feebleness of the ascensional force, and again because of the dryness of the air requiring as- cent to a very great height to reduce it to the dew- point. This condition sometimes produces a dry cy- clone of feeble action, with cloud formation only, and no rain. The decrease of pressure in a cyclone pro- duced by rainfall alone is very slight. The centrifugal force developed by the gyration and the defecting in- fluence of the earth's rotation on the currents are the main causes of the production of low pressure at the centre of a cyclone. THE B.XROMETER IN RAir.RO.ADING. Familiarity with a barometer and the ability to interpret its meaning probably had as much to do as On only a few occasions in any year will .10 be exceeded, though ,20 has been recorded. 42 WEATHER any single thing with the rapid rise of R. H. Aish- ton in the service of the Northwestern Railway. Few people in the operating department of a railroad would regard a barometer as a valuable adjunct to the achievement of the best results, and hence to success and promotion. "What does Uncle Sam hire a weather man for?" most men would say, "and why not ask him if you want to know what the weather is going to be?" Early in his career Mr. Aishton figured it out that the weather had a great deal to do with the opera- tion of railroads, and so he determined to be his own weather man. Now that he has risen to the position of general manager he keeps the best barometer that money can buy hanging on the wall close to his desk. When Mr. Aishton was superintendent of the Chi- cago division of the road he and his barometer saved the company enough money to pay his salarj' for the next decade and have a surplus. It came about in this way : Traffic was so heavy that it was making the operating men work day and night to prevent freight trains from piling onto one another and causing all passenger trains to be annulled. During those anxious days and nights the superintendent watched his bar- ometer much as a mouse watches a cat. Its slightest variation did not escape his notice. One day he saw that the little needle under the glass was doing some unusually funny stunts. After two days of this kind of performance Aish- ton called up the weather man and asked him what he made out of the gyrations'. Mr. J. H. Belville, of the Royal Observatory, Greenwich, says of the Aneroid: "Its movements are always consistent. It was a de- lightful companion and highly useful, its indications preventing many an excursion that would have ended in disappointment." A BAROMETER STORY 43 "I can't see any heavy storm headed this way," declared the weather prophet, "but I don't know just what to make of it." " I don't believe you're looking straight," muttered Aishton to himself as he rang off, "if you can't see trouble ahead." The superintendent studied his barometer again for a few minutes and then, wheeling quickly around to his desk, he exclaimed : "I'll take a chance and back my own judgment, anyway." Ringing his bell he gave his messenger an order, and dismissed the subject from his mind. "And the next day it snowed," as the expression has it, and it kept on snowing for three days and three nights. It was the worst snowstorm Chicago had experienced for many years. Traffic at the Chicago terminals was completely paralyzed — that is, on every railroad except the Northwestern. All the other railroads frantically sought laborers to shovel the snow off the tracks and out of the freight yards that freight might be moved. The quest of the railroads was in vain. As the result of Aishton's order 2,000 men had been secured two days previous to the great storm and the labor market was very short. To this day there are few who know the secret of the great operating coup. A few operating men, however, learned the facts, and now Air. Aishton is not the only Chicago operating offi- cial who makes a careful study of his barometer every morning before he opens his desk. ADJUSTMENT NECESS.'XRY. An aneroid barometer may be out of adjustment, In Saint Petersburg and Iceland it is 3.5 inches, whilst at Chris- tiansburg, near the equator, the entire range was only 0.47 Inches, cov- ering five years. 44 WEATHER so far as not agreeing with the reading of a mercurial barometer, and still give accurate measurements of the amount of change in atmospheric pressure. It is more satisfactory to the observer, however, if his in- strument be compared with a Standard Mercurial Barometer. If they do not agree, the aneroid may be adjusted by turning the small adjusting screw until the indi- cating hand on the dial coincides with the height of the mercury column. The finest quality barometers require a slight adjustment at the end of say six months and then about once in nine months. .-Vfter a time they become so nearly permanently accurate that they require no re-setting. The ordinary grade of instruments natur- ally require more frequent adjustment. The most progressive dealers have an Aneroid Testing Outfit but a fairly accurate comparison can l)e made without it. COMPENS.ATION (IF -VNEKOIDS. All tine quality aneroids are compensated to coun- teract the expansion and contraction of the metals, which alters the leverage of the mechanicism, mak- ing the indications very inaccurate. In compensating a barometer, it is necessary to make the lever "F" (See cut page 59) of a compos- ite bar of two metals (steel and brass), the quantity of each being altered until it is correctly "'compensat- ed" for any change in temperature. This avoids the ne- First rise after low. Foretells stronger blow; Long foretold, long last. Short notice, soon past. FOR MARINE USE 45 cessity of making allowances for temperature, which is necessary in reading a mercurial barometer. Some manufacturers attempt to compensate for temperature by leaving a small quantity of air in the vacuum chamber. When heated this increases its pressure upward and tends to offset the weakening effect upon the springs. ANEROID FOR M.\RINE USE. The Aneroid Barometer is the best instrument that can be devised for marine use, not only on account of its extreme sensitiveness, but also because it is not affected by the motion of the vessel. It is now recog- nized as a necessity for the mariner and is made in many compact forms for use in yachts An important testimonial for their nm e.xcellence for mariners was given in the generous action of the Life Boat Insti- tution of Great Britain, when, in order to promote its use and prevent the loss of life amongst this fine class of fisher- men, they offered to provide the master of any fishing smack with an aneroid at half price. SYMPIESOMETER. A barometer in which the atmo- spheric pressure is exerted directly on a short column of oil or similar liquid, causing compression of a portion of air or gas enclosed in ihe tube above the liquid ; highly sensitive, but very liable ment and great inaccuracies. tf ft It u to derange- Rainbow in morning, Shepherds take warning; Rainbow at night, Shepherds' delight. 46 WEATHER WATCH AND POCKET ANEROIDS. For the tourist engineer and surveyor, the Aneroid Barometer is not only very interesting but also indis- pensable, as it measures with great accuracy the heiglit of hills, mountains and gradients. There are many forms in use, but the regular watch or pocket style is the most popular. Some are fitted with compasses on the back, but the magnetic influ- ence of the needle has been known to influence the steel parts of the Ijarometer, causing in- correct readings, while the compass on the back of the aneroid is prac- tically useless imless de- tached, owing to the magnetic attraction of the steel parts. There are many styles with md without thermometer on the dial. l.ij" dial reading to 15,000 divisions. Watch and pocket barometers are made with ti.xed and revolving altitude scales. They are made to accurately register alti- tudes up to 20,000 feet. Those which register to 3,000 feet have the finest divisions, the value of each A red morn, that ever yet betoken Wreck to ttie seamen, tempest to the field. Sorrow to shepherd, woe unto the birds, Gust and foul flaws to herdmen and herds. POCKET ANEROIDS 47 being but 10 feet. By sub-dividing, a careful observer can take very close readings. As the value of the altitude scale decreases, as the lYi" dial reading to 16,000' in 100' divisions. pressure lessens, the "0" of the altitude scale should always be exactly opposite 31 inches on the barometer dial before taking an altitude reading. ' Mackerel sky, Twelve hours dry.' 48 WEATHER For example, suppose the aneroid indicated a pressure of 27 inches. If we ascend a hill and the hand (due to decreasing pressure) moves to 22 inches, the correct method of determining the difference in altitude, would be as follows : Ap- proximately the value of 27 inches (with the "0" feet at 31 inches) is 3,750 feet, while the value of 22 inches, under the same conditions, is 9,350 feet. 9,350' 3,750' yi.ooo — JQSOO - — J 0.0 CO — _ 9.500 - 9,000 8..S0O - - SpoO — — /5K7 - ~ 7000 — 0£cc - _ <>.ooo — jyoo - so 00 J^rSOC _ 4,\ «CVV-, cl)ffTn>«01 T' lEv«i ^.i.a.l:o.inia"^v5y TTuwrmtnt ij^cTuT^lxTi T> $c-n-^ una lio riiftt or lo-Jt-- vacoj™* to sSiJit fon o . cb.Tt j(oi.ui..lt. tV-*J p"! ojJcTlfli LT^a ,>.-. 6 Co./i,ttrpon» A Barogram is the record made by a Barograph. o2 WEATHER weekj, and sub-divided to spaces representing two hours each, it is possible to tell at what time of any (\a\, atmospheric conditions undergo a change. While the ranges of charts vary, the one universally used shows pressure from 28" to 31", the value uf each division on the chart being- .05 inches. .\11J L'STMENT OF B.-\ROGRArHS. Barographs should he adjusted (to read with a standard barometer) Ijy turning the small milled head .-^cre\\■, directly over the bridge spanning the vacuums. An evening grey, •And a morning red; Will send the shepherd Wet to bed. RECORDING BAROMETERS 63 Tue^Jny The pen will rise or fall, dependent on the direction the screw is turned. The compensation for temperature is accomplished by leaving a sufficient quantity of air (ascertained by experiment when instrument is made) in one of the vacuum chambers so that the tendency of the baro- meter to register too low (on account of the weak- ening of the springs, the expansion of the levers and other parts) due to a rise in temperature, is counter- acted by the increased pressure of air in the vacuum cell. The instrument should, however, be kept in as uniform a temperature as possible. With a rising recording baro- meter the trace of the pen is convex for a decreasing rate and concave for an increasing one. The reverse is true of a falling barometer. If fall is steady the line will be straight diagonally. This cut illustrates one advantage of the baro- graph. Two observations of an aneroid were made (at 10 p. m. and 8 a. m., re- spectively) both showing a reading of 30 in., which would indicate a "station- ary" barometer with a con- tinuance of present weath- er. A glance at the baro- graph record shows a rapid fall and rise between 10 p. m. and 8 a. m., which Conv Concave. In winter heavy rain is indicated by a decrease of pressure and an increase in temperature. 64 WEATHER indicates a short but severe storm due at about 9 a. m. Speaking of a certain " delicate " barogram, Hon. Ralph Abercromby, F. R. M. S. London, says : " A case of this sort shows more than any other, the superior vahie of a continuous trace over an intermittent barograph, for though the latter permits the tabulation of hourly values, they entirely lose all chance of following these minute alterations of pressure which are often accompanied by great changes of weather." barograph is valuable in the measurement of altitude as it dispenses with the necessit}- of keeping an observer at the base of the mountain, the baro- graph aiifotiiatically yecordiiig all dif- ferences in pressure and timing them. See p. 54-55.) ALTO, r.AROGRAPlI. A new style of barograph, known as the " Altitude Barograph," has re- cently been perfected. In construc- tion, it is exactly similar to the regu- lar t_\-])e of instrument, differing only in the chart, which is higher and divided to read for elevations instead of inches of pressure. The divisions on the chart are of 50 feet values, enabling a careful ob- server to take readings of 25 feet. The range is 6.000 feet. This instrument is very interesting to travellers because it records the Franklin ascribed the dry fog met with in London to the large quantities of coal tar and paraffine vapor sent into the atmosphere, which condense on the particles of fog. preventing their evaporation. ALTITUDE BAROGRAPH 65 altitude, giving exact time and day any elevation was reached. In a trip over the mountains it will tell the altitude of the summit and at what time reached, (providing Barograph of course, it did not exceed 6,000 feet) and the time of every 25 feet of ascent. On the descent it will of course work the reverse way. USE OF RAROGR.-\PH.S .\T .SI-;.\. Barographs arc invaluable for mariners as they are not affected by the roll and motion of a vessel at sea. Here it is important to know not only the amount of rise or fall but also whether rapid or slo«-, as winds and seas depend upon these conditions. In all well appointed vessels it is now recognized as a necessity. An interesting attachment is made for recording barometers, in the shape of an auxiliary dial (p. 66). No dew after a hot day foretells rain. 60 ^^'EATHER Its hand is actuated by the same movement as the liarograph and therefore registers the same as the pen upon the chart. Instead of complicating the baro- graph the advantage to the lay user is obvious as the present barometer readings are more readily deter- mined bv reference to the dial. D.ir with .\uxiliar\- Dial. Thermograph or Recording Thermometer Experiments have been made with many different t\-pes of recording thermometers, some depending upon a metallic spirit tube for their movement ; others The temperature of the sun is 14.072 degrees F. THERMOGRAPH 67 on a bi-metallic bar. As the latter style is more accurate, durable and constant in its action, it has been adopted as a standard by the best makers. DEFECTS OF SPIRIT TUBE THERMOGRAPHS. In the "spirit tube" thermograph the constant ex- posure to the air corrodes the metal, causing it to be- ' come more or less porous and leaky, making the in- strument highly inaccurate. The mechanism also necessitates a series of levers, magnifying the move- ment of the tube. The "pins" which fasten these levers often become rusted causing the instrument to register even more inaccurately. Thermograph. The illustration shows the metallic coil of the thermo- graph fitted to the back " bridge " of the instrument, wire netting or perforated glass at the end of the case enabling the air to circulate freely around the coil. Thermogram is the record made by a Thermograph. 68 WEATHER The thermograph now most generally used has a spiral coil of two different metals (brazed together) with the pen arm fixed directly to the coil. The ex- pansion and contraction of the spiral coil causes the pen arm to move up and down, recording the tempera- ture on the chart. USE OF THERMOGRAPHS. Accurate thermographs are an absolute necessity in ship's stores, refrigerators, ice plants, railroads and fruit vans, as in such places the question is not so much "What is the temperature?" as "What has been the temperature?" Where a uniform temperature of say 40° is ne- cessary, the thermometer at the time of inspection may show 40° but it does not tell if the temperature has been above or below 40° in the past two, four, six or eight hours. The thermograph keeps a time record of all fluctuations in temperature, any altera- tion on the chart being easily detected. Barogram plus Thermogram plus Anemogram equals Metogram. THERMOGRAPH 69 Combined Thermograph and Barograph. COMBINED THERMOGRAPH AND BAROGRAPH. A recent improvement has been introduced into recording instruments by combining the barograph and thermograph in the same instrument. The records are given on the same chart but in different colored inks to prevent confusion. 70 WEATHER ^!. .djtJrf^:. ^ J. 1738. 'r>^^ SOME OBSERAVTIONS R E r L E C T I O N 1 COKSTRb'CTJON AND GRjrU.lTIOW THERMOMETERS. WE c-iniiLrL ciii)Ur'!i cominem! and acjmlt-r tl.,-; cxolienc imxncion cf Thrn-^-i:^- iLi-., wkcrtby H-c .-r. ci.bkd to mck^ fi/me j'jilpemciii of Oi^- varmj. '^-;j:ri;es of heat in t.ot1i::£. !l h net ojt hti^r •(< . i [Tiftnt to lietct- liiint; to whom wf o-ac thst roil- ^n I tifcful .lif- .-nvtty; ,v!.tth.c to S-.naorio, -j li t^iX-, 'o Fj- ihtT Pjul, or to rr'Lbt^l . tor I titfl i> ^tcnV-.i to l.SS". Above, we show a halftone of the title page of a book on Thermometry written in 1738 by Bernardinus Teleius. There are some very interesting facts in this old book, which, if space permitted, we would like to re- produce. In certain locations in the interior of Australia, the temperature frequently drops 60 to 70 degrees in a few hours. AN OLD THERMOMETER BOOK 71 OLD IDEAS OF POINTING TUBES. At one time, the bright minds of the country de- cided that the freezing point of liquors varied to such an extent that it could not be used as a test point, sug- gesting taking the temperature " In a cave cut straight into the bottom of a cliff fronting the sea to the depth of 130 feet with 80 feet of earth above it." Speaking of this, our author says : " But with Dr. Hale's leave, this degree of -temperature I do not think a very convenient term for universal construction of thermom- eters. Everybody cannot go to Mr. Boyle's grotto; and it is but few who can have an op- portunity of making observations and adjust- ing thermometers in the cave of the ' Parisiam Observatory.' " Other quotations are: " Fahrenheit actually found that water was capable of a greater or less degree of heat in boiling, according to the greater or less weight of the atmosphere. " And some have suspected that water freezes at different degrees of heat in differ- ent seasons, countries and climates. And Dr. Cyrilli's observations would seem to confirm it. At Naples he found water to freeze when his thermometer was 10 degrees above the freezing point, as it had been constructed in England (while tjiis difference in the freezing point was supposed to be due to ' some saline additional mixture from the air, it was prob- ably due to inaccurate thermometer')." He says of Sir Isaac Newton : " He carried everything he meddled with beyond what anybody had done before him and generally with a greater than ordinary ex- actness and precision." A change of 60 degrees F. in 24 hours has been observed in the United States but twice from 1880 to 1890. 72 WEATHER He then goes on speaking of the scale laid out by Newton having test points at freezing water, the heat of the human body, boiling water and melting tin, saying : " I wish the world would have received this or any other determined scale for adjusting their thermometers, but I suppose they might be apprehensive of some inconveniences in this scheme." Speaking of the bulbs of Thermometers which were then made about 4 inches in diameter, he says: " I find them to quabrate very ill together, just I suppose from that cause of the different sizes of their bulbs * * * small bulbs and small tubes are (notwithstanding the imaginary faults and difficulties stated against them by Mr. De Reaumur") vastly more convenient and may be constructed sufficiently accurate." Speaking of the faults of various liquids to be used in Thermometers, he says : " We have, it seems, nothing left but quick- silver. This is a very movable and ticklish fluid; it both heats and cools faster than any liquor we know of or have had occasion to try. " It is said that they were first contrived by that curious mathematician, Olaus Roemer. Mr. Fahrenheit in Amsterdam and other workmen in that country manufactured very many of them, and that in a portable and mighty convenient form for many purposes, making them very final and enclosing the tube in another glass hermetically sealed." The lowest temperature in United States — 63 degrees below zero — Poplar River, Mont., January, 1895, THERMOMETERS IN 1738 73 CALIBRATION. " Indeed in all this we have supposed the bore of the tube to be perfectly cylindrical, which cannot always be obtained. But though it be tapering or somewhat unequal, it is easy to manage the matter, by making a small portion of the quicksilver, as much, for ex- ample, as fills up a half, or, if you please, a whole inch, slide backward and for- ward in the tube: and by this means to find the proportions of all its inequalities and from them to adjust your division to a scale of the most perfect equality." Of a method of a scientist in marking as a test point the heat of a summer day, he says : " This, indeed, is a very incongruous way of graduating thermometers, as the great heat of the summer sun is such an indefinite de- gree of heat in different days, years, climates, etc." St. Andrews, 1738-'39. An ESSAY towards a NATURAL AND EXPERIMENTAL HISTORY of the Various Degrees of HEAT in BODIES. 1. Of the way of computing the diflferent degrees of heat. Many of the ancients had strange notions of the nature of heat. They supposed it in diflferent subjects to differ in kind as well as quantity. They talked very magnificently of the Celestial Heat, as differing much The highest temperature registered in the United States was at Death Valley, Cal., June 30th, July 1st and 2nd, 1891, when thermom- eter reached 122 degrees F., X, 74 WEATHER in its nature from the heats commonly produced on our earth. And these, too, they thought to be of quite different natures in the diflEerent bodies wherein they are lodged. The heat of the fire or of hot water, or of fermenting substances, they thought of a lower kind, and altogether distinct from the heat of animals. And this, too, they distinguished into natural and preter- natural, or morbid, as sorts of heat quite different from one another. And those, too, they reckoned of different natures in the different species of animals. Doctrines and ways of speaking of this sort, set up by their peripatetic school, and too much adopted by Galen and the Physicians after him, continued long in the world ; and were also countenanced by the chem- ists, these philosophi per ignem, who professed and valued themselves on a more than ordinary knowledge of the secrets and operations of heat. EXCESSIVE HEAT IN YE OLDE TYME. Much has been said of the scorching and intoler- able heat of the sun in the torrid zone. We have many strange stories of extraordinary summer heats, as great tracts of land, houses, etc., set on fire, stones heated so as to melt lead, etc. These indeed seem ex- travagant. But the German annals preserve the mem- ory of an excessively hot summer in 1230, when they roasted their eggs in the sand heated by the sun. And I have been told that in Egypt, by no means the hottest country in the world, they can often on the tops of their houses roast their eggs at the sun. And to harden the white of an egg I find the heat of about gr. 156 to be necessary. In the year 1705 the summer was very warm. At Montpelier one day the sun was so hot as to raise the quicksilver in M. Amontons's Thermometer to the mark of boiling water itself, which is our gr. 212. Heat tf*- ^ E are always talking about our many W advantages, but few of us realize that we have in our climate our greatest ad- vantage. In the cold wave which so often sweeps across the land, sending »the thermometer tumbling thirty de- grees in almost as many minutes, we have an asset of pricless value. The wave acts as a tonic, but, unlike any other tonic, it carries no reaction. No other land has cold waves like ours. The cold wave is born usually miles over the Rocky Mountain plateau. Sud- denly a mass of bitterly cold air will tumble down upon Montana. It rushes down as though poured through a large funnel. When it reaches the earth, it spreads over the Mississippi Valley and then over the Atlantic States, covering them like a blanket. Scattering the foul, logy, breath- soaked atmosphere in our towns, it puts ginger into the air. SOURCE OF HEAT. Heat is received either from the sun (solar heat) or from the earth (terrestrial heat). Considerably be- low the surface of the earth, the influence of the ter- restrial heat is more strongly felt ; while at the earth's The temperatures of a body must not be confounded with the quantity of heat it possesses. A body may have a high temperature and yet have a very small quantity of heat, or vice versa. 76 WEATHER. surface, heat from the sun is more noticeable. Solar heat is transmitted in every direction radially (straight out, like spokes from the hub of a wheel). Usually (not always) the temperature of the air decreases with the altitude above the earth's surface. Observations have, however, produced a great variety of results, so that the matter is at present not definitely settled. The diminution is considered slower in the case of moist than of dry air. THE THERMOMETER. It has taken many centuries to perfect that simple yet wonderful instrument — the ther- mometer — used for the measurement of temperature. Many people are credited with its invention; Drebbel (a Holland- er) being referred to more than any, but to Galileo Galilali the laurels are hand- ed. It seems that about 1592 he "in- vented" the thermometer described as "a glass containing air and water to indi- cate changes and differences in tempera- ture." This was perfected more or less by the Grand Duke of Tuscany, Ferdi- nand the Second, about 1610. They seem to have been made first at the glass works in Murano (near Venice) of a glass tube, the width of a finger, to which was fixed a bulb with a capacity of three or four ordinary drinking glasses. Fahrenheit may be said to have made one of the greatest discoveries in relation to the subject when he learned that water always freezes at the same tem- perature. (See footnote). Increasing the pressure on water 1 atmosphere (14.7 lbs.) lowers the freezing point .0075 C. 1502 FIRST THERMOMETERS 77 In 1714 he devised a scale for which the fixed points were determined by the ordinary heat of a healthy human body and the degree of cold generated by a mixture of ice and salammoniac or common salt. The thermometer on which this scale was used was followed, a few years later, by a mercurial one con- structed with regard to a belief, then held by certain learned men, that water would always boil at the same temperature; and it was by means of experiments made with this instrument that Fahrenheit was able to declare that atmospheric pressure governs the boil- ing point of water. THE FIRST THERMOMETER WITH SEALED TUBE. About 1650, a most important and radical change was made by Ferdinand the Second, who manufactured a thermometer tube of the present form, filling it to a certain height with colored alcohol. He then closed the tube, hermetically sealed it and graduated the degrees upon the stem of the tube. This was after Torricelli had invented the barometer or demonstrated the weight of the air, and was the first thermometer made to work independent of the atmos- pheric pressure. The thermometers of Florence became famous throughout Europe, as did Torri- celli's barometer and a hygrometer invented by Ferdinand the Second. A number of meteorological stations were established by The highest known average monthly temperature ever observed is that of 102 degrees F. for July at Death Valley, California. The low- est is — 60 degrees F. for January at Werchojansk, Siberia. 78 WEATHER. him in Florence, Pisa, Bologna, Milan, Warsaw, Par- ma and Innsbruck, where observations were made with these instruments several times daily. Robert Hooke and Hon. Robert Boyle, of the " Royal Society in London," were the first to realize the necessity of having a standard scale. About 1662, Hooke, placing his instrument in freezing dis- tilled water, marked " zero " at the top of the column of spirit after immersion of the bulb. Soon after, he suggested that the second point should be the boil- ing point of water, but this does not seem to have been adopted at that time. SUGGESTED " TEST " POINTS. Delance suggested that the freezing point of water should be marked "cold" (—10°), the melting point of butter " hot " ( 10 ° ) and the space mid- way between "temperate" (0°) with ten divisions between each. FIRST USE OF MERCURY IN THERMOMETERS. Athanasius Kircher was the first to use mercury in thermometers, about 1641, but Fahrenheit was the first to construct mercury thermometers with re- liable scales (1714). His scale (with Centigrade and Reamur) is used as a standard throughout the world to this day. 16-16 Delance once remarked that mometers," curious people use mercury in ther- SCALES ON THERMOMETERS 79 ANCIENT SCALES ON THERMOMETERS. Thermometers for special uses were first manufac- tured in 1726 by Fowler, of London, mostly for use in hothouses. They ranged in length from one to four feet, being graduated only to 90°. THE REAMUR SCALE. Reamur, a Frenchman, (about 1730) brought to public notice his new scale, in which he made " 0° " the freezing point of water and 80° the boiling point, but his scale has never enjoyed such public favor as Fahrenheit's. THE CELSIUS SCALE. Anders Celsius, in 1742, proposed a new scale with the boiling point of water at " 0° " and with melting ice at 100°. The Centi- grade scale is the result, but the two points were re- versed by Christin ( Lyons, France ) in 1743. From this time on, as science has advanced, the ther- mometer has been perfected into a most scientific in- strument. Inspecting the Canes. When the sanie amount of heat falls on land and water surfaces, the temperature of the land is raised nearly twice as many degrees as the water. 80 WEATHER TO CONVERT ONE SCALE TO ANOTHER. To convert Centigrade degrees into degrees of Fahrenheit, multiply by 9, divide the product by 5 and add 32. To convert Fahrenheit degrees into degrees of Centigrade subtract 32, multiply by 5 and divide by 9. To convert Reaumur degrees into degrees of Fah- renheit, multiply by 9, divide by 4 and add 32. To convert Fahrenheit degrees into degrees of Reaumur, subtract 32, multiply by 4 and divide by 9. To convert Reaumur degrees into degrees of Cen- tigrade, multiply by 5 and divide by 4. To convert Centigrade degrees into degrees of Reaumur, multiply by 4 and divide by 5. Water freezes at 32° Water boils at 212° Water freezes at 0° Water boils at 80° f^ Water freezes at 0° ^' Water boils at 100° R. F. Graduating scales. THE MAKING OF THERMOMETERS. Everyone is familiar with the thermometer for register- ing air pressure, but few re- alize how much care must be ex- ercised in its manufacture. Th e glass tubes are drawn to great lengths, frequently exceeding 300 feet. These lengths are cut into pieces ("canes") four feet long. Each Greatest natural cold recorded in Arctic expeditions, — 73.66 F. THERMOMETER MANUFACTURE 81 piece is carefully examined, when all except four or five nearly perfect canes are destroyed because of de- fects. The more partic- ular the manufacturer, the greater the cost of the fin- ished thermometers. THE BORE OF TUBE. In some thermometers the bore is much finer than the diameter of a hair, the capacity of the bulb being 1000 times as great as the capacity of the bore. The bore looks much larger thao it is on account Examining the Bore. of the magnifying lens front. The " canes " are . cut twice the length of ther- mometer tubes desired. One of the pieces is held in the flame of a blow pipe at the point where it is to be severed. When suffi- ciently heated, it is with- drawn and pulled apart. Toining the Bulb The average temperature of the air in England is about 50 de- grees. The average temperature of the air in the United States is about 52.4 degrees. 82 WEATHER Blowing the Bulb. making two tubes, each sealed at one end. The sealed end is heated, being withdrawn from the flame at the proper moment, when a bulb is formed by blowing through the open end of the bulb. The bulb is turned round and round in the flame and (by blow- ing at the open end of the tube) is gradually in- creased in size. The pro- cess is repeated until the bulb is the exact size de- sired. Glass is such a poor conductor of heat that the workman can hold the tube within about an inch of the red-hot portion. BLOWING THE BULB. Blowing the bulb is a very delicate operation, as on its exactness depends the control of the rise of Filling Tubes. The same weight of water requires about 32 times as much heat as mercury to produce the same elevation of temperature. THERMOMETER BULB 83 the mercury in the tiny bore. For an open range ther- mometer a small column and a large bulb is necessary, while for a close range instrument, a large column and a small bulb will produce the slight movement required. Melting ice test. In another department, the bulb is heated in the flame of a Bunsen burner to expand the air it contains The tube is then inverted in a vessel containing mer- cury. As the expanded air in the bulb cools, it con- tracts, forming a partial vacuum, which draws the mercury into the tube. Several repetitions of this process finally fill the bulb and tube to the proper point. ROASTING THE TUBES. The filled tubes are then " roasted " to expel every particle of moisture. This is done by placing them in heated sand for the necessary time, depending on the amount of humidity in the air when tubes are made. The bulb is then held over a gas flame until the mercury in it boils, thus driving out the balance of A white frost never lasts more than three days; a long frost is a black frost. 84 WEATHER the air, when the tube is again thrust into the vessel of mercury and the bulb completely filled. As soon as the bulb has cooled thoroughly it is plunged in cracked ice to drive the mercury to a low point, where it will be out of the way. The flame is blown across the tube at a point near the top where it is desired to cut it off, and the tube is brought to a red heat and is drawn out until it is very thin, but still contains a minute hole at the center. The bulb is once more heated until the mercury completely fills the tube and a small portion of it escapes, all the air originally in the tube and bulb being thus displaced. The top is then securely sealed and a " hook " drawn by which to secure the tube to the back of the scale. After being " pointed," the tube is laid on a blank strip of metal, which is to become the scale for this particular tube, and the test points are transferred to the blank scale. The graduating machine can then be set to cut the space between any two of the points into exact sub-divisions, varying from a few to a hun- dred to the inch. WHY SCALES ARE NUMBERED. Each scale is then given a serial number, corre- sponding to the number of the particular tube to which it belongs. ^ In the manufacturing process they now separate, coming together (when completed) to be assembled. Seldom, if ever, will two thermometer tubes fit one scale. For example, tube No. 10,000 must be mounted on scale No. 10,000 or the finished thermometer would be inaccurate. After his return from the Arctic regions. Sir Leopold McClintock said : " The atmosphere changes were indicated first by the Aneroid, next by the Sympiesometer and last by the mercurial barometer.*' CALIBRATING 85 When a tube is broken in the course of manufac- ture, the corresponding scale must be " scrapped," as it would fit no other tube. REASONS FOR INACCURACY. The scientific reason for inaccuracy in thermom- eters is unevenness of calibre in the tubes, caused by some imperfection in drawing the latter. It will be readily understood that if the bore is wider at one point than at another, the mercury will, with an equal increment of heat or cold, rise or fall a shorter dis- tance at the wider than at the narrower portion, thus giving an apparent rise or fall of temperature less than the true one. This difficulty may be avoided by a process known as calibration, which is as simple as it is correct in its results. Enough mercury is placed in the column to fill a certain portion of it, say two inches; and this space is carefully divided into a large number of de- grees. The mercury is then passed along the tube until the lower end is exactly at the point previously occupied by the upper end; it is very carefully meas- ured, and if its length differs to any appreciable extent from that shown in the former position, the tube is rejected as irregular in bore. This test is made through every portion of the tube ; and to be absolutely reliable, it should be made in both directions, as the surface of the mercury is slightly convex in passing upward and slightly con- cave in passing downward. SCALES. The scales finished in silver have black graduations As spirit boils at 173 degrees F., mercury is always used for high temperatures. It boils at 675 F. in atmosphere, but, under pressure, will register much higher (according to pressure used). 86 WEATHER and figures for contrast, while scales that are oxidized, have white figures and graduations. The same general process is used in manufactur- ing all thermometers, but of course the best glass and the most careful workmen are employed in making the standard grades and more time is spent in testing, graduating and re-testing to insure greater accuracy. SEASONING. After being sealed, but before being tested, the " standard " tubes are " seasoned " by being placed in a vault for from twelve to twenty-four months. This is necessary, as many thermometers are rendered more or less faulty by molecular changes in the bulbs after the instruments have been finally tested. After glass has been heated to the temperature it is in blowing the bulbs, it resumes its minimum bulk gradually, the length of time (that must elapse before shrinkage entirely ceases) varying according to the relative proportions of lead, soda and silica used in the manufacture of the glass. For this reason the bulbs for fine instruments, after being filled and sealed, should be kept from one to two years before being scaled. Enameled glass shrinks more than plain; hence many of the finest instruments have plain glass bulbs sealed to enameled tubes. If manufacturers slight the seasoning process, it saves tieing up a large amount of money, reducing the cost of production correspondingly, but naturally pro- duces an instrument that will prove inferior after a certain time. Various fluids have been and are still used for making ther- mometers, the chief of which are ether, sulphuric acid, alcohol and mercury, the last two being now most extensively favored. SEASONING 87 VARIATION IN THERMOMETER BORE. Seldom, if ever, will two canes have the same size bore. As it is impossible to make tools or gauges to determine the comparative size of the bulb (to the bore) the workman must depend entirely upon his judgment and years of practice. SPIRIT THERMOMETERS. The method of making an alcohol or spirit ther- mometer differs in one important particular from that just described for the mercurial instrument. In the latter case the air and moisture are exhausted (as near- ly as possible) from the tube and bulb before the tube is closed; but when alcohol is used it is necessary to have the tube full of air above the fluid before the sealing takes place. The reason for this is obvious when it is remembered that alcohol is naturally vola- tile and would be wholly unreliable in its movements if placed in a vacuum. After the bulb and part of the tube has been filled with spirits by the same method as that pursued with mercury (heat, of course, being used with great caution), the fluid is drawn down as far as possible by the application of artificial cold, and the top is sealed while the tube is full of air. TEST POINTS. All thermometer scales are determined by the standard hydrogen thermometer. The first step in scale making is to place upon the tube the " test points." The tube is placed vertically in melting ice to ob- tain the freezing point (32° F.). At the end of about half an hour, the tube is raised until the top of the mercury is seen, at which point the tube is marked. As mercury freezes at — 38.02 F., spirit thermometers are used to register low temperatures. 88 WEATHER This process is repeated at 92° when the tube is ready for mounting on the finished scale. The tube is then placed in a bath in which the \vater is kept at a constant temperature (according to an absolute standard) of 62° F., at which point the tube is marked. ABSOLUTE TEST. To have an absolutely accurate test, the water in all baths must be kept in perfect circulation (we use an electrically driven agitator), so that the temper- ature in every part will be the same. TESTS ON OTHER THERMOMETERS. These tests are for the most ordinary kind of ther- mometers, the test points varying according to the character or grade of the instrument. Incubator ther- mometers are tested 90-100-110, clinicals at 95-100- 105-110, while thermometers for other purposes have other test points. ' DEFECTS IN THERMOMETERS. The greater number of defects in ordinary com- mercial thermometers result from improper or care- less construction, the chief errors being usually made in testing, or " pointing " and scaling. Quick and de- cisive tests of thermometers can only be made by com- parison with a standard instrument under water; for currents of air, radiation, reflection, and varying de- grees of sensitiveness due to different sizes and thick- nesses of bulbs, render it impossible to make prompt and definite comparisons in the open air. In some factories, where very cheap instruments are made, the work of pointing is so carelessly done that the water in which the tests are made is often allowed to fall Spirit thermometers are as accurate as mercury, but are slower to register. TESTS— DEFECTS 89 from five to ten degrees below the proper temperature before the workman restores it by adding hot water. If all thermometer tubes could be made with the same size bore — If all could be made with the same capacity bulb — If all could be made without taking into account the personal equation of the workmen — Then, and then only, could the operation of ther- mometer manufacture be made mechanical. PRICE vs. QUALITY. There are thermometers and thermometers. The price is not to be determined by the cost of the small piece of glass and the small amount of mercury enter- ing into its construction any more than the value of a fine microscopic lens is to be determined by the cost of the sand (and other materials which are fused to make the glass) from which the lens is ground. It is claimed, and apparently with good reason, that metallic thermometers (while correct in theory and very ingenious) are impractical. Their action depends upon the difference in expansibility of two strips of different metals (as steel and brass), the flat sides of which are soldered together. After a while these metals become " set," when the registration is anything but accurate. If the manufacturers would (or could afford to) use Invar Steel and fine quality brass and then have all the work done by hand (as in the case of thermographs), permanent accuracy would result, but the cost would be prohibitive. Absolute zero is — 459.4 F. Above this temperature everything scientifically contains heat. 90 WEATHER AN EXPERIMENT BOILING. At a barometric pressure of 29.92 pure water boils at 212° F. Water freed from air (by ebullition) may be raised to over 230° F. without boiling, and if cov- ered with a layer of oil, may be raised to 248° F. without boiling, but above this temperature it sud- denly begins to boil, and with almost explosive violence. AN EXPERIMENT FREEZING. The freezing point of pure water can be dimin- ished by several degrees if the water is previously freed from air by boiling and is then kept in a per- fectly still place. It may be cooled to 5° F. without freezing. When slightly agitated the liquid (or a part of it) at once solidifies. Sea water freezes at about 26°, the ice being quite pure. Note — Manufacturing thermometers for high temperatures (750 degrees to 1,000 degrees F.) requires more than ordinary skill and care. They cannot be sufficiently "seasoned" by storing but must be heated for at least 75 hours to a temperature 100 degrees F. beyond the maximum point at which the finished thermometer can ever be used. It is possible to maintain this high temperature night and day for 75 hours (with approximately no fluctuation) only thru the aid of very finely built and controlled ovens and, on this line, v/e feel we are far in advance of the rest of the world. Thermometers In Meteorological Work RE quite as necessary as barometers and are considered just as important. Care must be exercised in selecting proper exposure, the thermometer being hung where the air can circulate very freely around it. It is well to provide shelter from the direct rays and also from radiated heat of the sun. Errors (some- times due to improper exposure) result in very misleading forecasts being taken. DAILY MAXIMUM AND MINIMUM. The maximum temperature of the 24 hours is reached about 3 or 4 p. m., after the sun has attained its greatest altitude, when the amount of radiated heat from the earth just equals the amount received from the sun. The minimum tem- perature occurs at or just a few minutes before sunrise. The temperature irregularly but grad- ually decreases or in- creases in all direc- ^'^'^' '=^"" tions from a central Areas- of •■l.ou).a-na.-T)i:sl).TeTi7-per4taT«. more or less limited Our earth in its revolution around the sun intercepts less than one-half of one-billionth of the heat sent off by the sun. 92 WEATHER area of high or low temperature. (See drawing on preceding page.) During the day, the ground receives from the sun more heat than it radiates into space. The reverse is the case during the night. It is necessary in meteoro- logical observations, to know the highest temperature of the day and the lowest temperature of the night. Ordinary ther- mometers could only give these indications by a continuous ob- servation, which would be im- practical. The Thermograph (see p. 66) is of course the ideal instru- ment, as it gives all fluctuations and the time of their occurrence, but a maximum and minimum thermometer will give the ex- tremes. The mercury pushes ahead of it an index (see cut). When the mercury recedes, the index remains at the highest point. In the left hand tube this is the lowest, while in the right hand tube it is the highest degree of heat reached. HOW WATER FREEZES. Water contracts when its tem- perature sinks to about 25° F., ?_t> The Eastern Hemisphere is 2° F. warmer than the Western, due to the greater amount of land 80° E. long, and 100° E. long, from Greenwich. M ^-—T--r^--=^ -= k 1 '' i|S| ™| 1 li ill if i \ ||' 11 ^^^^-f-^^l HOW WATER FREEZES 93 but from this point (although the cooling con- tinues) it expands to the freezing point so that J^° represents the point of greatest contraction. In winter, the water at the surface of a lake be- comes cooled and sinks to the bottom and a continual series of currents go on until the whole has a tem- perature of about ^° F.2 g square feet X 100/1=100/8, or 12^ cubic feet per minute. This reading having been taken at 100 feet per minute, to find the velocity of air in the passage we proceed as follows: 100 divided by 88 equals 1.136 miles per hour, as being l/60th of a mile. FORCE OF AIR. To ascertain the force of the air current, multiply the square of velocity of the air in feet per second by .0023. Compasses EOGRAPHICAL meridian of a place is the imaginary plane passing through this place and through the two terres- trial poles, and the meridian is the out- line of this plane upon the surface of the globe. The magnetic meridian is the verti- cal plane passing at this place through the two poles of a compass needle. The magnetic meridian does not co- incide with the geographical meridian and the angle which exists between these two meridians is called declination, or variation of the magnetic needle. In certain parts of the earth the two meridians co- incide. This " line of no variation " is called the " Agonic line." Such a line cuts the east of South America near Cape Hatteras, and traverses Hudson's Bay. Thence it passes through the arctic regions, en- tering the Old World east of the White Sea, traverses the Caspian, cuts the east of Arabia, turns then towards Australia, and passes across the Atlantic circle to complete the circuit. There are places where the declination of the com- pass changes most rapidly. The most remarkable of these is the Coast of Newfoundland, the Gulf of St. Natural iron magnets are exceedingly rare, but a large quantity of magnetic iron is found in Sweden and the states of New York and New Jersey. TRUE NORTH AND SOUTH 143 Lawrence, the seaboard of North America and the English Channel and its approaches. The magnetism of the earth is subject (within cer- tain limitations) to almost continual changes, both in direction and intensity. The magnetic needle is hardly ever absolutely stationary, but exhibits almost contin- ually very minute variations. TRUE NORTH AND SOUTH. The earth being a magnet, a free needle at any place should assume a definite direction, but it does not follow that this direction must be true north and south, as the magnetic poles of the earth do not natur- ally coincide with the geographical poles. Ha compass be at a place in the same meridian with the two poles, the needle will point to true north. But if the magnetic pole lie either west or east of the meridian of the given place, the north end of the needle will deviate either east or west of the true north, and the declination (or variation of the needle) will thus be shown in degrees. CHANGE IN COMPASS VARIATION. In the region between San Francisco and Honolulu recent charts gave systematically too small a value of easterly variation (magnetic declination), so that the compass actually pointed 1° to 2° farther east than shown by the charts used in directing the course of a vessel tfetween these ports. Since the distance is about 2,000 miles, and assuming an average systematic error of but 1°, it might transpire during a cloudy or foggy passage, when no sun or stars would be visible and sole dependence would have to be put upon the com- The end of the needle pointing south contains northern magnetism because (according to the law of magnetism) like poles repel, while unlike poles attract. 144 WEATHER pass and the log, that the vessel at the end of her 2,000- mile voyage would find herself too far north by about l/60th of the distance traveled (roughly, 35 miles). CHANGES IN DECLINATION OF COMPASS. Illustrations of the difference in magnetic varia- tions are well shown by the following: In London, in 1576, the declination was 11°, 15' east of true north. Eighty years later, it pointed due north, and in 1760, there is a record of it pointing 19°, 13' west of north. The westerly declination attained its maximum about 1819, when its reading was 24°, 40'. Since then the needle has been traveling slightly eastward, the pres- ent annual rate of decrease being more than 8'. In 1904, it was 16°, 15'. THE DIP OF THE COMPASS. If we imagine the earth as a huge round magnet (with the north and south poles opposite one another) and hold a magnetic needle which is accurately bal- anced (at the equator of that sphere) it will not only point north and south but assume a perfectly horizon- tal position. If it is moved nearer to the north end of the sphere, that end of the needle will dip, and the same thing takes places if it is held towards the south. At either pole it would point to the earth (at an angle of 90° F.). This is called the inclination or dip of the compass. Robert Normas is credited with the discovery of the dip of the compass as far back as 1576. WHERE MAGNETISM IS GREATEST. By counting the vibrations of a delicate dipping Between 5 and 7:30 a. m. the positive electricity is at its minimum. It reaches its first maximum about 9:30 a. m., when it again de- creases—from 2:30 to 4:30. It increases, reaching its second maxi- mum from 6:30 to 9:30, EARLY COMPASSES 145 needle, it will be found that the strength of the earth's magnetism increases as we go from the equator, towards either of the poles. COMPASSES. A compass is probably best described as a mag- netized needle pivoted upon its center to swing freely on a hardened point; used to indicate the magnetic meridian and, by the means of a graduated dial or circle, the azimuths of bearing of objects from this meridian. EARLY COMPASSES. It is difficult to determine who first put magnetism to practical use, but the early Chinese appear to have been acquainted with the polarity prop- erty of loadstone (mag- netic iron ore) and used it as a compass by float- ing it in water upon a piece of cork. INVENTED. F 1 a V io Goija, of Amalfi (early part of the fourteenth century) is said to have been the first to have invented the magnetic needle. Dr. Gilbert (1600) was brought to Italy from There is evidence Fig. 1. compass states that the China by Marco Polo about 1295. of its having been used in France about the year 1150, I^ightning often inverts the poles of compass needles. 146 WEATHER in Syria about the same period and in Norway previ- ous to 1266. There are many kinds of compasses, each adapted for a certain purpose when used by surveyors, hunts- men, mariners and for the military, .et al. PRISMATIC COMPASS. The prismatic compass (Figs. 1 and 2) is used for surveying, more espe- cially for military pur- poses. It consists of a brass box from 2" to 4" in diameter. Upon the pivot is balanced the magnetic needle, to the top of which is fixed a card correctly divided into degrees. In the best quality compasses, a divided aluminum ring is sub- stituted in place of the card dial, as it makes a far more satisfactory in- strument and less liable to derangement. Fig. 2. OBSERVATION OF ANGLES. As horizontal angles can be observed with great rapidity, it is a very valuable instrument to the mili- tary surveyor, who can make observations (holding the compass in his hands) with all the accuracy neces- sary for an observation or sketch; to obtain absolute accuracy the use of a tripod stand is necessary. The The greatest amount of electricity is observed when barometric pressure is highest. MILITARY PRISMATIC COMPASS 147 compass illustrated (Fig. 3) is particularly adapted for this purpose. Fig. 3. MILITARY PRISMATIC COMPASS. The sight vane and prism box must be turned up so that the instrument appears as illustrated in Figs. 1 and 2, then set or hold the instrument as nearly hori- zontal as possible so that the dial may revolve freely. The blue of the sky is attributable to the reflection of sunshine from minute particles of oxygen and nitrogen in the air. 148 WEATHER The divisions on the dial can be finely focused by either raising or lowering the prism box in its socket. Look at the object being sighted (through the slit in the prism box) until the fine hair in the sight vane cuts through the object. Then, by looking through the prism box at the dial, a certain number can be read. That degree number is the magnetic bearing of the object from the point of observation. Should the ob- server wish to take an angle from that object to an- other, repeat the operation by sighting the second object (being careful to revolve the compass box on its center), and after that reading has been noted, the value of the angle is the difference between the two readings taken. If the first reading were 249°, 30', and the second reading 319°, 30', the value of the angle would be 70°. AZIMUTH SHADES AND MIRROR ATTACHMENTS. For the purpose of taking the bearing of objects considerably above or below the level of the observer, mirrors and sun glasses (" azimuth shades and mirror attachments ") are applied to a certain type of pris- matic compasses. (Fig. 4.) The mirror slides up and down the sight vane with sufficient friction to remain at any desired part of the vane. It can be put on with its face either above or below the horizontal plane of the eye. If the instru- ment is used for obtaining the magnetic azimuth of the sun, the dark glasses must be placed between the sun's image and the eye. STOP. On all good quality prismatic compasses, there is a stop on the side of the compass box, which (by fric- Heated air is a better conductor than cold. AZIMUTH PRISMATIC COMPASS 149 Fig. 4. Azimuth Prismatic Compass, 150 WEATHER tion) stops the card from moving when desired. By an ingenious arrangement the card or aluminum ring is lifted off its center when the sight is closed down, preventing the constant playing of the needle, which would wear the fine agate and point upon which it is balanced. The ship compass, which Sir Wm. Thompson (Lord Kelvin) invented, has been taken as the stand- ard for the marine world. THE mariners' COMPASS. The mariners' compass consists of a copper or brass bowl, hemispherical in shape, into which is mounted a compass card fitted upon a delicate point, the dial re- volving upon an agate cap to insure its working easily. As the roll and pitch of a vessel would be liable to unsettle the ordinary compasses, these bowls are usu- ally filled with some alcoholic liquid to keep the card steady. CONSTRUCTION. The bowls' of the compasses are supported in a ring by two pivots projecting from the opposite sides of the box. This ring is swung by two pivots at right angles to the first. This arrangement (called "gim- balling ") keeps the pivot of the compass always verti- cal, the bowl being weighted at the bottom, so that its center of gravity is considerably below the points of suspension. The dial card (with its attachments) is constructed as light as possible to make the compass very sensitive. It consists of a thin aluminum circular rim, at- tached by silk strings to a small aluminum disc, in the center of which is an agate cap. To the strings is gummed a thin paper annulus, on which is marked the The Peruvians, in order to preserve the shoots of young plants from freezing, light great fires, the smoke of which, producing an arti- ficial cloud, hinders the cooling produced by radiation. AN EXPERIMENT 151 points of the compass. The pivot upon which this dial rests is made of platinum-iridium, to insure hardness and freedom from oxidization. There are eight magnets (about as thick as knitting needles, and from two to three inches long), placed symmetrically on each side of the center. These lie in a plane about lys inches below the card, being sup- ported from the aluminum ring by silk strings. Since the weight of the card (magnets and all) is not more than 11 J4 grams, and since the needles are some way below the point of suspension, the card remains hori- zontal even when there is considerable tendency of the needles to dip. The bowl of Lord Kelvin's compass has a com- partment at its base, partially filled with castor oil to prevent oscillations. A MAGNETIC EXPERIMENT. To induce a small amount of natural magnetism into a bar of soft iron (such as an ordinary poker), tie a silk string around the center, holding it so that it points due north and south at the proper angle of dip. By lightly tapping the iron with a piece of metal, the molecules will arrange themselves by the induction of natural magnetism which is constantly passing around us. It will not retain its power for any length of time and will lose it instantly if dropped or put into a fire. SHIPS ARE MAGNETS. In this manner, ships become huge magnets, as the hammering of plates, rivets, etc., in the construction induces natural magnetism. A great amount of it is generally lost on the first voyage, due to the buffeting of the waves and the vibration of the machinery and In some parts of the world nearly all the moisture which the earth ever receives comes in the form of dew. This is particularly true of some parts of Egypt and Arabia. 152 WEATHER engines. The magnetism which is left is called perma- nent magnetism, as it undergoes very little subsequent loss of power. Magnetizing a Bar of Iron. WHY SHIPS ARE SWUNG. Before leaving port, ships are " swung " for the adjustment of the compass to compensate for the local attraction of iron and steel in the ship. A sufficient number of hard steel magnets are then placed in the binnacle (under the compass) in such a manner as to exactly counterbalance the permanent magnetism of the ship. Other influences are corrected by a bar of soft iron (Flinders Bar) placed immediately forward or abaft the binnacle. It must be of the proper length to produce exact compensation when its upper end is on a level with the needles of the compass. HOW SHIPS ARE SWUNG. The process consists in observing the direction of the Standard Compass on board the vessel, as the A fall of one foot of snow may be roughly taken as equal to an inch of rain. METHODS OF COMPENSATION 153 ship's head points N., NE., E., SE., etc., and compar- ing it with that of an undisturbed compass on shore. In this way the error of the compass on each point is ascertained, and from it the table of errors is drawn off. By examining this table, the navigating officer as- certains how much of the errors are due to the perma- nent magnetism in the ship, and how much to tempor- ary induction in the vertical and horizontal iron. METHODS OF COMPENSATION. These several errors are compensated for, first, by permanent magnets in the binnacle ; second, by the Flinders bar; third, by the port or starboard iron sj-heres. Fig. 5. Hunter Watch Case Compass. Many types of compasses are used by travelers, tourists and sportsmen, the most popular styles being mounted in hunter watch cases (Fig. 5) or contained in brass boxes with lifting covers. Most of these have Heavy dews in hot weather indicate a continuance of fair weather. 154 WEATHER the dial (fixed in the base of the compass) graduated 0° to 90° between N. and E., E. and S., S. and W., and W. and N. The " bar needle," which is usu- ally employed in these compasses, has a jeweled center, the whole revolving upon a delicate steel point. PROTECTION OF JEWELS. An automatic stop is fitted to the better styles, the Ltiminous Dial Compass spring of the lid, when closed, coming in contact with a lifter, which " throws " the needle and jewel cap off the point, preventing friction and wear. Fig. 6 illustrates a luminous dial compass, which has great advantage over the ordinary kind, as by ex- In August, 1851, hailstones weighing 18 ounces — diameter 4 inches, circumference 12^ inches, fell in New Hampshire. Hailstones weigh- ing IS ounces fell in Pittsburg. HOW TO SET COMPASSES 155 posure to daylight, the dial becomes luminous (can be seen throughout the night). In the lid is inserted a small glass having a vertical line etched upon it. By means of the small sight hole in the ring or bow of the compass and the line on the glass, it is quite a simple matter to readily ascertain the magnetic direc- tion of any place. MILITARY MARCHING. In military marching, all magnetic directions are given from 0° to 360°, counting from right to left. It is necessary that all military compasses, having fixed dials of degrees, should be figured from right to left and all compasses having movable or floating dials of degrees should be figured from left to right. This will be apparent by the following examples : TO SET A FIXED DIAL COMPASS. To set a compass (having fixed dial) to a given magnetic bearing, say 45°, the compass should be turned until the magnetic needle stands directly over the point at 45°, and the march made in the direction of the north point on the dial. TO SET A FLOATING DIAL COMPASS. To set a compass (having a floating dial of de- grees) to the same magnetic bearing, the compass should be turned until the central or luminous line in the lid of the compass is directly over the point at 45°, and the march made in the direction of the central line in lid of the case. Sun-Dials Let others tell of storms and showers, I'll only count your sun»y hours." HE history of the sun-dial is the history of the world's gardens. According to the Old Testament, Ahaz erected a dial (Damascus, 771 B. C.) which is men- tioned in the account of the miraculous cure of his son, Hezekiah. Greek and Roman specimens are fairly common, but to the Chaldeans, as far as we know, belongs the honor of first constructing sun-dials. They at- tained their greatest vogue late in the Middle Ages, being used in the most elaborate forms for decorative effect. On churches, they range from the primitive dial of the Saxons to the more or less elaborate ones of to-day. In tropical countries its first form was a staff planted upright in the ground. The time was reck- oned by the length of the shadow, as the equatorial day does not vary in length the year around. At a distance from the equator, the direction of the shadow of some promment mountain, tree or object was noted. " Time is Too slow for those who wait. Too swift for those who fear, Too long for those who grieve. Too short for those who rejoice. But for those who love. Time is eternity." Dr. Henry Van Dyke. THE HORIZONTAL DIAL 157 The most effective form, from the decorative point of view, is the horizontal dial, often elaborately en- graved, the graceful gnomen rising from the top of an ornamental pedestal. Outside Vertical Sun Dial. With this may also be classed the universal equa- torial dial. Placed on the lawn, in the center of a path, on a terrace or against a background of shrubs, its effect cannot be over-estimated. Whether in a small town, a suburban garden, or in the grounds of a country mansion, it always has a quiet, restful, old- time character of its own. In civilized lands, the influence of the sun-dial A red sim has water in its eye. 158 WEATHER as a timekeeper is almost past, and therefore, while it can be made to any degree of accuracy and fine reading, yet (when used in its present proper sphere as an ornament), minute detail is only confusing, and the necessary solid masonry setting a superfluous ex- pense. As it is, the shadow (of the gnomen on the dial) caused by the yearly revolution of the earth around the sun, we might repeat a few facts regarding the sun that we have all known so long as to have almost forgotten. " The sun is the center of the solar system, remain- ing constantly fixed in its position. The earth makes a complete revolution around the sun in 365 days, 5 hours, 48 minutes and 46 seconds. It also rotates on its axis (an imaginary line passing through its cen- ter) once in 23 hours, 56 minutes and 4 seconds, mean time, turning from west to east. The sun is the main cause of every weather change. The sun determines whether the earth shall be hot or cold. Absence of sun's rays makes the North Pole a continent of ice ; plenty of sun's rays makes the Equa- tor a furnace. The sun's rays, by heating one land more than another, cause winds, hurricanes and cyclones. The sun is much brighter and hotter at certain periods than at others. According to Professor S. P. Langley, during 1904 there was a notable decrease in the amount of heat received from the sun. RISING AND SETTING. The sun " rises " in the east and " sets " in the west, being due south near round 12 o'clock at noon. The volume of the sua exceeds the earth's nearly 1,253,000 times; the mean distance is 91,430,000 miles. EQUATORIAL SUN DIAL 159 The gnomen is set at an angle (parallel to the earth's axis) upon a vertical dial divided into the hours of the day, and facing south. The shadow of the Equatorial Sun Dxal. gnomen (due to the difference in position of the earth to the sun during her daily revolution) will point to the hour. By applying the correction of the equation Sun bright noon — ^red night. 160 WEATHER table, usually supplied with sun-dials (sometimes en- graved on them), very accurate time can be obtained. EQUATORIAL SUN DIAL. Illustration shows an Equatorial Universal Sun- Dial, so called because it can be easily set to the exact latitude of the place where it is to be fixed. The side of the metal curved limb, holding the metal curved gnomen, is a divided arc of 90°, so that the instrument Design of Porcelain Base Plate. can be readily adjusted to the latitude of any differ- ent locality. The porcelain time arc is divided to read to five minutes. The wire rod gnomen being fixed to its proper latitude, makes it parallel to the earth's polar axis, ready for use. The shadow of the wire rod is The light of the sun is said to be equal to 670,000 times that of an ordinary wax candle at a distance of one foot. LARGEST SUN DIAL 161 in the form of a line only, and is very clearly seen. The base plates of these instruments usually have printed upon them the correction of time applying to dials, also giving mean time at the various parts of the world at noon ; Greenwich mean time. TYPES OF SUN DIALS. Equatorial, horizontal and vertical dials are the ones most commonly used, although there are others made, not now often seen. One of these is known as the '■ Cross " dial, made in the shape of a cross, the hours reading on the sides of the stem and arms. The " Cannon " dial has a lens so arranged that when the noon hour is reached the rays of the sun are so cen- tered through the lens as to fire a cannon. Another type is the " Anelemmic " dial, consisting of a vertical pole, fixed in a lawn, the hours being marked by flower beds surrounding it.- LARGEST SUN DIAL. The largest sun-dial in the world is at Delhi, in India, being 58 feet high. Its construction is unique, as a flight of stone steps (parallel to the axis of the earth) constitutes the gnomen. The shadow falls upon dials (116 feet in diameter) on the marble walls which support the sun-dial. SUNSHINE RECORDERS. The records of sunshine may more properly be called records of the duration of bright sunshine, as, with one or two exceptions, recorders do not measure the brightness or intensity of the sunshine. The instruments which aim to record the intensity consist generally of two thermometers, the bulb of one of which is coated with lamp black. The total heat emitted by the sun would melt 2,600,000,000,000 tons of ice per hour. 162 WEATHER DIFFERENT FORMS The three forms of bright sunshine recorders at present in use are the Campbell-Stokes burning re- corder (cut No. 1), the Jordan (or photographic re- corder) and the electrical thermometric recorder, No. 2. THE CAMPBELL-STOKES RECORDER. The Campbell-Stokes Recorder was originally de- signed in a rough form by Mr. J. P. Campbell, of Ken- sington, England, in 1853; the present form of zodi- acal belt being the introduction of Professor Stokes, of Cambridge, England. This belt is divided into three zones, each zone be- ing constructed to receive a strip of card, which, fol- lowing the curve, may be taken to represent the re- spective zone of spherical surface. In front of this belt is a groUtid and polished crystal sphere, which acts as a lens or burning glass, and scorches a trace, showing the duration of bright sunshine upon these strips of card. On the limb of the Campbell Stokes Recorder will be found a divided arc which will enable the user to set the instrument to the proper latitude to record ac- curately. When properly set, this instrument makes an excellent sun-dial. EXPOSURE. It is hardly necessary to add that the point select- ed for the exposure of sunshine recorders should command an uninterrupted view of the sun at all hours of the day and at all seasons of the year. Some allowance must always be made for loss of record (during early morning and late afternoon hours) owing to the poor light in later seasons. A solar halo indicates bad weatlier. SUNSHINE RECORDERS SUNSHINE RECORDERS. 163 No. 1. The light of the sun is 600,000 times as powerful as that of the moon; and 16,000,000,000 times as powerful as that of Centauri, the third in brightness of all the stars. The sun is 5,550,000,000 times as bright as Jupiter, and 80,000,000,000 times as bright as Neptune. 164 WEATHER JORDAN RECORDER. The Jordan Recorder consists of a closed metal cylinder supported on a frame so that the axis of the cylinder can be set at an inclined position, parallel to the earth's polar axis. The interior of the cylinder is fitted with curved metal pieces to hold sheets of sensitized photographic paper. Two notched slides are fitted to a scale, which represents the days of the month. These slides are placed on the sides of the cylinder, and on each side of these slides is a pin hole, which enables the paper to become exposed, and thus record the amount of sun- shine. When set to the proper latitude, the sun apparently ' passes over the recorder in a circle. The record on a properly adjusted instrument will, of course, consist of straight lines, but a great variety of curved lines or traces will be obtained if the instrument is improperly adjusted. "^ THEEMOMETRIC SUNSHINE RECORDER. The Thermometric Sun- shine Recorder consists of a straight glass tube with cylindrical bulbs, the whole encased in a protecting glass sheath. Mercury is used to separate the air in the two bulbs, a small quantity with a little alcohol (the alcohol plays an important part in the thermometric action of _ _ _ the instrument, and also acts No. 2. 3-5 a lubricant for the mer- When the sun sets bright and clear. An easterly wind you need not fear. THERMOMETRIC RECORDER 165 cury), being inserted in the bottom and stem of the lower bulb — imagining the instrument is held vertically. The lower bulb is smoothly coated with lamp black- The two bulbs are then filled with pure air and sealed. Passing through the outer glass sheaths are two plati- num wires, which are connected through the bore of the inner glass tube, so that electrical connections can be made when the sun is shining, which causes the mercury to rise and thus makes the electrical connec- tion, marking the record on a chart. It is necessary to expose this instrument to the south, with the black- ened end down; the inclination will be approximately 45° from the vertical. INDEX Absolute Humidity Adjustment of Barometers . Aerial Meteors . . . . Agonic Line Airey's Table of Altitude Air, Height of " Pressure of . . ...... " Weight at Sea Level . . . . Alcohol Thermometers, how made .... Altitude Barographs . " Hand, use of Aneroids of Clouds " Scales, method of reading Tables Alto Barographs . . ... Anemometers Birams . . . " Lownes " Robinsons Aneroid Barometers, how compensated . . " " how to adjust to standard reading . ... " construction of . . . " definition of ... " for Surveying . . ...... " how to reduce to sea level . " " set . . " observation of . . . " Recording " Surveying, how to read . . use of "C. & T." Altitude Hand . . " vacuums, illustration of . " Watch and Pocket Styles Aqueoris Meters Area of Earth's Surface . 98 44 12 142 49 3 4 4 '87 64 34 lOS 46 36-50 64 139 136 136 44 44 58 5 51 34 13 12-13 61 51 34 58 46 12 4 168 INDEX Atmosphere . . 3 " weight of . 3 Atmospheric Pressures, how to trace by winds 16 Avalanche Wind 135 Barographs . . . 61 " advantage of 64 " for altitude ... . . 64 " and Thermographs, combined 69 Barometer, discovery of . . 8 " how compensated 44 " how to set 13 living .... 20 " reading, what indicates 26 " Recording . . 61 " reduced to sea level 34 Spider and Frog . 20 " stationary, what indicates . 17-26 uses in railroading 41 " what falling shows . 14-17-26 " what rising shows 14-17-26 " words on dial of 14 Barometers, adjustment of . 44 " Mercurial 94 Barometric inches, value of . 48 Blowing Bulbs on Thermometers -82 Boiling Point Apparatus 57 Boyle's Scale on Thermometers 78 Biram's Anemometers 139 Bulbs on Thermometers 82 Calibration of Thermometers 73 Cause of Cyclones 39 " " Fogs . . 110 " "_ Frost 116 " Rain 117 " " Wind . . 133 Celsius Thermometers 79 Centigrade Thermometers 79 Change of Aneroid 17 Charts, Weather 21 Cloudbursts . . . 118 Clouds 103 " altitude of 105 " color of 106 " formation of .... 103 " nature of 103 INDEX 169 Clouds, Thunder .... 121 " various kinds . ... . . 106 " velocity of ... . . . lOS Cold Waves; formation of . . . 75 Color and Nature of Clouds .... 103 Combined Barograph and Thermograph 69 Compass, declination of 142 Compasses, compensation of Marine . . ISl first use of . . 145 " for Ships at Sea . . . 152 " Inventor of 145 " Luminous 155 Mariners' . . . . 150 " Military 155 " Prismatic . 146 " " examples of . . . 149 " reading 149 Ship . . 150 Compensation of Barographs . . . . 62 " " Barometers 43 " " Marine Compasses . . . . . 150 Construction of Aneroid . . . . 58 " " Barographs . . 61 " C. & T." Hand on Aneroids . . . 34 Cyclones ...... . . 39 " cause of . . ... 39 Cyclonic Storms, cause of . . . 124 Declination of Compass . . 142 Definition of Aneroid . . . 5 " " Isobars . .... 22 " " Isotherms * ... 28 Delance Thermometer 78 Depth of Ocean 93 Determine Velocity of Wind, how to 136 Dew . . ... 108-114 Dew Point ... 114 Diameter of Fog Particles . 109 Different Forms of Lightning . . . 121 " " Thunder . . 124 " Kinds of Rain Gauges 125 Dip of Compass, discoverer of .... 144 Direction of Thunderstorms 18 " Wind . . 132 Discovery of Barometer . . 8 Duration of Lightning Flash ... 120 170 INDEX Dust Storms ... Ill Earliest Records of Weather 6 Earth, area of surface ... .4 " Magnetism, change of . 143 " revolution of . . 158 Effect of Altitude on Barometer 34 " " " " Temperature . 76 " " Low Temperature on Lakes 92 " " Pressure on Temperature 90 " " Sun on Weather . 11 " " Weather on Humans 8 " " Wind on Thermometer . . 17 " " Winds at Different Velocities 140 Errors in Poor Exposure of Rain Gauges . . . 131 " " Reading of Barometers Due to Altitude 34 Evaporation . 102 Example for Taking Relative Humidity 101 " of Aneroid Reading . . 48 Exposure of Rain Gauges . 131 Fahrenheit's Thermometer . 76 Falling Barometer ... ... 14-17 Ferdinand II. Thermometer . . 11 Filling Thermometer Tubes ... . 83 Flinders Bar, use of in Compasses 152 Fogs . . . 109 cause of . 109 " diameter of particles 109 " difference in Clouds . 103 Force of Wind per Square Foot . . 135 Forecasting . 12-16 Formation of Cold Waves . 75 . " Clouds . . .103 " " Snow . . 114 Frog as Barometer . 20 Frost . 114 Geographical Meridian . . . . 142 Graduating Scales on Thermometers . . 84 Gulf Stream, fogs on . . .110 " " temperature of 110 Hail . . . 110 Heat ...... 75 Heaviest Rain in Storm .... . 124 Height at Which Humans Can Live . . 5 Height of Air . 3 Highs and Lows on Weather Map, use of . . . 29 INDEX 171 History of Sun Dial . . 156 Hooke's Scale on Thermometer . 78 How to Read Altitude Scales . . . 46-53 Humidity .... 95 Hygrodeik . ... 100 Hygrometers . 9S Hypsometers . . . 56 Illustration of Weather Map . 31 Inventor of Compass .... . 145 Isobars, definition of . . 21-28-39 Isotherms " " . 28 Jordan Sunshine Recorder . . 164 Kelvin's Compass . . . ! . 151 Kircher's Thermometer ... .78 Lakes, effect of cold in ... . 93 Largest Sundial . . . . . 162 Lightning 120 different forms of . . 121 " duration of flash . . 120 Living Barometers .... . . 20 Lownes' Anemometer 136 " Lows " and " Highs " on Weather Map, use of 29 Luminous Compasses . ... 155 Luminous Meteors ... ... .... 12 Magnetic Meridian . 142 Magnetism . . . 143 " natural ... . . 151 " permanent .... 152 Manufacture of Thermometers ... 80 Map, Use of "Highs" and "Lows" on Weather 29 Marine Compasses .... . . 150 " " construction of ISO Maximum Temperature ... 91 " Thermometers 92 Mercurial Barometers ..... 94 Meridian, geographical . . 142 " magnetic . 142 Meteors, aerial, aqueous, luminous . . 12 Method of Surveying Ships for Adjustment of Compasses .... 150 Military Compasses . . . . . . 155 Minimum Temperature .... . . 91 Thermometer . . . 92 Moisture . ■ ■ • 95 Monsoon, definition of ... 118-135 172 INDEX Movement of Barometer, how constructed 58 Natural Magnetism ... . . 151 Observation of Aneroid 12 Ocean, Depth of . . . 93 Permanent Magnetism 152 Pluviometers 125 Pocket Aneroids .... 46 Pointing Thermometer Tube 87 Precipitation, when it occurs . 104 Predictions, Weather, how made 11 Pressure of Air 4 " Wind 133 Prismatic Compasses . 146 Process of Calibrating Thermometers. 85 " " Filling Tube of Thermometer 83 " " Graduating Thermometers 84 " Making Thermometers . 80 " Seasoning Thermometers 86 " Testing Thermometers 87 Psychrometers, Sling 101 Railroading, Barometer in 41 Rainbow 116 Rainfall . . 117 Rain Drawn From Hills 118 " Gauges, different kinds of 125 " exposure of 130 " Heaviest During Fall 124 " Red . . 111 " Winds . 119 Reading of Aneroid 12 Reamur Thermometers 79 Recording Barometers 61 " Thermometers 66-86 " " and Barometers Combined 69 Recorder, Sunshine . 161 Records, Earliest of Weather 6 Reduce Aneroids to Sea Level . . 34 Red Rain .... 111 Relative Humidity 98 Revolution of Earth . . ... 158 Robinson's Anemometers 136 Rules for Converting One Thermometer Scale to Another 136 Scales, Altitude, how to read 46-64 " Fahrenheit's Thermometer 76 INDEX 173 Scales, Graduating on Thermometers . 84 Sea Level, how to reduce Barometers to. . 34 " " weight of air at ... 4 Seasoning Thermometer Tubes . 86 Set Aneroids, how to .... . 44 Ship's Compass . . " construction of " how swung Signs, Weather Simoon ... . 152 ISO 152 6-16 135 Sky . . . . . . 106 Sleet .... . . . Ill Sling Hygrometer .... . 101 Snow . . . ... 114 " Gauges . . . 132 " to measure fall of 132 Solar Heat ..... . 76 Sound, rate of travel . . . 122 Spider as Barometer .... 20 Spirit Thermometers, how made . 87 Squalls . . . 135 Stationary Barometer . . 17 Storms, causes of .... 39 Dust . Ill " when occur 11 Sun . . .... . 10-75-158 " effect of on weather . . 11 " rising and setting of . 158 Sundials ... .... . 156 " largest .... . . 117 Sunshine Recorder (Campbell-Stokes) 162 (Jordan) . 164 " " Thermometric 164 Surveying Aneroids ..... 51 Sympiesometer .... ... 45 Table Giving Value of Altitudes in Inches 36 " of Altitudes, Prof. Airey . 50 Temperature .... .... . 75 " Maximum, when reached 91 " Minimum " " . 91 of Gulf Stream . . HO Terms Used in Weather . . 32 Terrestrial Heat . . 75 Testing Thermometers . .... 87 Thermographs ... . ... ... 66 174 INDEX Thermometer, effect of wind on 17 Thermometers . . • ;• • 75 " and Barometers, Recording, combined 69 Boyle . . 78 Bulbs 81 " Calibration of . . 73-85 " Celsius ... 79 " Centigrade 78 " Delance . 78 Drebbels ... !(> Essay on (1738-39) 70 Exposure of 91 Fahrenheit's 7o " Ferdinand II. 76 " filling tubes 84 " first manufacture of 76 " Fowler . . . . 79 Glass Tubes, manufacture of 80 " Graduating Scales 84 Hooke's .... 78 " in Meteorological Work 90 " Kircher's 78 " Maximum, Minimum 91 Mercennes 78 Reamur 78 Recording 66 " Sanctorious 79 " Seasoning Tubes 86 Spirit and Alcohol 87 Testing Tubes 87 Thermometric Sunshine Recorder 164 Thunder 122 cause of noise 122 " Clouds . . 121 different kinds 124 most frequent time for storms 123 Thunderstorms, direction of 18 Tornadoes, cause of . . . . 124 Torricelli (discoveret of Barometer) 8-77-94 Use of Flinders Bar . . . 152 Value (in feet) of Barometric Inches 48 Variation of Compass . . . 144 Velocity of Clouds . . 105 " " Air, how to determine 141 Verniers, how to read . . . 52 INDEX 175 Vacuum Barometer, how constructed 58 Volcanic Winds .... ... . 135 Watch Aneroids ..... 46 Weather Bureau . . 10-23 Charts . 21 " Earliest Records of . . 6 " Effect of on Humans . . 7 " " Sun on 11 " " Wind on . . 13-26 " Indications ... . . 26 Map 28 " " illustration of . . . 31 " Use of "Highs" and "Lows" on 29 " Predictions, how made 11 " Proverbs .... 6 " Signs . 6-16 Terms . 32 Weight of Atmosphere .... 4 at Sea Level 4 Wet and Dry Bulb Thermometer 95 Wind .... 18 " cause of . . . . _ 133 " directions of 133 " effect on Thermometer 17 " Weather . . 13-26 " force per square foot . 135-140 " Gauge, different forms of 136 " how to trace Atmospheric pressures by 16 " kinds of . . . . 135-140 " Rain .... . 119 Words on Barometers 14