840 POPULAR SCIENCE MONTHLY. 



Rogers also made a careful investigation and estimation of the 

 probable total production of the Consolidated Virginia and Cali- 

 fornia Mine in Nevada. He was further, from 1874 to 1879, or for 

 about six years, a member every year of the Annual Assay Com- 

 mission. He was for twelve years one of the chemists to make 

 an analysis and daily photometric test of the illuminating gas 

 supplied to Philadelphia. 



In 1877 Prof. Rogers was elected Professor of Medical Chemis- 

 try and Toxicology in Jefferson Medical College ; and, to accept 

 the offer, resigned the position which he had for a quarter of a 

 century held in the university. His entrance into this institution 

 was the occasion of a flattering demonstration at the time of the 

 opening of the course of 1877-78 with an introductory lecture. 

 "It was estimated that not less than twelve hundred physicians, 

 students, and others were crowded into the hall. At the conclu- 

 sion of the lecture a silver vase was presented to him as a token 

 of the respect felt for him by the great class of medical students." 



Prof. Rogers became a member of the Academy of Natural 

 Sciences of Philadelphia in 1837 ; was interested in its proceedings 

 through most of his life ; attended its meetings at irregular inter- 

 vals for many years in succession ; participated in its discussions, 

 and delivered lectures to promote its interests. Many of his 

 verbal communications are noted in its proceedings from 1859 to 

 1862. He was a member of the Franklin Institute from April, 

 1838, except when living away from Philadelphia ; became a life 

 member in 1855 ; one of the Board of Managers in 1857 ; was one 

 of the vice-presidents for seventeen years from 1858 ; was chosen 

 president in 1875 ; and on retiring from that ofhce in 1879 was 

 returned to the Board of Managers for the rest of his life. " He 

 was particularly active in the work of the institute, delivered 

 courses of lectures on chemistry before its classes, assisted in the 

 management of its public exhibitions, served on several of its 

 standing and on many of its special committees, the most notable 

 of which were one on tests of the efficiency of dynamo- electric 

 machines, and another on the dangers of electric lighting." At 

 the celebration of the semi-centennial anniversary of the founda- 

 tion of the society, February 5, 1874, he delivered an address on 

 the history of scientific discoveries and their practical applica- 

 tions in the half century, in which he pointed out how the work 

 of the institute had contributed to the progress of science and 

 the diffusion of knowledge. 



He was elected a member of the American Philosophical Soci- 

 ety in 1855 and a member of its Council in 1859. He was a fre- 

 quent attendant at its meetings, served on several of its commit- 

 tees, and often took part in its discussions. He was less often 

 present at the meetings of the College of Physicians, of which he 



