JAMES WATT 135 



certainty; the age of steam began. Watt was able to exper- 

 ience the promising beginning of all this, and as he grew 

 older he was able to rejoice in greater and greater success; 

 even the headaches from which he had suffered greatly 

 during the period of his highest activity, at last left him, and 

 he enjoyed a comfortable old age. He had married twice - 

 his first wife died early - and he lived to the age of eighty- 

 three. 



We must not forget that Watt also took part in pure 

 scientific research. As a friend of Priestley, he was concerned 

 in the discovery of the composition of water which was 

 then in progress, and was completed by Cavendish; water 

 had hitherto been regarded as an element.^ Very notable 

 is the complete clarity with which he deals with the concept 

 of work, in which he makes a considerable advance upon 

 Leonardo and Stevin; however, in the development of the 

 steam engine, this must appear almost self-evident. He 

 measures the work done in the cylinder of his engines quite 

 rightly by the product of pressure and volume, which here 

 takes the place of the product of force and distance. For 

 this purpose he constructed a special instrument, which 

 could be connected to the cylinder, his so-called indicator. 

 Also, the measure at present used for work done in unit 

 time, the horsepower, was introduced by him. 



Watt received an impressive memorial in Westminster 

 Abbey; the inscription praises him as benefactor of humanity. 

 He certainly deserves the term as far as he was concerned. 

 He, as the inscription says, 'increased the powers of man.* 

 They are certainly increased ten times to-day by means of 

 the steam engine. But why do we not find that man has 

 become happier and on a higher spiritual level through 

 Watt's present to them, which enables natural force when 



1 The reader may be referred for an account of Cavendish's work to 

 the Life, by G. Wilson, 1848; also to the Collected Papers, Cambridge, 

 1921. 



