Popular Science Monthly/Volume 41/October 1892/A Chapter in Meteorological Discovery
|A CHAPTER IN METEOROLOGICAL DISCOVERY.|
ONE of the most interesting phases in the history of scientific research is what may be called the co-operative feature. No great machine is the invention of one mind. Few great discoveries have been made in complete accuracy by any one man. A locomotive is a mosaic of inventions, discoveries, and improvements. It would be impossible to estimate the number of minds which have contributed to the mighty structure, and have slowly built up its complex perfections. The names of Stephenson, Jervis, Winans, and Allen, in their successive contributions to the devices by which the locomotive has increased its capacities, but faintly hint the immense number who have given some detail, some great or small modification and improvement by which the vast and impressive result has been built up. In the same way, every science grows to its completeness by the accumulating discoveries of individuals, added from year to year and century to century. Astronomy has gathered its harvest of results by the hands of hundreds of patient toilers. Copernicus established the true center of the solar system; Kepler added the three great laws which bear his name, relating to the orbits and the periods of the planets; Newton contributed the law of gravitation. The science has been a growth, fed by the thoughts and the painstaking labors of many minds. And while each of these great men has furnished a distinct and complete contribution to the total knowledge in the science, each has also depended upon his predecessors for co-operation and the data which made his own task possible of accomplishment.
Just such a process as this has been going on in the young and growing science of meteorology. It may be doubted if any other branch of science in our century furnishes a more curious and valuable illustration of the progress of discovery in a given field, the corrections applied by later discoverers to the work of their predecessors, the accumulation of facts and data till they are sufficient for the formation of a working hypothesis, the modifications of the hypothesis in the light of new data, the application of the theory to practical affairs, and the unification of the set of phenomena thus investigated with other and all facts in the same branch of science. The history of the investigations which created our great system of observation and record, and made it possible for a whole people to get daily bulletins of the morrow's probable weather, is one of the most striking in the whole history of science. Let us sketch it as it lies in the annals of the learned societies of America, as yet both uncollected and unconnected. It will be seen how discovery started from a casual hint based on the observations of a keen and well-trained mind; how it was stimulated in a later observer, who bent himself to the painstaking collation of facts bearing on one special set of phenomena; how these facts finally warranted him in advancing a hypothesis; how this hypothesis was opposed and criticised; how it maintained itself in the face of increasing light; how more extended observations confirmed it and enlarged its application; how it became the basis of all subsequent investigation; how it was sustained by the testimony of other observers working along similar lines; and how to-day it is at the very corner-stone of the meteorological science in America. To this narrative let us turn.
It may be fairly presumed that the well-known suggestions of Benjamin Franklin, based on the occurrence of a northeasterly storm in Boston shortly after one was noted in Philadelphia, was the first definite contribution to the scientific knowledge of North American storms and their movements of transition. Though that contribution was little more than a speculation, it was nevertheless one of those sagacious anticipations of results which marks the true scientific genius. In a letter to Jared Eliot, dated at Philadelphia, July 16, 1747, Franklin says: "We have frequently along this North American coast storms from the northeast which blow violently, sometimes for three or four days. Of these I have had a very singular opinion for some years—i. e., that though the course of the wind is from northeast to southwest, yet the course of the storm is from southwest to northeast; that is, the air is in violent commotion in Virginia before it moves in Connecticut, and in Connecticut before it moves at Cape Sable."
In another letter to Eliot, dated at Philadelphia some two years later (February 13, 1749-'50), Franklin says: "You desire to know my thought about northeast storms beginning to leeward. Some years ago there was an eclipse of the moon at nine in the evening which I intended to observe, but before night a storm blew up at northeast and continued violent all night and next day; the sky was thick clouded, dark, and rainy, so that neither moon nor stars could be seen. The storm did a great deal of damage all along shore, for we had accounts of it in all the newspapers, from Boston, Newport, New York, Maryland, and Virginia. But what surprised me was to find in the Boston newspapers an account of an observation of the eclipse made there, for I thought as the storm came on from the northeast it must have begun sooner in Boston than with us, and consequently prevented such observation. I wrote to my brother about it, and he informed me that the eclipse was over there one hour before the storm began. Since which I have made inquiries, from time to time, of travelers and of my correspondents to northeast and southwest, and observed the accounts of newspapers from New England, New York, Maryland, Virginia, and South. Carolina, and I find it to be a constant fact that the northeast storms begin to leeward, and are often more violent there than to windward."
Those letters are probably the earliest literature on the subject of North American storms, the first documents of scientific value in the long series of observations and of studies which have brought us to our present valuable knowledge. Undoubtedly, this fact, which had suggested itself to Franklin, had been observed before by fishermen, by mariners, and others, accustomed to the practical observation of the weather. But this is the initial point of its treatment as a scientific phenomenon. Between the two kinds of observation there is a world-wide difference. The observer is not always nor often the seer. There are a hundred thousand who can note a fact for one who can draw an inference from it. A good many myriads of generations had noted the ebb and flow of the tides before anybody noted a connection between these facts and the daily passage of the moon across the meridian. It is likely that a good many fishermen and sailors and captains had talked over the curious fact that the first signs of the coming northeaster seemed to be from the leeward of its characteristic wind. Perhaps some of these unscientific folk had propounded their crude theories about the motions of storms to the little knots of comrades about the cabin fire or under the forecastle's dim lantern. But, being unscientific people, they did not know how to gather and marshal their facts, draw their inferences, and declare their hypotheses. And so Dr. Franklin must have the credit of first propounding this doctrine about American storms. Many years elapsed before his became the accepted view, and people understood that the easterly storms of New England, and indeed of the whole country, were travelers from west to east, and not visitants from the sea, drifting up the coasts and inland. The lack of facilities for observation, the dearth of data, the infrequency of communication, the almost utter neglect of the phenomena whose study in recent years has founded the science of meteorology, were all conditions which greatly retarded the knowledge of meteorology in our own country, and made it impossible to trace the connection of weather in one region with that in others.
William C. Redfield.—The serious and consecutive study of the motions of North American storms may be said to have begun with the investigations of William C. Redfield, one of the most painstaking, broad-minded, and sagacious of American scientists. So competent an authority as Commodore Maury has called him "the Kepler of storm physics." Prof. Denison Olmstead, of Yale College, in a brief memoir published in the American Journal of Science (vol. lxxiv), says: "The honor of having established on satisfactory evidence the rotary and progressive character of ocean storms, and determining their modes of action and laws, it is due alike to the memory of the departed and the credit of our country to claim for William C. Redfield."
Redfield was a Connecticut man, born at Middletown in 1789. He was a naval engineer, and, besides his valuable contributions to this science, he was much interested in various other branches, and especially in the problem of increasing the speed of steamboats. Olmstead declares him to have been the first man to suggest a great railway system between the Hudson and the Mississippi.
It was in the year 1821 that Redfield began the study of what he called "Atlantic storms." He was led to it by a casual circumstance, like that which called out Franklin's hint as to the direction of the movement of these storms. And let it especially be noted, as the story of his investigation is told, how clearly that story teaches the value of close and patient study along some single line of facts, until their relations are laid bare and their meaning uncovered. Redfield is an illustration of the value to the world of men who know, not a great many things a little, but a few things a great deal.
In the year 1821 a severe storm prevailed along the Eastern coast, which for many years was known as the "great September gale." It held that title until September, 1869, when another and more remarkable one occurred, which rather disturbed its claim to the honor. It was a little time after this first storm that Redfield, while making a journey in Massachusetts, was struck by a somewhat curious fact. He noticed that in Massachusetts the trees prostrated by the wind, all lay with their heads to the southeast, showing that the gale there was from the northwest; but in Connecticut the trees blown down in the same storm lay head to the northwest, showing that the gale had been a southeast one. He ascertained, moreover, that when the wind was blowing southeast in Middletown, his home, it was northwest at a place not seventy miles from there. It was then that the idea flashed across his mind that the gale was a progressive whirlwind. That was a great thought. It was such a flash of perception as came to Newton when he connected the falling apple with the planets in space. It was such an insight into the meaning of a fact as James Watt had when he saw the possibilities of the force that was rattling the lid of the kettle on his mother's fire. The development of that idea was destined one day to put Redfield in the ranks of the great scientific thinkers of his day. He made this storm the basis of his investigations, following his researches into its movements by a careful collection of facts in relation to others like it. For ten years he studied, and examined and compared his facts, before lie published his theory of storms. He noted the occurrence of several great gales, and set about collecting all the facts possible in reference to them, carrying on a wide correspondence, and examining a multitude of witnesses. He sought out the marine reports as to all vessels coming into port soon after the storm, examined their log-books and talked with their captains. In the case of the great Cuban hurricane of 1844, he collated one hundred and sixty-four different accounts. He noted the latitude and longitude of the vessels at sea, or the observers on the coast, when they took the gale, the direction and force of the wind as they experienced it, the direction in which it veered, the states of the barometer, and all cognate facts. Then he charted the whole and studied its meaning.
It was in 1831, ten years from the time in which he first observed the effects of the September gale and drew his inferences from them, that he published an article, "On the Prevailing Storms of the Atlantic Coast." In it he gave an account of the gale of 1821, which he describes as "exhibited in the form of a great whirlwind." He had now made several important conclusions in reference to this class of storms: 1. He held that they often originate in the tropical latitudes, frequently to the north and east of the West India Islands. 2. That they often cover at the same moment of time an area of from one hundred to five hundred miles in diameter, and that they are most violent nearest the center of this area, and least energetic about the exterior lines. 3. That while in the tropics these storms move from east to west till they reach the parallel of 30 north, when they suddenly recurve to the north and east, and move rapidly along lines generally parallel with the Atlantic coast of the United States. 4. That the direction of the winds along the greater portion of its storm-tracks is not the same as the direction of the storm itself. 5. That when in these northerly latitudes these storms, while moving in a northeast course, begin with a wind from east to south, and terminate with a wind from west to north. 6. That on the outer portion of the track, north of the parallel of 30 or within that portion lying farthest from the American coast, these storms exhibit at the commencement a southerly wind which, as the storm comes over, veers gradually to the westward, a quarter where it is found to terminate. 7. In the same latitudes, but along the central portion of the track, the first force of the wind is from the southeast, but after blowing for a certain period it changes suddenly to a point nearly or directly opposite. 8. On that portion of the track nearest the American coast or farthest inland, if the storm reaches the continent, the wind commences from an east or northeast point and veers more or less gradually by north to northwest.
This was certainly a very important series of conclusions, and it establishes certain principles or laws in regard to a certain class of North American storms beyond cavil. Redfield had thus shown that many at least of the great storms which traverse the Atlantic coast come from the tropics east of the West Indies and describe a great parabola in their course; that the direction of the wind in these storms was entirely a distinct matter from the direction in which the storm is moving; and that this storm is a system of winds, blowing whirlwind-fashion about a central point, in a direction contrary to that of the hands of a watch. That is the substance of Redfield's discovery; and it is one of the most important contributions ever made to the science of storms, not alone in its purely scientific relations, but also, as we shall see, in a most practical way in the service of mariners.
Just here we touch an interesting episode of Redfield's career, in his connection with Sir William Reid, an English engineer-colonel at Barbadoes, himself deeply interested in this subject, and an investigator of the law of storms in general. Redfield and Reid entered into a correspondence upon the subject which lasted for twenty years, and which Redfield declares was most serviceable to him. But, as Colonel Reid's earliest inquiries were based on a storm of 1831, ten years later than the one which gave Redfield his first hint of a theory, it may still be maintained that Redfield was the first to grasp the new facts in all their meaning. He acknowledges an indebtedness to Colonel Reid as well as to Piddington, in his essay on "Asiatic Storms." But their work could have done little more for him than to confirm his own thought and guide his investigations. It remained for this early student of these phenomena to follow the great storms of the Atlantic from their breeding-place near the "doldrums," in their curving path through the Gulf of Mexico and along the United States coast, proving that these vast hurricanes of the West Indies are progressive storms, moving westward till central in the Gulf and then recurving toward the northeast, retaining their essential characteristics, though somewhat less violent than in their beginnings. This was the scope of Redfield's investigations. He indicated the track of one entire class of American storms, and showed them to be great circular movements of the air, like immense whirlwinds or cyclones, traveling bodily over wide areas.
A word more ought to be said before we pass from the work of Redfield, as to his theory of the direction of the winds about the center of a cyclone, a point much debated since his day, and in which he was singularly correct in his judgment. At the time he made his investigations, everybody supposed that these great storms were disturbances in which the winds blew straight away from one point of the compass; and one of the theories advanced in opposition to this, held that the winds in these systems blew radially in to a common center. Redfield, however, maintained that they blew neither radially toward the center, nor yet in circles around it, but as water or smoke in a vortex, with a constant inclination to the center. Here, too, he came very close to the most commonly received doctrine of this present time; and it proved in entire harmony with the law propounded by Ballot—a law which may be thus expressed: "The wind which blows around an area of low barometer, blows neither in circles returning on themselves, nor directly toward that point; but it takes a direction intermediate, approaching, however, more nearly the direction of circular curves than of radii to a center." Redfield's researches also showed that the winds about a low-pressure space blow in a direction contrary to that of the hands of a watch.
One fact more should be stated in reference to the nature of Redfield's work and its practical value. Few discoveries in science have ever been turned more quickly to the benefit of mankind; for one of Redfield's first undertakings, after establishing these laws of the great Atlantic storms, was to formulate certain rules for the management of vessels during these gales, by which the heaviest force of the storm may be avoided. One of the completest answers to the skeptical queries of matterof-fact people as to the utility of purely scientific studies, is found in the fact that the outcome of Redfield's studies as attested by United States naval officers like Commodore Rodgers and Lieutenant Maury, was an immediate service to ship-masters in showing them how to avoid the heaviest parts of a cyclone, and save their vessels the risk and the wear and tear of an encounter with the violent winds of the storm-center.
James P. Espy.—But we must leave the work of Redfield, important though it was, and move on, in fulfillment of our purpose, to note the contributions of those other men who helped to complete our knowledge of great American storms.
In the year 1850, Prof. James P. Espy, one of the most original and talented of American meteorologists, published his conclusions in regard to the character of American storms, which must be regarded as the next step in the enlargement of our knowledge on the subject. His views were presented in a work entitled The Philosophy of Storms, the fruit of earnest and painstaking studies. The great feature of this work was its presentation of a new class of storms. Espy directed attention to those great atmospheric disturbances which no one hitherto had dealt with, which move across the continent from west to east and which do not originate in the West Indies. Redfield's attention, was confined to his favorite West Indian storms, which travel via the Gulf of Mexico. Espy reminded the public that these were not the only great storms which visit the United States.
"There are rain and snow storms," said Espy, "which from November to March, at least, travel from west to east. These storms are first heard of west of the Mississippi and sometimes as far north as Iowa; and they often travel from the Mississippi to the Connecticut in twenty-four hours." He concluded that these storms must originate in the far West, at that time only a wilderness, and so beyond the outposts of observation. Espy did not assert that these storms differed in character from the ones with which Redfield had dealt. He only reminded the world that the West Indies were not the only place where storms were generated. In so doing, he accurately pointed out the origin of a large proportion of American storms. The storms which Bedfield studied were really the least, in point of numbers, among the storms which visit the continent. But Redfield's observations were confined to the seaboard, so that he necessarily did not have his attention drawn to this second class of great storms. Like many later Eastern men, he did not realize what a prominent part the West plays in the economy of the country.
In two respects Prof. Espy became the critic of William C. Redfield. He held that the winds related to great storms blow radially to a center, either obliquely or directly. He also believed that the depression of the storm-center was caused, not by the centrifugal force generated by the motion of the winds, as Redfield was inclined to maintain, but was on account of the rarefaction of the air through the heat developed by the condensation of vapor in the form of rain or cloud. The latter theory proved of more value than the former, and will stand as one of Prof. Espy's additions to the meteorology of North America. The Western origin of many storms and the function of heat in the development of cyclones—these are the two contributions of Espy to the science of American storms.
Prof. Hare.—But Espy's eyes were not sharp enough to see all the facts about the origin and movement of our great disturbances; and so, as he made certain suggestions which added to the value of Redfield's discoveries, his own in turn received amendment. The chief of Espy's critics was that eminent American scientist, Dr. Hare, whose queries in regard to Espy's conclusions were pertinent and searching. He asked, among other things, "whether agreeably to the observations of Franklin and general experience confirming them, our storms producing northeasterly winds do not travel from southwest to northeast; whether their traveling thus does not warrant the opinion that they originate in the Gulf of Mexico: whether the observations of Redfield do not establish the fact that certain storms travel from the Gulf along the coast; how the observations of Franklin, confirmed by the general impression that they were sagacious, can be reconciled with those made by Loomis (locating the place of origin of some storms in the Northwest of the United States), unless there be two kinds of storms, one of which travels from southwest to northeast and the other from northwest to southeast; and whether it can be correct to confound these two kinds of storms under one generalization—i. e., storms moving from east to west." Of course, these slight strictures did not seriously affect the validity of Espy's conclusions, any more than they added materially to the sum of Redfield's. They simply helped to bring all the facts now discovered into relation, and take the emphasis off any especial class, the peculiar study of individuals. They show how valuable are all individual contributions to the growth of a science, and how, when there is a number of observers in any one field, each may be a check upon the others and supplement their defective data or inferences. Redfield discovered the origin of one class of storms, and laid down the laws of their movement and internal motions. Espy pointed out a new point of origin of storms, and threw some new light on their internal winds. Hare pointed to still another quarter whence these great whirlwinds arise, and directed attention to the various tracks which they pursue; and the investigations which led to these results extend over a term of perhaps thirty years, from the year 1821 to 1851.
Elias Loomis.—It was about this period that Prof. Loomis, of Yale College, was prosecuting his studies in meteorology, and especially in regard to storm-motions, which have since become a valuable part of our knowledge. He was a later worker in this field, and his labors were made the more valuable from the fact that the country had been growing rapidly, especially toward the Northwest, and he was thus enabled to command much new material in the way of observations from this quarter of the country, which had not been available for the others. Loomis found that great storms, of like character to those reported from the southwest and the Atlantic coast, also swept the northern parts of the country, with identical details, in respect to winds and motions. These were included in his studies, and thus the generalizations in respect to our storms were greatly enlarged. Perhaps the gist of Loomis's conclusions in this matter is condensed into this paragraph from his Meteorology, which, by the way, was the first treatise of any pretensions upon this subject published in this country. He says: "The average direction of storm-paths across the United States is toward a point nine degrees north of east, but it varies somewhat with the season of the year, being almost exactly east in summer and inclining more to the north in the winter. Occasionally storms depart very much from the average track, their course being sometimes directed toward the southeast and sometimes toward the northeast, and occasionally their course for a day or so has been almost exactly north. Their average velocity of progress is twenty-six miles per hour, being twenty-one miles in summer and thirty miles in winter; but sometimes they attain a velocity of fifty miles in an hour, and sometimes they remain for a day or two sensibly stationary."
Blodgett, Mitchell, Coffin.—Several other names deserve mention, as belonging to earnest investigators and theorists in the early fields of American meteorology. Loren Blodgett, M. N. I., published in 1857 a work on the climate of the United States, far superior to anything previously sent out. About the time of Redfield's earlier work, Prof. Mitchell, of the University of North Carolina, propounded a theory which seems to have attracted but little attention—as indeed it deserves but little—maintaining that certain storms, especially those of the Atlantic coast, are the result of a gyratory motion about an axis parallel to the plane of the horizon. This proposition he held in opposition to Redfield, whom he mentions as contending for the revolution of the wind about an axis perpendicular to the plane of the horizon. This speculation of Prof. Mitchell was of less value to science than his suggestion of the plan of daily maps, showing the aspects of the sky, that cloud boundaries might be traced, and thus their extent and movements discovered an idea which is incorporated into the every-day work of the Signal Service at Washington. Still another of the meteorologists of service in the line of investigation we are describing was Coffin, the author of Studies in the Winds of the Northern Hemisphere.
Dr. Joseph Henry.—When the study of the laws of storms and their movements in America had gone as far as this, it had reached a point beyond which it could not proceed without a more abundant material in the way of observations and statistics. More data were required, if larger demonstrations were to be made. The time had come when no great advance in the knowledge of storms could be had, unless they were carefully studied over large areas, their actions noted at a great number of points at once, and the information thus gained reduced to order. Of no other science is this so true as of meteorology; of no branch of meteorology is it so true as the observation of storms. Eternal vigilance is the price of all knowledge in this great field. And we are now at a point in the progress of the study of American storms when a great advance was made. Prof. Joseph Henry, the Director and Secretary of the Smithsonian Institution, and one of the very foremost of American physicists, put into execution a plan long conceived and long agitated, securing a system of daily observations throughout the United States and Canada. He first arranged for daily reports by telegraph, and was the first to have the atmospheric conditions over a large territory indicated on a map. He paved the way for the systematic researches of that department of the public service which has since been organized as the Weather Bureau, established in 1870, the most important work in the interests of this science which has ever been undertaken. For it is now possible to put in the hands of a few trained minds at Washington, three times in every day, an amount of data many times more than all that Redfield or Espy or Hare collected in years of study. It is to the efforts of Dr. Henry, following upon the patient research of the men whose work we have thus slightly traced, that we owe the rise and growth of the science as it stands to-day. An army of observers, drilled to the greatest precision of scrutiny, on land and on sea, on hill-tops and in the valleys, in every latitude from the equator to the polar circle, scans the heavens and watches the earth for every meteorological change. The charting of great storms, the making of forecasts, the posting of storm-warnings, all indicate the condition which this science has slowly attained, through the combined and cumulative labors of so many patient observers. From the conjecture of Benjamin Franklin, about the northeast storms beginning to leeward, to the splendid system by which the movements of a great storm are announced and described almost as regularly and clearly as the movements of trains on a railway system is a long advance. It is an advance which shows how much we have to be proud of in this great national work, as it has grown and developed at the hands of our own countrymen. It illustrates, moreover, the fact that in the researches of science, as in all the labors of humanity, every man's work tells, and enters into the great result. Patient toil concentrated upon chosen subjects never fails to yield its due results, valuable for all men. Even the most abstruse scientific research may have, nay, will surely have, its issue in practical good to men; and the most retiring and isolated student in his solitary studies is as true a servant of his kind as he who sows and reaps acres of wheat, or weaves the cloth that clothes men's bodies. When William C. Redfield was gathering the facts about his Three Great Atlantic Storms, he was doing as direct a service to the future shippers and navigators of the Atlantic coast, and the cotton-growers of Georgia and Alabama, as if he had furnished cargoes for their ships or markets for their cargoes.