Popular Science Monthly/Volume 16/January 1880/The International Weather-Service
By Professor T. B. MAURY.
THE "weather" is that mystic word which sums up the physical influences most affecting the human frame for good or ill. The splendid, ever-varying panorama of the sky, the benign mutations of the seasons, the immense pulsations of the atmosphere furnished, however, for ages, themes for the poet rather than for the philosopher. In the presence of its tremendous though cloud-veiled forces, as the high priest of old on the entrance of the sanctuary, we tread with awed footstep. From time immemorial its phenomena have engaged the daily and deepest attention of men; and the ever-popular, ever-compulsory study of their changes, in the language of all civilized nations, has been called "meteorology," which literally means "the science of the sublime." "Distance and time," says the physical geographer Ansted, "seem annihilated when we watch the action of these mysterious influences, and we may almost recognize the reality of an existence unhampered by natural impediments when we find an instantaneous response of our innermost senses to a material stimulus applied within the burning atmosphere of the sun." But the overmastering interest and awe, awakened by the terrestrial atmosphere, through which this stimulus reaches us, are intensified by the consciousness that upon it we depend for vital breath, and that it is the medium through which an invisible hand sweeps every chord of humanity.
It is to that grand and systematic investigation of this physical agent, which has recently been commenced by the concert of the nations, in a system of world-wide "Simultaneous" observations, known as The International Weather-Service—to its history, methods, and utilities—we would now direct the reader's indulgent attention. fore doing so, however, it will be necessary to glance at the advances in weather-research that have led to this undertaking.
The exploration of the vast body of water which surrounds the land-masses of the globe has been, since the sixteenth century, rapidly prosecuted. Its configuration has been determined, its tides have been weighed, its gulf-streams and counter-currents gauged, and even its abyssal depths sounded and surveyed, until we can now hardly speak, save by poetic license, of "the dark, unfathomed caves of ocean." But the exploration of that other and almost boundless ocean of air which envelopes the whole earth and whose winds sweep its surface, swaying the waters of the sea and affecting every form of terrestrial life, has progressed but slowly. The upper atmosphere is pierced by but few of the earth's mountain-peaks upon which meteorological stations can be efficiently maintained, while the spasmodic attempts at aeronautic investigation of the cloud-land, daring as they have been, have realized less knowledge of its currents than that which Columbus in his voyages of discovery acquired of the circulation of the equatorial waters. Investigation has been, therefore, perforce restricted for the most part to the phenomena of storms, cyclones, and anti-cyclones, moving at the bottom of the great sea of air--phenomena involving such insignificant portions of the atmosphere, when compared with the superincumbent mass, that a leading meteorologist has hyperbolically likened them to ordinary "smoke-rings." Even in the lower atmospheric strata, the different national bands of observers have been widely separated--here and there an ocean unsentineled rolling between them--so that their collated reports conveyed no clearly connected account of the transcontinental movements of air; and it is to-day disputed by some that North American storms cross the Atlantic to western Europe. But, worse than all else, the observations taken by the most painstaking and indefatigable observers were, until recently, systematically vitiated, not only by a lack of uniformity in the methods, but by the more fatal lack of uniformity in the hours of observation. What would be thought of a little army confronting immense odds, some of whose regiments had one plan of battle and some another, some asleep when others were engaged, but none acting simultaneously? Yet, such is a fair representation of the world's observational force which was expected to attack the great problems of meteorology, as it was until less than a decade ago.
In 1870 the United States entered the field of weather-research; and, for the first time in the history of meteorology, there was then established a broad system of simultaneous observations and simultaneous reports of the weather. These reports were immediately worked up and graphically embodied in the simultaneous weather-maps, issued thrice daily from the office of the Chief Signal-Officer, U. S. A., General Albert J. Myer, whose original and announced plan was to observe the weather over the whole country "at the same moment of actual (not local) time," as was stated on every weather-map. This conception aimed at the rescue of meteorological researches from that disorder and disconnectedness which had always characterized the observational work. The prime object was to gain a daily conspectus of the atmosphere over the country as it actually was, and as it would be seen if a photographic view of it, so to speak, could be taken. The simultaneous method, when announced, seemed so natural and simple that one might have wondered that any other was ever attempted. Observations called "synchronous" had been, indeed, before this time, energetically made in several countries; but the term "synchronous" was used to signify that every observer read off his instruments at given hours of his own local time, and not at the same moment of physical time. Etymologically, there might be little or no difference between "synchronous" and "simultaneous," but, for all the purposes of atmospheric investigations over a vast territory like that of the United States, the practical difference was by no means insignificant. When observers, who on the old "synchronous" method reported the weather-status each at the same hour of local time, were separated by hundreds of miles, their reports failed to represent the actual fluctuations of the atmosphere and the true bearings of its cyclonic and anti-cyclonic movements; so that, when the meteorologist came to compare and chart the combined data, they yielded necessarily a distorted or untrue picture of the ever-restless aerial ocean. On the other hand, in the "simultaneous" method, since all the observers over the wide field of the research read their instruments at one and the same moment (7.35 a. m. Washington mean time), their reports, when charted, gave a true and life-like representation of the physical phenomena as they actually coexisted and conspired. As on the screen of the artist's camera the sun instantly paints the true image of the human face before its expression can be changed, so does the process of simultaneous observation seize and secure all the elements necessary to delineate the current physical features and conditions of the atmosphere, as existing at d, fixed moment, and before they can have time to undergo change. Simple as this expedient is, it is evidently the key to all effective research in a vast gaseous ocean whose currents and waves are ceaselessly rolling and rapidly altering their geographical bearings, even while the sun is quickly passing from one meridian to another. Were all the weather observers of the world to read off their instruments as it were by a given tick of one clock, their collective data would furnish materials for the most exact delineations of the complex atmospheric machinery which it is possible to obtain. Instead of piling up a mass of weather bulletins unsuited for purposes of a rigidly scientific inter-comparison, as was so long done, they would contribute solid and coherent facts of nature, all ready to be put together and worked up by the meteorologist into a noble and useful science.
Having noticed the first attempt ever made to establish a system of "Simultaneous weather-reports," and indicated the unique character of the system, as carried out by the United States since 1870, we hasten on to the history of its extension to the vast field of international meteorology. In September, 1873, the International Meteorological Congress was convened at Vienna, to consider all the graver questions that were then agitating public and private investigators, as to the progress of weather-science. The Congress was composed of official representatives, charged with the meteorlogical duties pertaining to the researches of their respective Governments. It was then proposed by the representative of the United States, General Myer, that it is desirable, with a view to their exchange, that at least one uniform observation, of such character as to be suited for the preparation of synoptic charts, be taken and recorded daily and simultaneously at as many stations as practicable throughout the world." This proposition was unanimously concurred in, and its hearty adoption by the Congress, the members of which virtually legislated for the nations they represented, at once secured the extension of the American "simultaneous" system (as inaugurated in 1870 for the United States) to the entire field of weather investigation then covered or yet to be covered by the observers of all the nations. Soon after the adoption of this proposition at Vienna, by the courteous cooperation of scientific men and the chiefs of the meteorological weather-bureaus of the different countries, records of uniform observations, taken daily and simultaneously with the observations taken over the United States and the adjacent islands,
were commenced, and since then have been exchanged in semi-monthly communications. These reports, steadily increasing, now cover the combined territorial extent of Algiers, Australasia, Austria, Belgium, Central America, China, Denmark, France, Germany, Great Britain, Greece, Greenland, Iceland, India, Italy, Japan, Mexico, Morocco, the Netherlands, Norway, Portugal, Russia, Spain, Sweden, Switzerland, Tunis, Turkey, British North America, the United States, the Azores, Malta, Mauritius, the Sandwich Islands, South Africa, South America, and the West Indies, so far as they have been put under meteorological observation. On July 1, 1875, the daily issue of a printed bulletin, exhibiting these international simultaneous reports, was commenced at the Army Signal-Office in Washington, and has since been maintained. A copy of this "International Bulletin" is furnished each cooperating observer. This publication combines for the first time of which we have any record the joint labors of the nations in a research of this kind for their mutual benefit. As the network of cooperating stations already spreads over so vast a proportion of the land-surface of the globe, there is needed only the more general cooperation of the naval and merchant fleets of the world to supply ample data for a comprehensive study of the atmosphere as a unit. This need is now growingly appreciated, and nine series of marine reports, each containing the simultaneous observations of a number of sea-going vessels, have been added to supplement the similar reports contributed by the land-observers, swelling the total observational force to 500 laborers. The harvest of physical data already garnered by this force, and daily increasing, will be invaluable for all future weather investigations. As the Committee of the Scottish Meteorological Society recently said, "This truly cosmopolitan work, which the United States are alone in a position to undertake, thanks to the liberality and enterprise of their Government, will bring before us month by month the general circulation of the earth's atmosphere, and raise if it does not satisfy many inquiries lying at the very root of meteorology, and intimately affecting those atmospheric changes which meteorologists have been recording." It will greatly enrich the meteorology of the ocean and aid navigation, by supplying data for deducing those true mean physical values which teach the mariner at sea where he may find "a fair wind and a favorable current," how he may best utilize the forces of nature and elude its terrors. It will afford material for the renovation of the climatology and sanitary meteorology of regions not now fully investigated. But, above all, it will facilitate the elucidation of the laws of storms and those associate phenomena which conspire to produce the many-colored phases of "the weather."
The cardinal object of this vast scientific enterprise, as the reader may anticipate, is the study of the atmosphere as a unit. The atmospheric ocean must be viewed by every thinking mind as a whole, whose complex parts act interdependently—as the various parts of a steam-engine—yet all constituting one grand mechanism. Nature's forces respect no national frontiers; and, if their mighty play is to be watched by science, its observational corps must be expanded to cover every accessible part of the globe. This will be made more apparent if we consider the intensities and movements of cyclones. The storms generated over the sea often push with resistless energy against the loftiest mountain-walls, and, surmounting their acclivities, press on as if they had felt no retardation, to sweep across an entire continent, and then, untired, to take a fresh start on a long ocean-voyage. In a rigid examination of the Signal-Service data for a period of twenty-six months, twenty-eight storm-centers, it was found by Professor Loomis, traveled eastward across the Rocky Mountains, and reached the Mississippi Valley in unimpaired vigor, having scaled that imposing barrier, 10,000 feet high, as easily as the steamship on its rapid course overrides a wave. In discussing the two cyclones which visited the Bay of Bengal in October, 1876, Mr. Elliott, Meteorological Reporter to the Government of Bengal, incidentally gives us some idea of the cyclopean forces which are developed by such storms. The average "daily evaporation," registered by the Bengal instruments, in October, "is 2 inches." The amount of heat absorbed by the conversion of this amount of water daily over so large an area as the Bay of Bengal is enormous. "Roughly estimated," says Mr. Elliott, "it is equal to the continuous working power of 800,000 steam-engines of 1,000 horse-power." A simple calculation will show that it
Vertical Section of the Heat of a Cyclone. (Arrows show direction of wind and the ascending current in storm-center; the dark-shade, nimbus, or rain-cloud.)
suffices to raise aloft over 45,000 cubic feet of water in twenty-four hours from every square mile of the bosom of the bay, and transport it to the clouds which overhang it. When we extend the calculation from a single square mile to the area of this whole Indian gulf, the mind is lost in the effort to conceive the force which, in a day's time, can lift 50,000,000 tons! Yet, it would be easy to show that such figures, fabulous as they seem, do not adequately represent the cyclonic forces of a single storm. "The usual size of the cyclones in the Bay of Bengal," according to Piddington, "is from 300 to 350 miles; but," as he adds, "it would appear that they sometimes much exceed that extent"; and others give the average diameter as still greater than 350 miles. Now, in the passage of a cyclone over such a sheet of water, the vapor which has been slowly generated over its surface for many days is rapidly condensed and reconverted into water, and falls in the shape of torrential rains—as Dampier declared, "faster
Horizontal Movements of Air Around Center of Cyclone in Northern Hemisphere.—(Large arrow shows path of storm: smaller arrows, the winds taking a more radial direction, and increasing in velocity, as they near the center.)
than he could drink it." On the coasts of India, twenty inches have been known to fall in a single night; in the Bengal storm just mentioned, 15·2 inches fell in eighteen hours. Assuming that the mean daily precipitation within the areas of storms like those just referred to is only three inches, it is evident that Mr. Elliott's calculation of the mechanical force daily exerted in the work of evaporation falls short of expressing the force exerted in the work of precipitation during a day's march of a cyclone. The latter is, however, but one of the many tremendous agencies engaged in the development of a storm of ordinary magnitude in the intratropical regions. In the extratropical and high latitudes, cyclones are much more extensive, "being seldom less than 600 miles in diameter, but oftener two or three times that amount, or even more" (Buchan); while the waves of the sea, driven by their winds, beat upon the seacoast, as Mr. Stevenson, the well-known English engineer, has estimated, with the almost incredible force of "6,000 pounds on the square foot." In the hurricane of last August, the winds on the North Carolina coast blew at the rate of from 138 to 165 miles an hour.
In citing these illustrations of the storm-phenomena which modern meteorology is charged with investigating, we have not alluded to the equally important yet far grander phenomena of "anti-cyclones," or those "atmospheric waves" of high pressure which, emanating from the higher latitudes, submerge a whole continent at once--around whose borders cyclones move as diminutive eddies playing around a rock in mid-stream. But enough has been said to show the imperative necessity for the prosecution of wide-extended or international research.(including of course oceanic observations) if the laws of weather are ever to be discovered and defined. In no branch of physics is it so true, as in that of weather-lore, "a little learning is a dangerous thing." An approximation to the conception and study of the atmospheric machine as a unit is the sine qua non of all future advance in this knowledge. Phenomena such as we have just glanced at, by their immensity and by the intensity of the forces which resistlessly propel them across seas and continents, will for ever defy adequate investigation, save by an army of observers, acting simultaneously, both on the ocean and on the land, whose outposts stretch from the rising to the setting sun and from the equator to the polar circle. For, as another has so forcibly and felicitously said: "The atmosphere, unlike the ocean, is undivided and uninterrupted; and every change of state, in any part of its expanse, sends forth a pulsation of energy which is speedily felt far and wide." If the oracles of Him by whom are all things declare that he spreads "the cloud of dew in the heat of harvest," who "gathereth the winds in his fists," and once hushed the roar of the Galilean tempest, well may these wonders, ever fresh from his hand, enlist the earnest and inspiring study and observation of intelligent men everywhere. Our favored planet, not like the airless moon, is folded in the kindly bosom of an atmosphere which, while ministering nourishment to man and accommodating itself to all his movements and vicissitudes, interposes as his shield against the fiery influences of the solar system, even to arresting and consuming those countless meteoric stones, showered upon us from stellar space, before they can penetrate to the lower aerial strata. For us, at least, in respect to this sublunary scene, it is of engrossing interest, as that all-pervading organism which
"Lives through all life, extends through all extent,
Spreads undivided, operates unspent."
In the technical execution of this purely pioneer work, the first step was the preparation of a daily graphic and synoptic chart exhibiting all the weather observations taken simultaneously in the northern hemisphere. On the 1st of July, 1878, the Signal-Office at Washington began the regular publication of a daily international weather-map, charted daily and issued daily, each chart being based upon the data appearing in the "International Bulletin of Simultaneous Reports" of similar date. The daily issue of a weather-chart of this kind and scope is without a precedent in history. It illustrates the cooperation, for a single purpose, of the civilized powers of the globe north of the equator, and brings the atmospheric phenomena over the whole field of the research, and in their true relations to each other, within the easy comprehension of the student's eye. (See frontispiece.) As these charts in successive order are spread out day after day, the investigator has before him a vivid panorama of the physical forces in pictured action, so that he can readily trace their mutual dependence and interaction in the normal working of the ponderous, yet beautiful, atmospheric machinery.
The history of progress in the discovery of physical phenomena and their laws is intimately connected with the introduction of technical contrivances so simple that at first they attract little notice. After the invention of the mariner's compass, and the astrolabe, nothing perhaps that was done for geographical science gave it such an impulse as the chart introduced in 1556 by Gérard Mercator, by which the earth's entire surface was presented in a single picture to the geographer's eye, and by which (the degrees of latitude and longitude at all places bearing to each other the same relations they bear on the sphere itself) the navigator could readily steer his ship in straight lines. This simplest of contrivances became, in a word, an invaluable instrument of maritime exploration and discovery, the present and almost exclusive employment of which by mariners of all nations, as the chart for the ocean, has brought the name of Mercator down to this day in honored remembrance. Not to dwell upon the charts of Paolo Toscanelli in the fifteenth, and of Martin Behaim in the sixteenth century, so justly celebrated--the former as guiding Columbus on his great west-ward voyage, and the latter as blazing Magellan's perilous way toward the southern shore of South America, to circumnavigate the globe--we may well say, "Accurate maps are the basis of all inquiry conducted on scientific principles." The "International Weather-Map of Simultaneous Observations" is a generalization in itself, and offers the meteorologist every day a bird's-eye view of the aërial world as it actually was at that fixed moment of physical time when all the observations embodied in it were made. Nothing can be simpler or more intelligible to even unscientific eyes than a chart which, by means of suggestive symbols, displays the different elements of the weather over a hemisphere, each in its own color. Just as Mercator's projection represents the entire ocean to the mariner—as if there were no horizon or sphericity—and all objects in their true meridional bearings to each other, so the "International Weather-Chart" depicts the aerial ocean in its beautiful integrity and all its parts in their true physical relations to each other, as certified by strictly simultaneous reports. Of course, the two charts are entirely independent and different; but we refer to the invention of the old Flemish geographer merely to illustrate and enforce the immense value of every really synoptic chart as a weapon of research and as a medium of scientific discovery.
The cartographic method, by which truly synoptic views of the atmosphere are obtained, is indeed the natural accompaniment and handmaid of the method of "simultaneous weather-reports," both of which are peculiar to the national weather-service inaugurated at Washington in 1870, and, through the adoption of General Myer's proposition at Vienna, in 1873, extended to the new international weather-service. Without "simultaneous" weather observations, it is obvious, no truly "synoptic" weather-chart is possible; and, as has been said, the first "simultaneous" observations were those instituted by the United States in 1870, The unique and novel feature of the international weather-charts, and the feature which will most commend them to meteorologists, is that they furnish a faithful pictorial history of the atmosphere and its revolutions, enabling the inquirer to trace its currents and counter-currents, to witness the behavior of its cyclonic storms and other barometric waves as they traverse continents and deploy upon the ocean, and to form clarified conceptions of its massive yet orderly machinery. The well-known English journal of science, "Nature," "earnestly hopes that the navies and the mercantile vessels of all nations will soon join in carrying out this magnificent scheme of observations, originated by the Americans in 1873, and since then further developed and carried on by them with the highest ability and success." Its French namesake, "La Nature," said recently, when speaking of this service, "One ought not to be surprised to learn that the United States, encouraged by their first successes, are to attempt a new extension of a system of observations which has already, in so few years, produced considerable results." It would not be an easy task to predict the future results to be obtained by such a system of investigation; but we may confidently conclude that no system of weather inquiry ever before undertaken promised a richer harvest of meteorological lore than that which rigidly follows up its simultaneous observations and amasses its corresponding charts. Every cooperator in the work, it should be added, is encouraged and stimulated by the fact that a daily copy of both the "International Bulletin" and "Chart" is furnished by the United States, without cost, to each observer, on land or at sea, of whatever nation, who, at the request or with the sanction of the Chief Signal-Officer, cooperates in the enterprise.
We come now to the question of the practical application and utility of the data and charts published in connection with the international weather-service. And here the embarrassment arises from the multiplicity of matters, affecting almost every interest and industry of mankind, upon which this service will bear. There is not a profession, or trade, or handicraft in society which is not at every turn more or less influenced by the weather, and compelled to act upon some kind of weather-forecasts. No sooner had the Weather Bureau commenced its daily publication of "Probabilities" or "Indications," in 1870, than "whole troops of practical applications" of the data sprang into existence. It will be so with the international bulletin and charts of simultaneous meteorology.
One of the first practical applications of the simultaneous observations over the northern hemisphere will be realized in the elucidation and correction of "the law of storms," and of the rules for the extrication of ships from the storm-vortex. Great have been the intellect and learning employed in the settlement of this question, so important to commerce and navigation. The time-honored researches of Redfield, Reid, Espy, Piddington, Thom, and others of the past, supplemented and harmonized in a measure by those of living laborers in the storm-field, have indeed established the existence of a "law of storms" upon an unassailable foundation. But they have not defined some of its cardinal conditions. The definition of storms as "revolving gales," in which the winds blow in concentric circles around a calm center, has been rudely damaged by the facts every day brought to light. And the contrary theory, that the storm-winds blow in radial lines toward the vortex, has not fared much better. The intermediate hypothesis, that the winds blow in regular spirals around the center, while it apparently reconciles some of the otherwise conflicting facts, and has given a temporary quietus to the storm controversy, strictly speaking, is not less objectionable than either of the theories it affects to correct: for it apparently obliterates, or seemingly ignores, the two large and distinct classes of indisputable wind-phenomena upon which the rival deductions of Redfield and Espy were respectively based. Time has fully demonstrated the insufficiency of both the "circular" and the "centripetal" theory to account satisfactorily for all the salient and phenomenal features of a cyclone, but it has attested the immense value of them both as scientific approximations to the truth. But, it must also be said, the theory of "spiral" currents arranged symmetrically around the storm-center does not furnish a complete solution of the problems raised by a study of cyclone observations. In the domain of practical "nautical meteorology," and in its applications to the handling of ships on the outer circles of revolving gales, it is especially yet to be sifted in the light of the most exact "simultaneous" observations. The international weather-charts, illustrating the exacter forms of marine storms, show us that they assume very eccentric shapes (see chart, p. 305), and consequently develop variant wind systems. On the liquid expanse of the stormy North Atlantic, crowded with the steamers and sailing-ships of all nations, there exists the finest field for this investigation to be found on the globe. When these vessels become "floating observatories," rendering up accounts of their daily simultaneous weather experience, it will be comparatively an easy matter to set for ever at rest the yet disputed questions of the phenomena of cyclones, and to formulate rules for maneuvering ships so as to elude their crushing forces.
Manœuvering Ships on the Exterior of a Cyclone. (The dotted lines Aa, Bb, Cc, Dd, and Ee show the paths of escape from (dangerous positions; the large arrow, the storm's progressive direction; the small arrows, the cyclonic winds.)
The birth, life, and death of storms; their translations from continent to continent, with the times and directions they take in such transits; the thermometric, baric, and wind conditions around the globe at various parallels; the distribution and amount of rainfall and snow-fall; the laws of our great "hot waves" and "cold waves," with many other data for settling questions of climatology, and possibly of forecasting in some degree the character of coming seasons--are some of the problems of every day's life which the international charts and bulletins will serve to simplify or solve. Among these, none perhaps calls for an earlier and exacter solution than the translation of cyclones from the Asiatic waters over the forth Pacific Ocean to the Pacific slopes of the United States, and the kindred question of the transatlantic passage of American storms to western Europe. As we have already seen, so far as critical examination has been made of the Signal-Service weather-maps, more than one cyclone from the Pacific coast every month, on an average overleaps the Rocky Mountains and travels eastward, reaching the Mississippi Valley and the Lakes, with its original (perhaps ocean-born) strength. The ocean is preeminently the birthplace and habitat of storms. Thence when fully formed and densely stored with aqueous vapor--the fuel of the cyclonic engine--they assail the land-masses of the earth, and traversing them, unless in transitu, they perish for want of water, and turn to their native element. This is no less true of the Great Ocean that washes our Western shores, notwithstanding its name, than of the "stormy Atlantic." Uncomfortably near as the West Indian hurricanes approach our Atlantic seaboard, they affect but comparatively a small strip of the Eastern half of the United States, and often give us a wide berth. But the storms which invade our Pacific seaboard, from southern California to the mouth of the Columbia River, exert or expend their full force within the national limits and frequently cut their broad swaths entirely across the country. The golden key, therefore, to our continental meteorology is the adequate knowledge of the barometric depressions and associate "waves of high pressure" which roll over the continent from the westward, and in their progress dominate the weather to the north of the thirty-fifth parallel.
Off the California coast there exists, throughout the year, a permanent area or wave of high atmospheric pressure, or a vast "anti-cycione"—the diameter of which is something like one thousand miles. The barometer in this area reads 30·20 inches (see chart, p. 309). From its northern and western slopes, westerly and northwesterly wind-belts extend in an easterly direction across the Coast and Rocky Mountain range. The immense stationary anti-cyclone, from which flows off this broad belt of westerly winds, is probably due to the continental barrier arresting and accumulating the perennial equatorial current from the central zone of the Pacific Ocean; and has its counterpart in the similar area of high pressure lying in the Atlantic, off the coast of Spain and south of the Azores. The great highway therefore, along which the chief atmospheric currents move and introduce on our continent the storm-controlling and weather-producing influences, begins on the Pacific coast and traverses the country from west to east. As the Atlantic dominates the weather of Europe lying on its eastern shores, so in the Pacific Ocean is the cyclopean workshop of the atmosphere, in which are produced and whence are sent forth the meteors that perpetually travel over North America, and substantially mold its climate and weather. To cover the North Pacific, therefore, with a network of "floating observatories," contributing their "simultaneous weather-reports" to the Signal-Service Bureau, is one of the grand desiderata of American meteorology. A ship at sea is one of the best of stations for a simultaneous meteorological system. The value of its records is enhanced by the considerable change of the ship's location occurring once every hour; and the law of self-interest at least should compel every ship owner and shipmaster to enlist in a joint observational work which inures to his own safety and lends a helping hand to every meteorologist. Without the data, to be collected only by vessels sailing on the North Pacific, the prevision and prediction of storms and weather-changes that transpire in the Pacific and Western States, and are thence propagated to the East, can not be put upon a sure footing. With such marine simultaneous data, the work of weather-forecasting and storm-warning for the Pacific coast and the whole country will be greatly simplified, and the accuracy of the work much enhanced, if not assured. If the solar light of day comes first from the East, we may nevertheless predict that the flood of scientific light necessary to elucidate the still obscure phenomena of American, and especially Western meteorology, will break upon us from the Great Western Ocean. "The improvement" in the national tri-daily "Indications," etc., of the Signal-Service, which General Myer hopes for, as his oceanic simultaneous work "progresses," can not be doubted.
If anything more is needed to enforce this view of the immense value of North Pacific researches for the development of American weather-telegraphy, it is found in the fact that the cyclones of that ocean recurve from the Asiatic coast, and follow the warm current known as the "Kuro Siwo," or "Japan Current"—the congener of our Atlantic "Gulf Stream"—in its northeasterly extension to the northwestern coasts of the United States. This mighty "river in the sea" is a natural storm-channel. "The influence of the Kuro Siwo," says Captain Silas Bent, the original and careful investigator of its phenomena, "upon the climate of Japan and the west coast of North America is, as might be expected, as striking as that of the Gulf Stream on the coasts bordering the Atlantic." And Kerhallet, the well-known French hydrographer, tells us that it "crosses all the northern part of the Pacific Ocean, and makes itself felt on the northwest coast of America." "The track of typhoons in the China Sea," according to one of the highest nautical authorities, Labrosse, "lies between north-northwest and south-southwest, then toward the north, and afterward turns sharp around toward the east, in the direction of the Bashee Islands," whence in 1854 Mr. Redfield traced a number of them far away toward the American coast. These terrific rotatory gales rival, if they
do not exceed, in intensity, the fiercest Atlantic hurricanes. The cyclone or typhoon of the U. S. steamship Mississippi, October 6, 1854, with that of the U. S. storeship Caprice, and the steamship Susquehanna, July 17 and 19, 1853, in Commodore Perry's Japan Expedition, are among the most memorable storms of history on any sea, and illustrate the magnitude and might of those atmospheric forces so characteristic of the Great Ocean, whose meteorology is now to be brought under strictly simultaneous surveillance and studied in its close causal connections with that of our own country.
As the investigation of the Pacific's meteorology is so important to America, the same system of observations applied to the Atlantic reaches to the roots of European meteorology. It is well known that the atmospheric conditions which shape European weather and climate are propagated over the French and British coasts from the Atlantic, so that every intelligent storm-warner and weather-forecaster in Europe casts a wistful eye to the western waters to catch some premonition of what is to befall his coasts. Propositions to buoy in the mid-Atlantic ships, equipped with self-registering barometers and weather-indicators and connected by telegraphic cables with the shore, which would flash reports of precursory changes to the central Signal-Office, were suggested by General Myer to meet a deeply-felt need. It has also been very seriously proposed to dispatch carrier-pigeons by the westward-bound English steamships, to bear back weather-reports from points two hundred or more miles at sea, in the hope that the London office might have data for more timely weather-warnings. "It is possible," says the Russian meteorologist Wœikof, "that in October Atlantic storms may reach as far as Yakutsk" (in northeastern Siberia) which is farther from the Atlantic than England is from the Pacific Ocean. "In Europe," Mr. Buchan tells us, "stormy weather is accompanied by a diminution in the atmospheric pressure, the center of which, after traversing more or less of the Atlantic, arrives on the coast of Europe." One weather-report from the Atlantic, if only made a few hundred miles from the British coast, would be worth, for all practical purposes of storm-prediction, more than dozens of continental reports. If, indeed, the international system does not supply the needed ocean-reports in time for the European work of daily storm-warning, its daily charts show the conditions which usher in the various weather-changes upon the European coasts. They show, moreover, the tracks which, at each season, Atlantic cyclones are wont to select and pursue as they approach Europe, and the rates at which they traverse these tracks. Given these mean data, deducible from the international weather-charts, and the chief elements are had for deciding any special question of weather that arises in the daily work of forecasting. As a late writer says: "The most abstruse discussion of meteorological data have hardly another object than the determination of the average conditions of the climate of each place, and of the amount of variability which may be anticipated in the march of each element. What is this but forecasting?" Every increase of simultaneous reports is, therefore, another approximation to that knowledge which would, if sufficiently full, enable the European meteorologist to foresee
A "Low Barometer," or Cyclone, crossing the Atlantic prom America to Europe. (From "International Weather-Map," February 9, 1878.)
and to give every day more timely forewarning of impending variations in the weather and "the march of each element." But this is the grand end which all such international research contemplates. "From the use of synchronous weather-maps," another prominent English meteorologist tells us, "there has sprung up in recent years a new science of the winds. With the principles of this science all the more reliable rules of weather-forecasting are most intimately connected. We no longer think of judging of coming weather merely by the aspect of the sky and an examination of an individual barometer. We invariably refer—I do not say to the weather-reports of a few hours previous, for we often have neither these nor any weather-reports at all at hand—but we invariably refer to rules already deduced from the long study of weather-maps. The man who ignores these rules had better, in my opinion, leave all attempts at weather-forecasting alone. At best his weather-lore will not rise much above that of the bees, which fly to the hive, often to their own detriment, whenever a dark cloud covers the sun." We cite these words as expressive of the wise dependence which the most skillful European meteorologists put upon the weather-charts of the past. How much more light will they derive from the new international "simultaneous" weather-maps! While the scientific world is despairing of finding adequate mechanical means of mooring a floating weather-station in mid-Atlantic to cable its reports to land, the necessity for such a station is being gradually superseded by the development of researches which if studied will supply adequate rules for weather-forecasting without mid-Atlantic reports. The immediate value of every means which offers any approximation to correct storm-warnings for the British and French coasts—frequented by the navies and merchant marines of every flag—is beyond calculation in dollars and cents.
The ultimate value of the temperature and rainfall statistics obtained by this research, especially in their application to agriculture, can not be questioned. Even if such data were of no avail for the general work of weather-forecasting, they reach into the sphere of all farming operations, and are utilized by all classes. One of the most striking exemplifications of this fact has been furnished by Governor Rawson, of the island of Barbadoes, who, in an official paper, has used the rainfall reports "in calculating the probability, or expectation, of coming seasons as respects the yield of the sugar-plantations."
The long-protracted and often torrential precipitation that drenched the British Islands and large portions of western Europe last summer (1879), had been preceded by long-protracted and abnormal chilling of those countries, whose crops were blighted or dwarfed for want of sunshine and ruined by too frequent down-pours. Now, it is a fact worthy of deep reflection that on June 12th, before this dreary and desolating summer had set in, the English journal of science, "Nature," published a summary of thermometric data from ninety-two stations, which demonstrated that "the cold weather, for the six months ending May 1, 1879, exceeded in intensity" (that of) "any other past period of cold weather in these islands of like duration, of which we have an exact and authentic record." Great Britain on the 1st of May was then abnormally refrigerated; these islands, and we may add the adjacent continent, were ready to act as powerful condensers of the tropical and North Atlantic vapor wafted over them in enormous volumes by the southwest or "anti-trade" winds, which especially prevailed in summer. But more significant still were the barometric conditions prevailing over Iceland, which so greatly affected the weather of the British Isles. The spring of 1879 was unusually cold, and the international weather-charts, prepared by our Signal-Service, show unusually high pressures throughout April, 1879, over Iceland, just as occurred in July, 1867, when there was a memorably cold spell in Great Britain—owing to the fact, as Mr. Buchan explains it, that "the pressure being low in Norway and countries surrounding the Baltic, and high in Iceland, Scotland was thus placed in the cold Arctic current which set in from Iceland toward the Baltic."
Now, with such clear barometric and thermometric conditions in and around Great Britain, a "cold, wet summer" in 1879 was almost inevitable, and a prediction to that effect, based on the simultaneous international data, would have been justifiable. Of course, new conditions might arise late in June, but the conditions prevalent, according to all physical probability, authorized such a forecast at the commencement of the summer, and would have been of incalculable value. Ask the British farmer what he would have freely paid in June to have gained some idea of the July weather! Or ask the English merchant what he would have freely given in June for a tolerably correct crop-forecast for the summer of 1879! Yet this is no hypothetical case, but one familiar to all, involving a whole nation in agricultural and financial distress, against which, with international reports from the Faroe Islands and Iceland, it could have been forewarned.
The collection of the "international" cloud-observations—especially those taken at sea—opens one of the most fertile and fascinating fields, not only for the elucidation of the profoundest atmospheric problems by the theoretical scientist, but for the popularization of meteoric knowledge. The clouds are Nature's weather-guides, at all times serving to preannounce the approach of storms, or the return of clear weather. Until the middle of the seventeenth century (when Torricelli's experiments led to the invention of the barometer), and long after, the clouds furnished the only weather-indications which the world had. And, the more modern meteorology is developed, the more do the ablest of its leaders seek to understand these unerring monitors of every weather-change. Varied as they are, their forms may be reduced to two or three types, so defined and imposing that the most unscientific can learn to recognize them and construe their meaning. The international observers enter on their blanks the amount and direction of clouds, "The most valuable of weather-signs," says Mr. Ley, "are obtained not so much from the shape of the clouds as from the directions from which clouds of different levels are observed to travel, and it is these weather-signs which, in the present state of our knowledge, can be most readily reduced to definite rules."
Take a single illustration of the utility which such rules would have for the farmer, the sailor, or any close observer of the sky. Our storm-centers are generally preceded by a great bank of those clouds to which the name cirro-stratus is given. They are composed largely of freezing or frozen vapor, floating at great elevations, and often very far in front of the depression and over the belt of country which is to receive its rainfall. They move in parallel lines, and are distinguished by their thread-like and attenuated delicacy, as well as by their altitude—from 20,000 to 40,000 feet—from all local clouds. Outlying streaks of the cirro-stratus, frequently visible from twenty to one hundred miles in advance of the main pack, "like pioneers of the coming army," can easily be detected. But the main body, since it forms the familiar halo, can not be overlooked. It is the timely omen of impending disturbance, delivering its faithful warning long before the barometer begins to fall and tell its confirmatory tale. The accompanying cloud-illustrations, constructed, with some variations, after Mr. Ley's designs, will illustrate the chief weather-changes. Fig. 1 represents cirrus and cirro-stratus forming far in front of a cyclone, while yet the barometer has not begun to fall decidedly. Fig. 2 shows the cloud-system attending one of our storm-centers, as viewed from a point say 25,000 feet high (above the disturbance), the whole system borne along in the broad, horizontal "antitrade-wind" belt, from southwest to northeast, the scale of miles 200 to the inch, and the rate of progress fifteen miles an hour.
Could the rural populations and those whose occupation calls them much out of doors be assisted in interpreting these and similar phenomena, however untutored they might be in meteorologic terms and theories, they would soon learn to forecast many of the great weather-changes for themselves. But as the storm-signaling clouds, conspicuous to all, fly aloft in those mighty "upper currents" which, observation shows, attain not uncommonly velocities of one hundred and twenty and sometimes even one hundred and fifty miles an hour, none but strictly "simultaneous" weather-reports can adequately or truthfully reflect their actual, ever-flitting movements as related to storm-vortices and other atmospheric phenomena, whose approach and force they fore-token.
Once more. The most popular and profitable use to which meteorologic observations can possibly be put would be, if it is practicable, to forecasting in part the character of coming seasons—whether the next winter will be mild or severe, or the approaching summer wet or dry. It is certain that such forecasts will not be made until the network of observing stations is so enlarged as to record the temperature and other conditions over extensive portions of the oceanic, as well as the solid face of the globe. The northern hemisphere at least must be belted with stations returning simultaneous reports before season-predictions can be successfully attempted. But, with a broad girdle of observations around the middle latitudes, would it even then be possible to foreshadow the abnormal or extreme heat or cold of a coming summer or winter? It may seem premature to offer any reply to such an interrogatory; and yet it may not be as unanswerable as it seems. It is now pretty clearly ascertained that the earth in its orbital revolution is subjected to very decided periodic planetary influences, which sometimes destroy the balance of the seasons. The researches of Mr. Meldrum and others appear to corroborate the long-suspected physical connection between terrestrial cyclones and those grand solar atmospheric storms which produce or constitute sun-spots. A recent writer, summing up the latest results obtained from these and many like investigations, concludes that "the solar spots and temperatures
change in parallel cycles, and affect every feature in terrestrial meteorology."
But, apart from every aid furnished by cosmic meteorology to that of our individual planet, the extension of the international simultaneous weather-reports will, we believe, ultimately afford the data requisite for approximately forecasting some main features of the seasons. A single example (the great heat of last October on the eastern side of the United States) will illustrate the possibility of attaining in some degree this long-desired object, which, like an ignis fatuus, has eluded the pursuit of men for so many ages. The summer of 1879 presented in North America no strongly marked high pressure; but after the 24th of July the barometric conditions were generally "low," and in the "Monthly Weather Review" for August, the Signal-Service stated: "The barometric pressure, as compared with the means of the
Chart of Equal Barometric Pressures during August, in and around North America. (Arrows show prevailing winds for August.)
seven preceding years, shows that the mean of the entire country has been abnormally low." We may compare the atmosphere then resting upon the interior to a vast and fixed dry cyclone, the elongated central area of which covered the Upper Lake region, and the country stretching northward, probably to the sixtieth parallel of latitude—the whole extent of the depression not less than 1,500,000 square miles. and the pressure ranging from 29*90 to 29*70 inches. It has long been known that such a "barometric trough," or stationary depression, forms over the northwestern portion of this continent every summer, when the soil is highly heated by the sun, and the air-strata above it become highly rarefied by terrestrial radiation; Mr. Buchan, on his isobaric charts, assigns to it in July a mean pressure of 29*80 to 29*70 inches. Now, by "the law of the winds," the effect of this barometric depression would be to set up an indraught, somewhat resembling that caused by an ordinary cyclone, around whose center, in our hemisphere, the air draws from right to left, and moves on all sides toward the vacuum. Necessarily, therefore, toward the central belt of this vast continental depression (which during last August covered the interior of our continent up to the Arctic Circle), as into an aerial hollow, the air would flow from the surrounding regions of high pressure, which in that month always lie to the southward in the Gulf of Mexico, and in the extratropical parts of the Pacific. Could the Signal-Service barometric observations have been supplemented in August by like simultaneous observations taken in central British America, so as to determine the extent and intensity of the low pressure there, the anomalous autumn of 1879 could have been in no small measure foreseen and forannounced. A "warm wave" was then rolling northward and likely to continue. Could the international system of reports have been extended to the upper valley of the Saskatchewan before this enormous barometric anomaly developed, the prevailing weather of last September and October could have been then measurably foreshadowed, with almost as much certainty as, when a "cold wave" from the north is moving over the Lakes any day in January, the Signal-Office indicates "cold weather" for the interior of the country.
But enough has been said on this part of our subject. The necessity of studying the atmosphere as a unit need not be further pressed; for, as Dove forcibly said, "it is, as its name shows, a great steam-apparatus, whose reservoir is the ocean, its furnace the sun, and whose condensing vessels are the higher geographical latitudes," so that only when viewed as a whole can its operations be clearly understood. The simultaneousness of the present international system insures the accuracy of the results that may be deduced. And the international chart acts as a sort of lens by means of which the scattered rays of meteorological light are concentrated in a focus upon the dark points of the science. It is but just to add that the credit of originating, organizing, and elaborating this simultaneous system, both of the ocean meteorology and that of the land, belongs to General Myer, who, in the execution of his plans, has been seconded by the indefatigable labors of his assistants in the Washington Weather Bureau, and sustained by the energetic cooperation of all foreign weather-services.
The extension of this research can not fail to afford the diligent investigator a magnificent view of the complicate and exquisite adaptations of the atmospheric forces. Humboldt records the circumstance that, when, like Balboa on the summit of the Sierra de Quarequa in Darien, he and his companions from the top of the Andes caught their first view of the Pacific Ocean, so great was their joy, they forgot to open their instruments, and every thought was hushed that they might drink in the scene expanding before them. How much more will the meteorologist of the near future, whose mental eye catches a clear glimpse of the Aerial Ocean, mirrored in the modern chart, be lost in admiration, yet constrained to admit with the ancient seer, "Lo! these are but parts of His ways; how little a portion is heard of Him, but the thunder of His power who can understand?"