THE

AMERICAN JOURNAL OF SCIENCE

[FIFTH SERIES.]

HENRY ANDREWS BUMSTEAD.

Henry Andrews Bumstead was born in Pekin, Illinois, on March 12th, 1870. His father was Samuel Josiah Bumstead, a physician of local prominence, and his mother, Sarah Ellen Seiwell. His early education was obtained at the Decatur, Illinois, High School, from which he went to Johns Hopkins in 1887, expecting to study medicine. There he came under the influence of Rowland, who stimulated the interest in physics which he had already shown. After receiving his B.A. degree in 1891, he remained in Baltimore for two years as an assistant in the physics laboratory. In 1893 he was brought to Yale as an instructor by Professor Hastings. He continued his study of physics in the Yale graduate school, and obtained his doctor's degree in 1897. In 1900 he was promoted to an assistant professorship, and six years later he became Professor of Physics in Yale College and Director of the Sloane Laboratory. The year before receiving his doctor's degree he married Luetta Ullrich, of Decatur, Illinois, who survives him.

Professor Bumstead's thesis for the doctor's degree, which does not seem to have been published, contains a critical survey of electrodynamic theories in vogue at the time at which it was written. He states in the introduction that his object is "to set forth the true position of the experiments of Hertz in the history of the development of our knowledge of electricity; and to trace, in some measure, the influence of Helmholtz in the establishment of the true theory of electrodynamics,—an influence which was second only to that of Maxwell." After an analysis of Ampère's and Grassmann's theories, he makes a critical comparison of the potential theories developed by Neu

AM. JOUR. SCI.-FIFTH SERIES, VOL. I, No. 6.-JUNE, 1921.

mann, Weber, and Helmholtz. The very general form of Helmholtz's theory appealed to him greatly, and he takes delight in showing how it contains as special cases most of the other theories proposed, including Maxwell's formulation of the results of Faraday's researches. Helmholtz's attempts to discriminate experimentally between various somewhat discordant view-points did not seem to him very conclusive, but his admiration for Hertz's genius knew no bounds. He lays particular emphasis on Hertz's zeal in following up every unexplained phenomenon to its source, mentioning in particular the discovery of the effect of ultra-violet light on the conductivity of the spark gap. His point of view throughout is that of the older British school of physicists, and it is evident that at this date the "ether" was very real to him.

During the five years following the completion of his doctor's thesis, Professor Bumstead's heavy teaching schedule left him little time for research. His interest in electrodynamics, however, was always keen, and in 1902 he published a short paper in which he showed how Maxwell's equations completely accounted for an anomaly in connection with reflection of electric waves which had been causing considerable discussion among experimentalists. If standing waves are set up on a pair of parallel guide wires terminating in a conducting plane at right angles to their length, the node in electric intensity found at the end of the wires is at a distance from the nearest node on the wire agreeing with the distances between other adjacent nodes. If, however, the conducting plane is removed, the loop to be expected at the free end of the wires is found to be at a distance from the nearest node somewhat less than a quarter wave-length. Bumstead showed that the introduction of a fictitious magnetic conductivity into Maxwell's equations established a close correspondence between this case and the well-understood arrangement in which the ends of the parallel conductors are united by a short connecting wire.

The year following the appearance of this paper, there fell on him the sad duty of writing the obituary of his friend and teacher, J. Willard Gibbs. His interest in and knowledge of mathematical physics enabled him to prepare an appreciation of the great physicist which could have been equalled by few of his contemporaries. Shortly

after, he edited, in collaboration with Dr. Van Name, Gibbs' collected works.

Bumstead's interest was greatly excited by J. J. Thomson's investigations of the properties of cathode rays and it was largely through his efforts that the successor of Maxwell and Rayleigh was persuaded to come to Yale to deliver the first Silliman lectures in May, 1903. While in New Haven Professor Thomson told him of the work being done at the Cavendish Laboratory on a radioactive gas found in water coming from deep levels, and suggested work of a similar nature at New Haven. This Bumstead carried out with the help of L. P. Wheeler. They found evidences of radioactivity not only in the gas driven off from water obtained from a well 1500 feet deep near New Milford, Conn., but also in that boiled off from surface water drawn from one of the New Haven city reservoirs. A comparison of the rate of decay of the soil-water gas with that of radium emanation showed the two to be identical. The rate of diffusion of the emanation through a porous plate was determined, and found to be about four times that of carbon dioxide. This led to an atomic weight of 180, which was, perhaps, the most reliable value which had been obtained up to that time, and, considering the difficulties of the experiment, surprisingly close to the value accepted today.

The winter 1904-5 Bumstead spent in England carrying on experimental work in the Cavendish Laboratory. This year's work led to the publication of two papers, of which the second, on the heating effects produced by Röntgen rays in metals, excited a great deal of interest. This investigation was undertaken at the time when the attention of the whole world was focused on the brilliant researches of Rutherford on atomic disintegration. Physicists were particularly interested in investigating the possibility of hastening radioactive disintegration by suitable external conditions, and in searching for new sources of radioactivity. However, every effort to control the rate of decay seemed to be in vain. From the lowest to the highest extremes of temperature, under all conditions of electromagnetic excitation, radioactive transformation went on at the same invariable rate. Bumstead's investigation consisted in measuring the heat produced in lead and zinc when Röntgen rays are equally absorbed in the two metals. His experiments seemed to lead to the very surprising result that heat developed in