50 Henry Riddell on 



years ago, till the end of the first quarter of the 19th century. I 

 shall finish up by a short biography of Joseph Black as a man, 

 and I hope to leave you feeling as I do, that he passed through 

 life as a gentleman, thoughtful for his students, his patients and 

 his friends ; a loving son and brother and a faithful comrade. 



To understand Black's services to science it is necessary to call 

 to mind the condition of learning in physics and chemistry at the 

 time his work was done, say, from 1750 to 1770. In those days 

 Natural Philosophy was a term which covered all such branches 

 of science as Physics, Chemistry, and those almost quite un- 

 developed studies, Greology, Biology and Zoology, and it is there- 

 fore not at all surprising to find that, as professor of chemistry. 

 Black lectured upon the earth and the theories developed by his 

 great crony, Hutton, and that his experiments in heat were also a 

 chief part of his work. T, of course, remember that my great 

 teacher. Dr. Thomas Andrews, really was a physicist teaching 

 chemistry, rather than a chemist experimenting in physics. 



In Black's earlier days there was little understanding of the 

 relation between elementary bodies. The birth of Daltoii, the 

 originator of the conception of atomic weights, took place twelve 

 years after Black had presented the famous Thesis written for his 

 degree. It was in 1754 that Black wrote this thesis, while it 

 was in 1766 that Cavendish discovered hydrogen; in 1772 

 Eutherford separated nitrogen, and in 1774 oxygen was dis- 

 covered by Priestly, the discovery which is really the foundation 

 stone of modern chemistry. There were some observations earlier 

 than Black's that might have given the clue, but they were not 

 followed up, and till his time the fact that a gaseous element 

 might exist in a solid form in a stone was totally unsuspected. 

 Chemistry was then chiefly taught as a medical subject, and 

 inseparably connected with the study of medicine, so that it is 

 not strange to find the professorship of Anatomy and Chemistry 

 held by the same man. Black was instituted professor of 

 Anatomy and lecturer in Chemistry in Glasgow in 1756, and began 

 there that long period of teaching chemistry which exercised such 



