254 Obituary Notices of Fellows deceased. 



his merit was soon recognized at home by his appointment in 1875 as 

 Professor of Physics in the Johns Hopkins University, the Faculty of 

 which was then being organized. 



As a preliminary to taking up the work of this new post, he spent 

 a year in Europe at various scientific centres, including several months 

 at Berlin in the Laboratory of Helmholtz. While there he made the 

 very delicate investigation of the magnetic effect of moving charges of 

 electricity, a subject of the most fundamental theoretical importance. 

 He succeeded in obtaining the positive result that was looked for, 

 though many previous investigators had failed ; but the difficulty of the 

 experiment is so great that the conclusion has since often been called in 

 question. Various subsequent experimentalists have been able to attain 

 only negative results, though using apparatus apparently more complete 

 and delicate than Rowland's. The original conclusion was however 

 confirmed by Eowland himself at Johns Hopkins in 1889 and again in 

 1900, and also more recently by others at Harvard, and Paris, and 

 elsewhere. 



On his return from Europe in 1876, much of his time was devoted 

 to planning and carrying out the equipment of the new Physical 

 Laboratory at Baltimore. In its arrangement great prominence was 

 given to the equipment of the workshop in machinery, tools, and 

 assistants. Eowland was perhaps the first to recognize the great 

 importance of a well-equipped workshop for the execution of original 

 investigation, and he intended from the first that most of his energies 

 should be directed in this channel. 



His first important investigation at his new post was the 

 determination of the absolute value of the British Association unit of 

 electrical resistance. According to Kohlrausch's results in 1870, the 

 standards constructed by the Electrical Standards Committee of the 

 British Association in 1863-4, to represent 10 9 C.G.S. units of resist- 

 ance, were 2 per cent, too high, while according to the work of Lorenz 

 in 1873 they were 2 per cent, too low. Rowland's paper contains an 

 able criticism of the old experiments, and a clear account of the way 

 in which he was enabled to secure results which were probably the 

 most accurate achieved up to that time. His value for the British 

 Association unit was '9912 x 10 9 C.G.S., which is within 0-5 per cent, 

 of the value now adopted. His next work was the redetermination of 

 the value of the Mechanical Equivalent of Heat, which was presented 

 to the American Academy in 1879, following close on Joule's final 

 results of 1878. This paper, in which he repeats a familiar laboratory 

 experiment on something of an engineering scale, well illustrates his 

 constructive ability in the design of apparatus, and his experimental 

 insight into the inherent difficulties of a problem and the details 

 requiring special attention for the obtaining of accurate determinations. 



