Popular Science Monthly/Volume 46/November 1894/Sketch of Sears Cook Walker
|SKETCH OF SEARS COOK WALKER.|
A FEW years before the middle of the present century the condition of science in America was far from inspiring. Although this country had long since ceased to be a dependency of Great Britain politically, it still seemed unable to rise out of such a position intellectually. In science and letters English authority was paramount. To the generality of American scholars a grudging mention in an English publication outweighed domestic honors of a much higher grade. Scientific treatises emanating from Great Britain were accepted as gospel, while the science of the rest of Europe was known only through British translations. There were a few men of science who were independent in the midst of dependency. The above description shows the general character of a period happily long since brought to an end, and among those most active in bringing about its end was the subject of the present article.
Sears Cook Walker was born March 28, 1805, in Wilmington, a small town of Massachusetts, about sixteen miles northwest of Boston, where four generations of his ancestors had lived and died. His father's mother was descended in a direct line from the celebrated Elder Brewster, who came over in the Mayflower. Sears was a delicate child and so precocious intellectually that he early became the wonder of the village. His father had died when he was a mere infant, so that his whole care and training devolved upon his mother. She fortunately realized the importance of providing for his physical welfare and checking his too great fondness for books. It was a constant struggle with the boy's natural inclinations to do this, but the effort was successful. He joined heartily in many of the sports of his companions, and gradually gained a good measure of health and strength.
Young Walker took the studies preparatory for college at the academies of Andover, Tyngsborough, and Billerica; then went to Harvard, where he was graduated in the class of 1825. Immediately after his graduation he took up teaching as an occupation and followed it for ten years—the first two years in the vicinity of Boston and the rest of the time in Philadelphia. From 1836 to 1845 he was actuary of the Pennsylvania Company for the Insurance of Lives and Granting Annuities. His life in Philadelphia was a period of prosperity and comfort; he, moreover, early took on a corpulent habit of body, so that whatever influence his circumstances exerted was adverse to any strenuous intellectual exertions, and to the obtaining of adequate physical exercise. Yet his mind was one that could not be idle. "While engaged with his school," says Benjamin A. Gould, in his memorial address, "he studied medicine, and went through the whole course requisite for the attainment of a degree. He devoted his leisure for a period to the study of natural history, and was no mean proficient in geology and mineralogy, as well as in physics and chemistry. He was an active member of the Pennsylvania Geological Society, of the Committee of the Franklin Institute on Science and Art, and one of the most useful members of the American Philosophical Society. By frequent articles upon scientific topics in the various prints, by elaborate reports upon various subjects to the Franklin Institute, and by monthly announcements in its Journal of occultations and other celestial phenomena, he kept awake the interest and sympathy of the community for studies of this character. Among other labors, he prepared, in 1834, an ingenious set of parallactic tables, by which the time required for computing the phases of an occultation was reduced to less than half an hour. These were calculated for the latitude of Philadelphia, and it was his intention to publish them in a more general form adapted to different latitudes. But, as this would have been a work requiring considerable time, he subsequently abandoned the project, believing that he could employ his leisure hours more usefully. He continued the computation of the occultations without interruption for six years, and then induced our well-known colleague, Mr. Downes, to undertake the continuance of the work. It has been prosecuted to the present time, with what success we all know, and has of late years been published by the Smithsonian Institution and the Astronomical Ephemeris. Astronomy and geography in America are much indebted to Mr. Walker for these labors, since many already in possession of the necessary means were stimulated by the periodical announcements, and by his personal exertions in still other ways, direct and indirect, to observe these phenomena. An extensive series of such observations was collected by Mr. Walker and published in the Proceedings of the American Philosophical Society."
During most of Walker's residence in Philadelphia he must be regarded as an amateur rather than a scientist. For many years his interest in Nature was spread over several fields, but gradually it concentrated upon astronomy. He had procured an astronomical clock, a twenty-inch transit instrument, and a small Dollond telescope, and from about the time when he gave up his school to become actuary of the insurance company all his leisure was devoted to astronomical observation and study. "In 1837," Dr. Gould's account continues, "he was invited to propose a plan for an observatory in connection with the Philadelphia High School, an invitation which he accepted with eagerness. In accordance with his suggestion, the committee in charge of the school imported from Munich the excellent Fraunhofer equatorial and Ertel meridian circle which, in his hands and those of his accomplished brother, the present director of the observatory, have done so much for astronomy in America not merely by the number of observations made with them, but also by the incentive which they afforded to the lovers of astronomy in other parts of the country. It is unquestionable that in several instances they induced successful efforts for the procurement of similar and even superior apparatus elsewhere." The results of Walker's researches appeared from time to time in the publications of the American Philosophical Society and various journals. It was in 1841 that he may be said to have "earned his spurs" by a paper on the periodical meteors of August and November, which for many years remained the most important memoir on the subject that had appeared. From that time on he is to be ranked among scientific investigators.
In 1845 Mr. Walker's affairs underwent a revolution. Certain commercial operations turned out disastrously and entirely bereft him of means. The sense of defeat, the loss of luxuries at a time of life when habits have become fixed, together with anxiety for the future, made the blow a hard one. But it revealed to him, and to the world, the extent of his own scientific ability, and opened the way to higher intellectual gratifications, which he quickly learned to appreciate. The Secretary of the Navy offered him a position in the observatory at Washington which he at once accepted. Here, for the first time, the facilities which his special gifts required were at his disposal, and he immediately proceeded to make good use of them. After a short time he gave up his position at the observatory to accept the direction of the longitude department of the Coast Survey an office which he ably filled until his last illness.
Early in 1847, while engaged in researches upon the then newly discovered planet Neptune, he became convinced that a star observed by Lalande in May, 1795, must have been this planet. With the telescope of the Naval Observatory Prof. Hubbard confirmed this conjecture, and astronomers were thus furnished with an observation of Neptune made fifty-two years before, which afforded means for a most accurate determination of the planet's orbit. The American was none too soon to secure priority, for, quite independently, the same important fact was laboriously hunted down in Europe by Petersen only a few weeks later. Walker now attacked the problem of Neptune's orbit; Benjamin Peirce was at the same time calculating the planet's perturbations. The approximate results of each furthered the computations of the other, so that within eighteen months from the discovery of the planet these two Americans had attained a remarkably accurate statement of its theory.
In conjunction with Prof. A. D. Bache, Superintendent of the Coast Survey, Walker developed the method of determining differences of longitude by telegraph. "What was the separate share of each of these two men in this work will probably never be known, for each ascribed the chief merit to the other. One feature introduced by Walker was the application of the method of coincidence of beats to the comparison of timekeepers one indicating mean, the other sidereal time at the two ends of a telegraphic line. These beats were signalized from one station to the other by taps of an observer upon the telegraph key. Such signals are, of course, subject to the errors that always attend the action of human nerves and muscles, so the next problem was to make the clock give its own signals. Two methods had been proposed, but there were fears groundless they have since been proved that either of these would injuriously affect the running of the clock. Mr. Walker sought diligently for some apparatus that would not arouse any such fears. He propounded the problem to several astronomers, and two or three contrivances were devised for the purpose.
This mode of observation and the apparatus invented to meet its requirements proved valuable not alone for determinations of longitude, but also for all other astronomical observations requiring minute precision in the determination of time. The mental effort required of the observer being reduced to a minimum, many more transits could be observed at a single meridian passage. Walker immediately modified the transit instrument to suit the new requirements, and, instead of five, seven, or at most nine threads, he provided it with several tallies of five threads each. There remained but one requisite to complete the American method of observation. This was some mechanical contrivance for securing a uniform rotary motion of the record sheet. It had not been attained when Walker died, although some progress toward the solution of the problem had been made.
It is proper for the biographer to point out the share which Walker personally had in this series of inventions, although he was far from making any such claims for himself. With a fine comradeship he was jealous only for the credit of the organization of which he was a member the United States Coast Survey. Speaking to the American Association for the Advancement of Science, Walker said: "With the single exception of the experiment between Baltimore and Washington, in 1844, I know of no telegraphic operation for longitude, and of no step in the improvement or perfectionment of the art, in Europe or America, which has not been the work of the officers proper of the Coast Survey, or of commissioned officers and civilians acting temporarily as assistants. . . . I will not here allude to the respective claims of Americans for priority or superior excellence of inventions and suggestions, believing that it will be becoming for all of us to look to the great work that has been accomplished by our united efforts, rather than to the single share of each."
The transmission of observations by telegraph between Cambridge, New York, Philadelphia, and Washington furnished Walker an opportunity for another important discovery. He found that an appreciable time was required for the passage of these signals, and that this time was less than one tenth of that required for the passage of light over an equal distance in space. This result was so greatly at variance with the ideas of electricity current at the time that it was not accepted in America until the celebrated velocity experiments between St. Louis and Washington put it beyond question, and even after that some European physicists still refused to be convinced. While the matter was in dispute Walker was generous with aid and encouragement to those who sought to test his discovery, whether their results seemed likely to conflict with or to confirm his own.
The English Nautical Almanac for 1856 (issued in 1853) contained a profound discussion, by the astronomer Adams, of the amount of the lunar parallax. In this paper Adams showed that the tables of Burckhardt, which had been the standard ones, contained errors sometimes amounting to 6", and pointed out the effect that such errors must have upon determinations of longitude from occultations. In the greater part of this discovery Walker had anticipated the renowned Adams by more than four years. In April, 1848, he had presented to his chief in the Coast Survey a report on longitudes in the course of which he pointed out the chief errors of Burckhardt's tables, giving four out of the five principal terms with remarkable precision.
Mr. Walker's intellectual labor was intense and unremitting; it was scarcely interrupted even in summer, when he was accustomed to betake himself to Cambridge, to escape the heat of Washington. During one of these summer sojourns, in August, 1851, he suffered a slight attack of paralysis, which for a few days deprived him of the use of one hand. This warning and the entreaties of his friends were not enough to induce him to relax his exertions. In the following autumn he took charge of the expedition for determining telegraphically the differences of longitude between Halifax, Bangor, and Cambridge. Immediately after his return to Washington, at about the end of December, symptoms of mental alienation appeared, and he was taken to the hospital at Mount Hope, near Baltimore. Thence he was removed in the following April to Trenton, N. J., where under the skillful care of Dr. Buttolph, the superintendent of the institution, his disordered brain gradually regained its normal tone. Visits of friends, correspondence on the subjects of his researches, and finally his books and papers were allowed him. While still at Trenton he computed the ephemeris of Neptune for the American Astronomical Ephemeris of 1855. In the fall of 1852 Mr. Walker left the asylum apparently cured, although much debilitated by his illness, and went to Cincinnati for a visit to his brother, Hon. Timothy Walker, intending to remain until the following spring. He took in hand certain labors for the Coast Survey and prepared to resume in full his former sphere of activity. He had fixed a time for returning to Washington and re-engaged his apartments in the city, but he was not destined to make the journey. An attack of fever was followed by other maladies, and Walker soon found himself engaged in a second severe struggle with disease. In this condition Hamlet's problem" To be, or not to be "forced itself upon his thought with all its puzzling considerations. The sound mind in a sound body can give but one reply to this problem, but coming as it did to Walker at a moment when Reason was not firm in her seat, it elicited the opposite response, and on January 30, 1853, he launched himself into the mysterious after-life. His remains were placed in Spring Grove Cemetery, near Cincinnati.
The character of Sears Walker was marked by a childlike simplicity which many persons could hardly realize was not assumed to cover shrewd designs. He was impulsive, but his impulses were always noble and generous. Highly magnanimous, he was always prompt to acknowledge an error, and to overlook not only mistakes but even lapses from honor and justice in others. Intelectually he had the ability of genius. He was unadapted and disinclined for participation in the world's affairs, and could not refrain sufficiently for his physical welfare from intellectual labor.
Although his fame was won in the abstruse field of mathematics, his linguistic attainments were of a high order. In college he was as conspicuous for his classical as for his mathematical ability. During his years of teaching his knowledge of the languages was in daily use, and throughout life the literatures of Greece, of Rome, and of Italy were a source of enjoyment to him. His powerfully retentive memory was stored with long passages from the poets of the past, Tasso being his especial favorite.
- An Address in Commemoration of Sears Cook Walker, delivered before the American Association for the Advancement of Science, at its meeting in Washington, April 29, 1854. From this address many facts concerning Walker's life and work in addition to the above quotation have been drawn.