COMMEMORATION OF PROF. HENRY A. ROWLAND. 747 



Time will not allow further expositions of the important conse- 

 quences of his invention of the ruling- engine and the concave grating. 



Indeed, the limitations to which 1 must submit compel the omission 

 of even brief mention of man\' interesting and valua1)le investigations 

 relating to other subjects begun and tinished during these 3'ears of 

 activity in optical research, many of them by Rowland himself and 

 many of them b}^ his pupils, working out his suggestions and con- 

 stantly stimulated b}- his enthusiasm. A list of titles of papers 

 emanating from the ph3^sical laborator}' of the Johns Hopkins 

 University during this peried would show somewhat of the great 

 intellectual fertility which its director inspired, and would show, 

 especially, his continued interest in magnetism and electricit}^, leading 

 to his important investigations relating to electric units and to his 

 appointment as one of the United States delegates at important inter- 

 national conventions for the better determination and definition of 

 these units. In 1883 a committee appointed by the Electrical Congress 

 of 1881, of which Rowland was a member, adopted 106 centimeters as 

 the length of the mercury column equivalent to the absolute ohm, but 

 this was done against his protest, for his own measurements showed 

 that this was too small b}- al)out three-tenths of 1 per cent. His 

 judgment was confirmed by the chamber of delegates of the Interna- 

 tional Congress of 1893, of which Rowland was himself president, 

 and by which definitive values were given to a S3^stem of international 

 units. 



Rowland's interest in applied science can not be passed over, for it 

 was constant^ showing itself, often, perhaps, unbidden, an uncon- 

 scious bursting forth of that strong engineering instinct which was 

 born in him, to which he often referred in familiar discourse, and 

 which would unquestionabh^ have brought him great success and dis- 

 tinction had he allowed it to direct the course of his life. Although 

 everj^where looked upon as one of the foremost exponents of pure 

 science, his abilitj" as an engineer received frequent recognition in his 

 appointment as expert and counsel in some of the most important 

 engineering operations in the latter part of the century. He was an 

 inventor, and might easih' have taken first rank as such had he chosen 

 to devote himself to that sort of work. During the last few 3'ears of 

 his life he was much occupied with the study of alternating electric 

 currents and their application to a system of rapid telegraphy of his 

 own invention. A year ago his system received the award of a grand 

 prix at the Paris Exposition, and oidy a few weeks after his death the 

 daih' papers published cablegrams from Berlin announcing its com- 

 plete success as tested between Berlin and Hamburg, and also the 

 intention of the German postal department to make extensive use 

 of it. 



But behind Rowland, the profound scholar and original investigator, 

 the engineer, mechanician, and inventor, was Rowland the man. and any 



