Note 806 — Chapter V · (continued 2)

On the obligations of Watt to Black, compare Brougham's Life of Watt (Brougham's Works, vol. i. pp. 25, 36–38, edit. Glasgow, 1855), with Muirhead's Life of Watt, second edit. London, 1859, pp. 66, 83. At p. 301, Mr. Muirhead says of Watt, that ‘his principal inventions connected with the steam-engine, with all their prodigious results, were founded, as we have seen, on the attentive observation of great philosophical truths; and the economy of fuel, increase of productive power, and saving of animal labour, which gradually ensued, all originated in the sagacious and careful thought with which he investigated the nature and properties of heat.’ But whatever investigations Watt made into heat, he discovered no new law respecting it, or, at all events, no new law which is large enough to be noted in the history of thermotics, considered purely as a science, and apart from practical application. Mr. Muirhead, in his interesting work which I have just quoted, has published (pp. 484–486) some remarks made on the subject by Watt, several years after the death of Black, which, though perfectly fair and candid, show that Watt had a rather confused notion of the real difference between an invention and a discovery.