Apeil 1, 1898.] 



SCIENCE. 



449 



Nevertheless, he kept numerous data from 

 his work at Harvard, and published a num- 

 ber of astronomical papers after his removal 

 to Colby University. His special interest, 

 however, had been gradually transferred to 

 the domain of physics. In the construc- 

 tion of micrometers he early experienced 

 trouble on account of the scarcity of suit- 

 able spider webs, and this caused him to 

 undertake the etching of fine lines on glass. 

 8o successful was he in this that a large 

 number of his plates were secured by the 

 representatives of the national government, 

 and sent out for use by the observers on 

 the occasion of the transit of Venus. Dur- 

 ing his study of standards of length he 

 visited Europe, obtained authorized copies 

 of the English and French standards, and 

 brought these home with him. They were 

 then used by him as the bases of compar- 

 ison for bars which he constructed and 

 ruled, and these are now the chief stand- 

 ards in a number of the most important 

 laboratories in America. 



Immediately after his removal to Colby 

 University Professor Eogers undertook the 

 study of thirty mercurial thermometers of 

 the U. S. Signal Service pattern, and by 

 comparison with these he secured a standard 

 for the measurement of very low tempera- 

 tures. It was about this time that Michel- 

 son and Morley developed the interferential 

 comparator, and began their investigation 

 regarding the use of the wave-length of so- 

 dium as a standard of length. Professor 

 Rogers had already done much work with 

 comparators, and he soon became associated 

 with Professor Morley in the application of 

 optical methods to the determination of mi- 

 nute changes of length. After proper ad- 

 justment of apparatus the measurement of 

 almost infinitesimal expansion or contrac- 

 tion becomes possible by merely counting 

 the number of interference fringes of mono- 

 chromatic light which pass across the field 

 of view in a given period of time. In this 



way Professor Eogers determined the co- 

 efi&cient of linear expansion of Jessop steel 

 with a degree of precision never before at- 

 tained. His work in this connection was 

 presented at the Springfield meeting of the 

 Scientific Association in 1895. 



In his address last summer at the laying 

 of the corner-stone of the new physical lab- 

 oratory of Alfred University, Professor Eog- 

 ers gave a summary of the kind of work 

 which he proposed to undertake personally 

 and with the cooperation of his more ad- 

 vanced students. Prominent among the 

 subjects had in view were the study of the 

 law of expansion of metals under changes of 

 temperature, the standardization of meas- 

 ures of length, the separate measurement 

 of the effects of hot air and of the heat con- 

 veyed by radiation, the energy of heat 

 radiations as determined with the interfer- 

 ometer, the development of the construction 

 of precision screws, the practical develop- 

 ment of methods of precision in work-shop 

 operation, the investigation of the relative 

 cost and efficiency of small sources of power, 

 of the economy of various methods of heat- 

 ing, and of methods for generation of X-rays. 

 This is an excellent summary of the work 

 to which he had been devoting his energies 

 for some years past. 



In acknowledgment of his scientific work 

 Professor Eogers was elected, in 1873, to 

 membership in the American Academy of 

 Arts and Sciences at Boston. In 1880 he 

 received the honorary degree of A.M. from. 

 Yale, and during the following year he was 

 made an Honorary Fellow of the Eoyal Mi- 

 croscopical Society. In 1886 he received the 

 honorary degree of Ph.D. from Alfred Uni- 

 versity, on the occasion of the semi-centen- 

 nial of this institution, and in 1892 Brown 

 University conferred the degree of LL.D. 

 In 1895 he' was elected to membership in 

 the National Academy of Sciences. In ad- 

 dition to these recognitions of merit he was 

 made Vice-President of the American Mi- 



