he made contributions of great importance. His early work on magnetic permeability attracted the attention of Maxwell, and his subsequent research on the magnetic effect of moving electrostatic charges was fully appreciated by Helmholtz, in whose laboratory it was carried out. Sixty-three papers on magnetism and electricity are included in the memorial volume. The research on the mechanical equivalent of heat was somewhat routine in character, determining with the most painstaking accuracy one of the most important physical constants. The photographic map of the normal solar spectrum and the determination of absolute wave-lengths were also the results of long-continued and careful detailed work, but they were made possible by the important work on screws, the construction of the famous dividing engine, and the great discovery of the use of a concave grating.
Rowland was fortunate in being called to the Johns Hopkins University at its organization, where for the first time in America the value of original research was fully appreciated and opportunity for research freely granted, and the university was fortunate and wise in calling a man who added so greatly to its reputation and influence. It is told of Rowland that when, in a
