Meteorology. the science made great and rapid advances by the investigations undertaken by distinguished philosophers into the laws which regulate the changes of the atmospheric phenomena. The theory of the trade-winds was first propounded by George Hadley in the Philosophical Transactions for 1735; and it may be mentioned as a remarkable fact that for about half a century it remained quite unnoticed, when it was independently arrived at by Dalton, and published in his essays. The publication of Dalton's Meteorological Essays, in 1793, marks an epoch in meteorology. It is the first instance of the principles of philosophy being brought to bear on the explanation of the intricate phenomena of the atmosphere. The idea that vapor is an independent elastic fluid, and that all elastic fluids, whether alone or mixed, exist independently; the great principles of motion of the atmosphere; the theory of winds, their effect on the barometer, and their relation to the temperature and rain; observations on the height of clouds, on thunder, and on meteors; and the relations of magnetism and the aurora borealis, are some of the important questions discussed in these remarkable essays, with an acuteness, a fullness, and a breadth of view that leave little to be desired. One of the most interesting and truthful subjects of inquiry that engaged the attention of meteorologists was dew. The observations on this subject were first collected and reduced to a perfect theory by Dr. Wells. See DEW. In 1823 Daniell published his Meteorological Essays and Observations, which, while adding largely to our knowledge in almost every department of the subject, are chiefly valuable as bearing on the hygrometry of the atmosphere. Though the practical advantages which he anticipated would flow from it have not been realized, yet this difficult and still obscure department of meteorology stands indebted to him more than to any other philosopher. The law of the diffusion of vapor through the air, its influence on the barometric pressure, and its relations to the other constituents of the atmosphere are among the least satisfactorily determined questions in meteorology. Since this element is so important as an indicator of storms and other changes of the weather, and since so much remains still to be achieved, it is to be hoped that it will soon be more thoroughly investigated. A most important addition has lately been made to our knowledge of the vapor of the atmosphere by professor Tyndall, in his experiments on radiant heat, especially as regards the gases. The vapor of water is there shown to exert extraordinary energy as a radiant and absorbent of heat; and hence the vapor dissolved in the air acts the part of a covering or protection to the earth. As it is, to some extent, impervious to solar and terrestrial radiation, it follows that if the air were quite drained of its moisture, the extremes of heat and cold would be so intense and insufferable that all life would instantly perish, there being no screen shielding the earth from the scorching glare of the sun by day and from the equally scorching and blighting effects of its own radiation by night. It is to be expected that this great discovery will soon throw light on many questions of meteorology. Electrical observations have been, of all meteorological observations, perhaps the least productive, partly owing to their scantiness, from the expense and trouble attending them, and partly, no doubt, to the free and bad use made of the name of electricity by crude theorists in explaining phenomena of which it would have been wiser to have confessed their ignorance. But the brilliant discoveries which have recently been made on the mutual relations of heat, motion, electricity, magnetism, and the other forces of matter, lead us to indulge the hope that the application of these results to meteorology will be attended with discoveries equally brilliant and important. Humboldt's treatise on Isothermal Lines (1817) constitutes a notable epoch in experimental meteorology. Dové has since continued the investigation, and in his splendid work, On the Distribution of Heat on the Surface of the Globe, has given charts of the world, showing the temperature for each month and for the year, and also charts of abnormal temperatures. It is scarcely possible to overestimate the value of this work, for though, to a considerable extent, the lines are hypothetical, there can be no doubt that a close approximation to the march of mean temperature and its distribution over the earth through the year has been arrived at. The idea has been carried out with greater fullness of detail by the United States government in the beautiful and elaborate series of charts of temperature and rainfall given in the Army Meteorological Register for 1855. In these charts the temperature and rainfall in the different seasons for every part of the United States, deduced from accurate observations, may be seen at a glance. Buchan has published isothermals for the British isles, Mohn for Norway, and Blandford for Hindustan; and isothermals for the sea have been published by the admiralty. The establishment of meteorological societies during the last twenty years must also be commemorated as contributing in a high degree to the solid advancement of the science which, more than any other, must depend on extensive and carefully conducted observation. In this respect, the United States stand pre-eminent, the observers there numbering nearly 800. Great Britain is also well represented in the English and Scottish societies, which together number above 200 observers. In France, Germany, Russia, etc., the science is also being widely cultivated. Owing to the disastrous flooding of the Rhone, an inquiry has been carried on for several years, having for its object the determination of those causes which affect the rainfall in the basins of the Rhone and Saône. Observers in Germany and Great Britain have been secured to co-operate with Meteorology. the French observers, and under the management of a commission it may be expected that important conclusions respecting the rainfall and the progress of storms will be arrived at, and means devised to avert the calamity of these great Hoods by timely warning being given of their approach. A special object of meteorological societies is to ascertain the degrees of heat, cold, and moisture in various localities, and the usual periods of their occurrence, together with their effects on the health of the people and upon the different agricultural productions; and by searching into the laws by which the growth of such products is regulated the agriculturists may be enabled to judge with some degree of certainty whether any given article can be profitably cultivated. But perhaps none of the arts have benefited to so large an extent by the labors of meteorologists, as navigation. The knowledge thus acquired of the prevailing winds over the different parts of the earth during the different seasons of the year-and the regions of storms and calms-and the laws of storms, have both saved innumerable lives, and by pointing out the most expeditious routes to be followed, shortened voyages to a remarkable degree. In connection with this, the name of Captain Maury (q. v.) deserves special commendation for the signal service he has rendered to navigation. Another fruit of the multiplication of meteorological stations is the prediction of storms and "forecasts" of the weather, which have been carried on in the United States, and commenced with ability and success by Admiral Fitzroy in England. These "forecasts" are based on telegrams which are received every morning from above forty selected stations in Great Britain and Ireland, and on the continent, from Haparanda as far south as Lisbon. These telegrams give the exact state of the barometer, thermometer, hygrometer, and rain-gauge, with the direction and force of the wind, and appearance of the sky, at each of these forty stations at eight in the morning. In the event of there being any storm or other atmospheric disturbance at one or more of these places, a full and accurate description of it is thus conveyed to London; and it is thence the duty of the officials there to consider the direction in which the storm is moving, so as to enable them to give warning of its approach by special signals. But in addition to warnings of storms, Fitzroy also issued daily "forecasts" of the weather likely to occur in the different districts of Great Britain for the following two days, and which were in like manner founded on the state of the atmosphere at distant points, keeping in view the atmospheric currents known generally to prevail at that particular time of the year. As the cost of this system was about £2000 annually, a severe test was applied, at the instance of the Treasury, from July 1861 to June 1862, for the purpose of ascertaining whether the expenditure was justified by the success attending it. During the first six months, 413 signals were hoisted, and in 214 cases a storm occurred where a warning was given. It must not be inferred that in the remaining 199 cases there was no storm anywhere; all that was meant was, that no storm occurred at the places where the signal was given; but a storm may have occurred, and probably did occur, in some other part of the country. Now that the system has been longer in use, the signals are given from a better knowledge of the movements of the atmosphere, so that if the test were again applied, the number of failures would be found to be much fewer. Since the barometric depression is in almost all cases spread over a wider area than the storm which accompanies it, and since the storm occasionally passes into the upper regions of the atmosphere, so as to be less felt on the earth's surface at that place, it is obvious that a considerable time must yet elapse before a sufficiently intimate knowledge of the movements of the air be acquired in order to indicate with certainty the particular places where the storm will break out, and where it will not. The problem to be practically worked out is this: Given the telegrams from the stations showing the exact meteorological conditions prevailing over the included area, with indications of a storm approaching in a certain direction, to determine, not the probable area over which the tempest will sweep, but the precise localities which will altogether escape, the places where the storm will rage, and the places where it will not touch the earth, but pass innocuously into the upper regions of the atmosphere; its continuance, its violence, and the particular directions from which the wind will blow at the places visited by the storm while it lasts. Considerable progress has already been made towards the solution of this difficult problem; and if a complete solution be impossible, such an approximation to a solution will doubtless be arrived at as will render it foolhardy to disregard the warnings given. But these predictions only extend to a few days. Does the present state of the science afford any grounds to hope that prediction for longer periods will yet be attained? Weather-registers extending over long periods give no countenance whatever to the notion, that there are regularly recurring cycles of weather on which prediction may be based. Further, the manner in which good and bad seasons occur in different places with respect to each other, shows clearly that they have little direct immediate dependence on any of the heavenly bodies, but that they depend directly on terrestrial causes. Thus, while the summer of 1861 was almost unprecedentedly wet and cold in Scotland, the same summer was hot and dry to a degree equally unprecedented on the continent of Europe, and particularly in Italy; and such examples may be multiplied almost ad infinitum. The assumption that the equatorial and polar currents of wind at any locality may Meteorology. ultimately balance each other, would appear, from recent observation, to give some ground for prediction extending over considerable intervals. Thus, a wet summer was predicted for Britain in 1862, from the circumstance of a most unusual prevalence of e. winds in the spring of that year. An almost incessant continuance of s. w. winds followed, which discharged themselves in deluges of rain, clouded skies, and a conse quent low temperature. As these s. w. winds prevailed till the spring of 1863, less s. w. wind was looked for during the summer, which was thus expected to be fine and warma prediction which was realized. This prediction holds in about three cases out of four. The following are a few standard works on Meteorology, in addition to those already referred to: L. F. Kaemtz's Meteorology, translated from the German (Lond. 1845); Dr. Erust Erhard Schmid's Lehrbuch der Meteorologie (Leipz. 1860); Professor Espy's Fourth Report on Meteorology (Washington, 1857); Drew's Meteorology, a useful handbook (Lond. 2d ed. 1860); Herschel's Meteorology (1861); D. P. Thomson's Introduction to Meteorology (1849); Buchan's Handy Book of Meteorology (1868); Loomis' Treatise on Meteorology (1868). METEOROLOGY (ante). The advancement in meteorological science in recent years has been mainly in the direction of the application of the laws of storms to practical use, in foretelling perturbations in the interest of commerce and navigation. In this direction great progress has been made, as to which, see SIGNAL SERVICE OF THE UNITED STATES. From the accumulation of statistics and history in this department, the following information concerning the government and private machinery for meteorological observation in different countries, is compiled: The first international meteorological congress occurred at Vienna, in September, 1873, when eighteen governments were represented by delegates officially appointed. This congress had been preceded by the Brussels maritime conference in 1853, the conference at Leipsic in 1872, and the meeting at Bordeaux in the latter year. The object of these meetings was to establish an international and reciprocal meteorological system for the benefit of the countries participating, and indeed of the civilized world. This object was so far effected that a strong interest was awakened in the subject on the part of the different governments, and a permanent committee was appointed which holds annual meetings. Among those-and chief among them-who have labored unselfishly to awaken interest in the study of the laws of storms should be ever remembered the names of Redfield, Espy, Fitzroy, Reid, and Maury; besides Humboldt, Dove, Ritter, Sabine, Kämtz, and Herschel, who preceded them in the same field. Through the efforts of some of these meteorologists the information gained by the experience of navigators has been collated and analyzed, and a very complete knowledge of ocean meteorology has been obtained; while the storms of the Indian ocean and the law of cyclones have been studied by Meldrum, with the assistance of the Mauritius meteorological society, to the great advantage of the world's information on the science. The first effort in the direction of making regular meteorological observations in the United States was made in 1818 at military posts, under the direction of surgeon-general Lovell, and as these are still continued, they form the oldest unbroken national series of the kind in existence. Certain of the states afterwards entertained the idea, and New York from 1825-1863, Pennsylvania 1836–1842, Ohio in 1842, and Illinois in 1856, formed organizations for the same purpose, but which have all been discontinued. Besides the information obtained from these sources, there has been much service performed in a desultory way by the Franklin institute, Smithsonian institution, state boards of health, agricultural and geological societies, and other organizations, as well as by special expeditions. Half a century ago, James P. Espy, an enthusiast, as well as a clear-headed observer, devoted himself to the study of meteorology, and by lectures and writings sought to popularize the subject. In 1836 he wrote a memoir which gained for him the Magellanic premium awarded by the American philosophical society; and in 1841 appeared his Philosophy of Storms, which publication completely revolutionized the sum of scientific opinion on the subject. The following year he was appointed meteorologist in the surgeon-general's office of the war department, and having already begun the practice of weather-mapping, he continued it daily. His first published report in 1843 is acknowledged to have been " by far the most important contribution to our knowledge of storms that had then been made by any government in the world." This was in 1843; and on Mr. Espy being transferred to the navy department, he published two other reports, dated 1849 and 1851 respectively. His fourth report was made to the U. S. senate in 1854. Mr. Espy died in 1857, at the age of 72, having devoted forty years of his life to meteorological study and investigation. Thus much is here given concerning this remarkable man, because of the influence which he exerted, and which doubtless gave the timely impetus that resulted in placing the United States in the front rank among those nations that have given its due importance to the study of meteorology. This study, with its accompanying record of observation, is prosecuted in the United States at the following points, 1. The independent observatories at Cambridge, Washington, Albany, and New York Central Park. 2. The state weather services of Iowa, receiving reports from 80 observers; Missouri, with 100 observers; and Nebraska; which all publish monthly reviews and annual reports. 3. The state boards of health for Michigan, New Jersey, etc. 4. The state boards of agriculture for Illincis, |