438 JAMES WATT. 



lei ray, infinitely diluted with the solar light that falls on 

 the first surface, issues from the second surface, diverging 

 and with a sensible breadth, it is because the glass sepa- 

 rates that which, in the white pencil, was by its nature 

 unequally refrangible." These words are nothing but a 

 literal translation of the known experiment of the pris- 

 matic solar spectrum. This translation, however, had 

 escaped an Aristotle, a Descartes, a Robert Hooke. 



Without departing from the subject, let us come to 

 some arguments which will lead in a still more direct line 

 to the point. The theory conceived by Watt of the com- 

 position of water reaches London. If it had been accord- 

 ing to the ideas of those times, as simple, as self-evident 

 as it appears to us now, the counsel of the Royal Society 

 would not have failed to adopt it : but its strangeness 

 made them doubt the correctness of Priestley's experi- 

 ments. They went so far as to laugh at it, said De Luc, 

 as at the explanation of the golden tooth. 



A theory, the conception of which did not present any 

 difficulty, would certainly have been despised by Caven- 

 dish. But recollect with what eagerness, under the in- 

 spiration of that man of genius, Blagden claimed the 

 priority of it against Lavoisier. 



Priestley, to whom a great part of the honour of Watt's 

 discovery belonged, Priestley, whose affectionate sen- 

 timents for the celebrated engineer cannot be doubted, 

 wrote to him, under date of the 29th April, 1783, 

 " Look with surprise and indignation at the drawing of 

 an apparatus, by the aid of which I have irrevocably 

 undermined your beautiful hypothesis" 



In conclusion, an hypothesis at which they laughed in 

 the Royal Society ; which made Cavendish emerge from 

 his habitual reserve ; which Priestley, laying all self-love 



