1 7 o HER OES OF IN VENTION AND DISCO VER Y. 



JOSEPH BLACK. 



Joseph Black, the famous chemist, was bom in France iii 

 1728. He was educated at the Universities of Glasgow and 

 Edinburgh, In 1756 he was appointed Professor of Anatomy 

 and Lecturer on Chemistry at Glasgow. It was during his 

 residence at Glasgow that he made and established his dis- 

 covery of latent heat 



The following most interesting account of one of the prin- 

 cipal discoveries in modern science is from a biographical 

 memoir prefixed by Professor Robinson to Dr. Black's Lec- 

 tures : — 



"It seems to have been between the years 1759 and 1763 

 that his speculations concerning heat, which had long occupied 

 his thoughts, were brought to maturity. And when it is con- 

 sidered by what simple experiments, by what familiar observa- 

 tions, Dr. Black illustrated the laws of fluidity and evaporation, 

 it appears wonderful that they had not long before been ob- 

 served and demonstrated. They are, however, less obvious 

 than might at first sight be imagined ; and to have a clear and 

 distinct conception of those seemingly simple processes oi 

 nature required consideration and reflection. 



" If a piece of wood, a piece of lead, and a piece of ice are 

 placed in a temperature much inferior to that of the body, and 

 if we touch the piece of wood with the hand, it feels cold ; if 

 we touch the piece of lead, it feels colder still ; but the piece of 

 ice feels colder than either. Now, the first suggestion of sense 

 is that we receive cold from tlie wood, that we receive more 

 from the lead, and most of all from the ice ; and that the ice 

 continues to be a source of cold till the whole be melted. But 

 an inference precisely the contrary to all this is made by him 



