(b. Wilsden, Yorkshire, England, 22 March 1868; d. Ealing, London, England, 24 June 1940)
Alfred Fowler was the eighth child and seventh son of Hiram Fowler and his wife, Eliza Hill Fowler. The family was of working-class origin, and Alfred attended elementary schools at Keighley, the largest neighboring town, to which the family moved about 1876. In 1880 he obtained a scholarship to the local trade and grammar school; in 1882, with the aid of a Devonshire exhibition, he proceeded to the Normal School of Science (later the Royal College of Science, now forming a constituent of the Imperial College of Science and Technology) at South Kensington. Here, after a successful career as a student of mechanics, he obtained an appointment as a teacher in training under Norman Lockyer, who had shortly before become director of the Solar Physics Observatory at South Kensington and lecturer in astronomy at the Normal School of Science. This began Fowler’s close association with Lockyer and participation with him in the then new field of the application of the spectroscope to astronomy. The association lasted until Lockyer’s retirement from the Royal College of Science in 1901, whereupon Fowler succeeded him as assistant professor, and later as professor, of astrophysics. He held this post until 1923, when he was appointed one of the first two Yarrow research professors of the Royal Society. He was thus enabled to continue research at the college but was relieved of teaching duties (other than the direction of research students). He remained there until his retirement in 1934.
In 1892, Fowler married Isabella Orr, who survived him, as did a daughter and a son. His life, apart from his astrophysical work, was uneventful, his interests being concentrated almost entirely on his scientific research and duties arising from his involvement in the organization of science. He successfully directed his students’ activities, and many who later achieved distinction in spectroscopy owed much to their early research under his guidance. When the International Astronomical Union was formed in 1919, Fowler became its first general secretary, a position he retained until 1925. The original statutes of the union were drafted by Fowler and adopted almost without change.
During his association with Lockyer, much of Fowler’s work was incorporated into that of the senior man, and it was not until he became an independent investigator that his own abilities began to be recognized. Consequently, honors came to him slowly at first, but later in good measure. Temperamentally he was a striking contrast to Lockyer; and their association, although not without occasional misunderstandings, was in many respects fortunate for both. Lockyer’s impetuous development of an idea until it became a hypothesis too massive for its frail observational basis was tempered, and often supported, by Fowler’s insistence on the primacy of facts and his great skill in acquiring them; while Fowler never forgot, or failed to acknowledge, the inspiration he received, especially in his early days, from Lockyer’s enthusiasm. Fowler’s life was marked by a quiet integrity and amiability that endeared him to all his associates.
His contributions to astrophysics were based on an exceptionally intimate knowledge of the characteristic spectra of the elements, acquired during his apprenticeship with Lockyer, and an almost uncanny skill in recognizing the identity of celestial spectra and those obtained under vastly different laboratory conditions. These abilities enabled him to assign the band spectra yielded by the cool stars (type M) to titanium oxide, to detect the presence of magnesium hydride in sunspots, to identify bands observed in comet tail spectra with those of low-pressure carbon monoxide, and, with R. J. Strutt (later Lord Rayleigh), to prove that the termination of solar and stellar spectra in the near ultraviolet was caused by ozone in the earth’s atmosphere.
His outstanding achievements, however, followed the sudden enlargement of interest in spectroscopy created by Bohy’s successful theory of the origin of spectra that appeared in 1913. This made possible a theoretical analysis of spectra that demanded a knowledge of their details, in which Fowler was unrivaled. His work as Lockyer’s assistant had involved not only investigations of laboratory spectra from all available sources and of as great a range of celestial spectra as the atmospheric conditions at South Kensington allowed, but also participation in several expeditions to observe total eclipses of the sun. Moreover, under the influence of Lockyer’s dissociation hypothesis Fowler had acquired a large amount of information on the variation of spectra with physical conditions, although the general disfavor extended to that hypothesis had discouraged its publication.
The Bohr theory showed the significance and value of such data, and Fowler accordingly took a leading part in the subsequent elucidation of the structure of the various atoms from the characteristics of their spctra. As a first reaction to the Bohr theory he pointed out a discrepancy between the wavelength of the so-called cosmic hydrogen line at λ4686 Å, which he had observed in the spectrum of the sun’s chromosphere, and that calculated by Bohr as λ4688 Å an ascribed to ionized helium—an anomaly that resulted in the first refinement of the theory, in which account was taken of the finite ratio of the masses of the proton and the electron. There ensued a continuous interaction between theory and observation in which Fowler played a leading part.
It is fortunate that the period during which spectroscopy stood in the vanguard of physical advance coincided with that in which Fowler, with unique experience and possession of the necessary observational data, could place such data, with no preconceptions, at the service of theoretical investigators. His career offers one of the best examples we have of the variety of possible interactions of theory and observation in the advancement of science.
Fowler wrote little beyond his original papers, mainly in Proceedings of the Royal Society and Monthly Notices of the Royal Astronomical Society. “I was too keenly interested in research,” he wrote, “to give much thought to the writing of books.” Nevertheless, he published a handbook entitled Popular Telescopic Astronomy (London, 1895), with the subtitle How to Make a 2-inch Telescope and What to See With It, and he contributed about 190 pages on “Geometrical Astronomy and Astronomical Instruments” to a volume entitled The Concise Knowledge Astronomy (London, 1896). His only work on his chief specialty was Report on Series in Line Spectra (London, 1922), which contains all the data then available on the regularities in spectra (much of which he had brought to light) together with a general account of the subject. He contributed a chapter to Life and Work of Sir Norman Lockyer, by T. Mary Lockyer and Winifred L. Lockyer (London, 1928), in which he gives some account of his relations with Sir Norman.
No biography of Fowler exists; the notice in Obituary Notices of the Royal Society, 1940 is probably the fullest that has appeared.