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POPULAR SCIENCE MONTHLY. 



he made contributions of great im- 

 portance. His early work on magnetic 

 permeability attracted the attention of 

 Maxwell, and his subsequent research 

 on the magnetic effect of moving elec- 

 trostatic charges was fully appreciated 

 by Helmholtz, in whose laboratory it 

 was carried out. Sixty-three papers 



absolute wave-lengths were also the 

 results of long-continued and careful 

 detailed work, but they were made pos- 

 sible by the important work on screws, 

 tne construction of the famous dividing 

 engine, and the great discovery of the 

 use of a concave grating. 



Rowland was fortunate in being 



Geo. F. FlTZCiERAI.D. 



on magnetism and electricity are in- 

 cluded in the memorial volume. The 

 research on the mechanical equivalent 

 of heat was somewhat routine in char- 

 acter, determining with the most pains- 

 taking accuracy one of the most im- 

 portant physical constants. Tlie pho- 

 tographic map of the normal solar 

 spectrum and the determination of 



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 op- 

 portunity for research freely granted, 

 and the university was fortunate and 

 wise in calling a man who added so 

 greatly to its ropulation and influence. 

 It is told of Rowland that when, in a 



