# Popular Science Monthly/Volume 37/September 1890/Sketch of Thomas Corwin Mendenhall

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THOMAS CORWIN MENDENHALL.
* SKETCH OF THOMAS CORWIN MENDENHALL.
By GEORGE ILES.
AMERICA is rich in men who have proved how much more decisive in a career of usefulness is nature than nurture, the instinct for acquiring knowledge than facilities for instruction, a worthy ambition to render service to one's fellows than all the means and agencies which wait upon circumstances ordinarily and often ignorantly called favorable. Such a man is the subject of this sketch.
Thomas Corwin Mendenhall was born on October 4, 1841, near Hanoverton, Ohio. On his father's side he is of Quaker stock, tracing his descent from Benjamin Mendenhall, who emigrated from Wiltshire, England, with William Penn, and settled in Delaware County, Pennsylvania. Young Mendenhall's schooling was of the scanty kind afforded by small country villages more than a generation ago; defective though it was, it developed in him at an early age a fondness for the study of mathematics and the natural sciences. He gradually won for himself an education which his opportunities would have denied to a less sturdy spirit.
Among the most important influences working for his mental development in boyhood was the encouragement of his father, who, while he had enjoyed only limited opportunities for educational training, was an earnest, thoughtful man, and fond of reading. From him, along with the conviction that there must be an antecedent cause for every effect, he derived a disposition to investigate causes and inquire after reasons. Another impulse, which must have had a very considerable effect upon the determination of his future career, was given him by one of his teachers in the old log school-house—a good Quaker lady, who had a way of setting her pupils to making simple experiments, and thus, as he has said to us, directed the first physical laboratory that he ever entered. She taught him that a ray of light was bent in passing from one medium to another of different density, by means of the-old and familiar experiment with the coin and tin cup. On another occasion, by darkening the windows, except for a small opening in the ​corner of one of them, with the shawls of the girls, she showed how an image of the big boys jumping from a "spring-board" outside was projected on the roughly plastered ceiling. Such experiments and illustrations made a great impression on him, as they undoubtedly did on his fellow-students, and, we may assume, produced lasting influences that varied in each according to the bent of his mind. Young Mendenhall read also with great eagerness the small volume of Comstock's Natural Philosophy which fell into his hands about this time, and was allowed to draw the cuts of levers, pulleys, etc., on the blackboard at school. He experimented on the law of the lever when, with the other boy who had been detailed with him for the duty, bringing water from a distant spring to the school-house, the pail was carried between the two on a stick. He had a taste for mechanical operations and was something of an inventor, and was especially fond of mathematical studies. Of the few books in the small family library Chambers's Information for the People was his favorite, and he read and reread it till he nearly knew it by heart. In astronomy he made his first observation by means of a semicircle of wood which he had roughly graduated and mounted in the meridian, and on which the line of collimation was determined by two pins at the extremities of the diameter. When about eleven years old he made an unsuccessful trial of Foucault's experiment to prove the rotation of the earth, of which he had read in a newspaper. When it became necessary for him, at an early age, to care for himself, he continued his studies at odd times as he found opportunity, still attending school as regularly as he could. Rainy days on the farm were eagerly made use of for reading and study. Studies in algebra were carried on while he was employed in a saw-mill, and the problems were worked out on loose boards with chalk. "More than to all other sources, however," Prof. Mendenhall remarked, "I am indebted to the friendly advice, encouragement, and assistance of teachers and others with whom I came in contact. To be made to think that I could do something or had done something by a word of kindness or congratulation was to be helped along immensely."
Remembering the waste of time, the discouraging, because useless, difficulties of his youthful struggle, Prof. Mendenhall has ever been a faithful advocate of bringing the highest education and the best scientific culture within the reach of every seeker of it. His proficiency in science soon developed itself in the perfect form needful to one who would successfully teach. In 1873, on the organization of the Ohio State University, he was elected to the chair of Physics and Mechanics, which he held until 1878, when he accepted the professorship of Physics in the Imperial University of Japan at Tokio. While in Japan he organized a ​special course in physics, and established a physical laboratory in connection with the science department of the university. In addition he founded a meteorological observatory, which after his departure was merged into the general meteorological system established by the Japanese Government. Prof. Mendenhall furthermore carried out an investigation on the force of gravity at the sea-level and on the famous Japanese extinct volcano Fujinoyama. His measurements of the figure of the mountain and of its density enabled him to deduce a value for the mass of the earth which agrees very closely with that of Francis Baily as obtained by the Cavendish method. About this time he also made a series of elaborate measurements of the wave-lengths of the principal Fraunhofer lines of the solar spectrum by means of a large spectrometer, then one of the best in existence. This work was done before Prof. Plenry A. Rowland had produced his famous diffraction gratings, but some fine specimens of Lewis M. Rutherfurd's rulings were used. No precise measurements of these rulings were undertaken; hence Prof. Mendenhall's results were only valuable as ascertaining the relative spaces of the various portions of the spectrum; as such they rank among the best given to the world previous to the recent researches with gratings of accurately known and more minute division.
Japan is a land of frequent earthquakes, and Prof. Mendenhall soon became interested in studying their phenomena. That this study on his part and that of others might be systematic and cooperative, he aided in founding the Seismological Society of Tokio. While ardent in his university work and an unsparing toiler in diverse fields of original investigation, Prof. Mendenhall felt that he had a duty to men and women who could not enter his classes nor read the scientific memoirs he was writing. With Prof. Edward S. Morse, then in Japan, and others, he gave lectures on scientific themes to popular audiences in the temples and theatres of Tokio. So thoroughly was an intelligent curiosity thus aroused in the city, that soon a public lecture hall was estab* lished—the first in the Japanese Empire.
In 1881 Prof. Mendenhall returned to the United States and resumed his chair at the Ohio State University. In the following year he organized the Ohio State Weather Service, of which he was director until 1884. While holding this office he devised and put into operation a system of weather-signals for display upon railway trains. This system was generally adopted throughout the United States and Canada; in 1887 it was superseded by a new code introduced by the Chief Signal Officer. In the United States Signal Service at Washington Prof. Mendenhall received an appointment in 1884. Here he organized and equipped a physical laboratory in connection with the office of the Chief Signal Officer, ​and inaugurated systematic observations of atmospheric electricity. One of the results of his work was proof that rain precipitation is the cause rather than the-effect of electrical discharges in the atmosphere. He concurrently investigated the methods for ascertaining ground temperatures, inventing improved forms of apparatus. Pursuing a line of inquiry begun in Japan, he established the systematic gathering of data regarding earthquakes from stations scattered throughout the United States. Immediately after the earthquake of August 31, 1886, he visited Charleston, and made a report upon the agitation with a co-seismic chart showing the disturbed area. It seems probable that, before many years elapse, the phenomena of earthquakes will have sufficiently yielded their secrets to enable predictions of their occurrence to be made, following up and perfecting the methods by which the Weather Bureau now issues its forecasts. In this branch of science, as important as it is difficult, Prof. Mendenhall has done invaluable work as a pioneer. After two years' service of the Government, he resigned, to accept the presidency of the Rose Polytechnic Institute in Terre Haute, Indiana. His new responsibilities were discharged with marked success; he brought to them rare address, tact, and executive ability. The Institute, young as it was, soon had an assured place among the leading technical schools of the country. That it supplies an educational need in the flourishing city in which generosity has placed it came out plainly at its commencement exercises last year. On that occasion Prof. Mendenhall was able to say that every member of the graduating class had secured an engagement and was fairly launched upon his life-work.
In July, 1880, Prof. Mendenhall was nominated by the President to fill the superintendency of the United States Coast and Geodetic Survey, one of the most important scientific appointments in the country, and which has been held by men of the stamp of Alexander Dallas Bache, Benjamin Peirce, and Julius E. Hilgard. Prof. Mendenhall succeeds to their fame, but also to administrative duties which have grown more onerous with every year of the survey's history. He has nevertheless an opportunity for scientific work which his energetic and organizing mind is not likely to leave unimproved. His interest in the gravitation work which the survey has carried on for several years has led to the formation of new plans for its more rapid and vigorous prosecution. For some time past the survey has been engaged in the study of terrestrial magnetism; its researches in this direction are being actively pressed forward, one aim being to locate the north magnetic pole with precision. In geodesy the survey is steadily advancing the great transcontinental system of triangulation, and some new contributions of importance toward our knowledge of ​the earth's figure are likely to be presented at an early day. As Superintendent of Weights and Measures, Prof. Mendenhall enters upon another field of duty for which his work in the past has been a preparation. He has long borne a prominent part among the teachers who have pressed and still continue to press the metric system upon the American public. He is an active member of the American Metrological Society, and has repeatedly, on the platform and through the press, taken occasion to impeach the current irrational medley of pounds avoirdupois and troy; of grains, gallons, feet, and bushels.
Prof. Mendenhall has uncommon gifts as a lecturer; his masterly expositions of physical themes continue to be given despite the pressure of official duties. At the Cooper Institute in New York, the Lowell Institute in Boston, the Peabody Institute in Baltimore, the Mechanics' Institute in Cincinnati, the Brooklyn Institute, and in other of the chief popular lyceums of the country, he has been greeted by large audiences. The honorary degree of Ph. D. was conferred on him by the Ohio State University in 1878, and that of LL. D. by the University of Michigan in 1887. In the latter year he was chosen a member of the National Academy of Sciences. He was elected a member of the American Association for the Advancement of Science at the Indianapolis meeting in 1871, and was advanced to the grade of Fellow in 1874. In 1882, at the Montreal meeting, he presided over the Section of Physics. His address on that occasion was a forcible plea for physics in education, presenting a judicious view of the value of guidance when students attempt original research. In 1888 he was chosen President of the Association, and in that capacity at last year's meeting, in Toronto, won golden opinions on all hands. At the approaching meeting in Indianapolis he will, it is understood, take for the theme of his address, as retiring president, The Relation of Science and Scientific Men to the General Public.
In 1887 he contributed the first volume to The Riverside Science Series, A Century of Electricity. A revised and enlarged edition of this capital popular treatise has been issued this year. From among his numerous contributions to scientific publications we select: On the time required to communicate impressions to the sensorium and the reverse, American Journal of Science, 1871; On the heaping of liquids, American Journal of Science, 1873; An improvement on Bunsen's method for specific gravity of gases, Proceedings of the American Association for the Advancement of Science, 1878; Temperature and index of refraction, American Journal of Science, 1876; Co-efficient of expansion of a diffraction grating, American Journal of Science, 1881; Memoirs of the. Scientific Department of the University of Tokio, ​Japan: (1) Report on the meteorology of Tokio, 1879; (2) Report on the meteorology of Tokio, 1880; (3) Measurement of the force of gravity at Tokio and the summit of Fujinoyama, 1881; (4) Wave-length of some of the principal lines of the solar spectrum, 1881; The influence of time on the change in resistance of carbon under pressure, American Journal of Science, 1882; Differential resistance thermometer, American Journal of Science, 1885; Report on the Flood Rock explosion, Science, October 1885; On the electrical resistance of soft carbon under pressure, American Journal of Science, 1886; On characteristic curves of composition, read at the American Association for the Advancement of Science meeting, 1886, published in Science, March 1887; Seismoscopes and seismological investigations, read at the meeting of the National Academy of Sciences, 1887, published in American Journal of Science, 1888; On an improved form of quadrant electrometer, read at the meeting of the National Academy of Sciences, 1888; On the intensity of earthquakes, with approximate calculations of the energy involved, Proceedings of the American Association for the Advancement of Science, 1888; On globular lightning, American Meteorological Journal, 1890. A memoir of researches in atmospheric electricity, read before the National Academy of Sciences in 1888, is now in course of publication.