328 BLACK. 



beautiful example of strict inductive investigation since 

 the ' Optics' of Sir Isaac Newton. His fervent ad- 

 miration of that masterly work was indicated by his 

 giving it to Professor Robison, then a student, and 

 desiring him to " make it the model of all his studies," 

 recommending him at the same time a careful study of 

 the mathematics. It appears that this important 

 inquiry concerning the alkaline earths, the results 

 of which were destined to change the face of chemical 

 science, was suggested by the attempts then making to 

 rind a solvent for the stone. I distinctly recollect Dr. 

 Black, in his lectures, prefacing the admirable and 

 most interesting account which he gave of his dis- 

 coveries, with the statement that the hopes of finding 

 a solvent which should not, like the caustic alkalies, 

 destroy the substance of the bladder in melting the 

 stone, first led him to this investigation. Professor 

 Robison has given a note from his memorandum-book 

 indicating that he had at first fallen into the notion of 

 alkalies, when treated with quicklime, deriving from 

 it their caustic quality ; the common belief (which 

 gave rise to the term caustic) being that lime obtained 

 from the fire the quality of growing extremely hot, 

 even to ignition when united with water. But expe- 

 riment soon corrected this idea ; for, having exposed 

 the caustic or quicklime to the air till it became mild, 

 he says, " Nothing escapes (meaning no fire or heat) ; 

 the cup rises considerably by absorbing air." Another 

 observation on the comparative loss of weight sustained 

 by chalk when calcined (in the fire), and when dis- 

 solved in an acid, is followed by the account of a 

 medical case, which the Professor knew to have 



