M. Arago's Biographical Memoir of James Watt. 273 



narrowest justice is all that one can expect from a rival or 

 competitor, however high may have been his previous reputa- 

 tion. Cavendish would scarcely listen to his men of business, 

 when they came to consult him concerning the disposal of his 

 prodigious wealth ; but we may perceive, he had not the same 

 indifference concerning his scientific property. We ought to 

 insist, therefore, in demanding, after the example of the judges 

 in courts of law, that the historians of science should never 

 receive, as valid titles of property, any other than written, 

 I should perhaps add published, titles. It is then, and then 

 only, that an end will be put to those constantly recurring 

 disputes which are usually agitated at the expense of national 

 vanity ; and it is then only that the name of Watt will assume 

 that distinguished place in the history of chemistry to which 

 it is justly entitled. 



The solution of a question of priority, where, as in the pre- 

 sent instance, it is grounded upon the most attentive examina- 

 tion of printed memoirs, and a minute comparison of dates, 

 possesses all the characters of a complete demonstration. 

 Nevertheless, it may not be superfluous to notice slightly, va- 

 rious difficulties to which respectable individuals have seemed 

 to me to attach some importance. 



How, it has been said, can it be admitted that, amidst the 

 immense turmoil of commercial business, — engaged with a mul- 

 titude of law-suits, and obliged to provide, by the ingenuity of 

 every passing day, for the difficulties of an infant discovery. 

 Watt could have found time to follow, step by step, the 

 progress of chemistry, to originate experiments, and propose 

 explanations which even the masters of the science had not 

 foreseen ! To this difficulty, I make a very short and con- 

 clusive answer. I have now in my possession the copy of an 

 active correspondence, relating principally to chemistry, which 

 Watt maintained during the years 1782-3, and 4, with Priest- 

 ley, Black, Deluc, the engineer Smeaton, Gilbert Hamilton 

 of Glasgow, and Fry of Bristol. 



Another objection, proceeding from a profound knowledge 

 of the human heart, appears more specious. Since the disco- 

 very of the composition of water is one that ranks at least as 

 high as the admirable inventions combined in the steam-en- 



