132 GREAT MEN OF SCIENCE 



We may imagine how great was the progress represented 

 by this notion as compared with the complete uncertainty 

 concerning questions of vapour pressure, which Leibniz 

 and Papin had found, until they themselves came to perceive 

 that the pressure phenomena exhibited by heated water are 

 to be ascribed to the latter and to its vapour, and not to 

 an 'expansive constituent,' which it was supposed must be 

 present in the water. It was thirty years later before Dalton 

 was able to advance the question of vapour pressure further 

 than Watt had carried it. 



The separate condenser which Watt immediately tried 

 out on a small scale proved at once satisfactory in the 

 expected manner. With it Watt's low pressure steam engine 

 was in the main invented; the other accessories necessary 

 for its good performance, such as air pump, feed pump, 

 condenser water-pump, flywheel, centrifugal governor, 

 double action of steam on both sides of the piston, occurred 

 to Watt directly - but not without his having to experience 

 the length of the stride from the invention to practical 

 production on a large scale. We are not able to follow his 

 progress in detail.^ 



Papin had been in a like position, and had gone under; 

 Watt had over him the advantage that Papin's ideas had 

 already been carried out in a large scale in the machines, 

 however imperfect, of Newcomen and Savery; while the 

 further great advantage he possessed was that of being 

 not only the inventor, but also himself the mechanic who 

 carried out the work. Nevertheless, that did not help him 

 as much as he no doubt imagined it would. It was no trifle 



1 The reader may be referred to the full account of his life given in 

 Lives of the Engineers (Boulton & Watt), by Samuel Smiles, London 1878. 

 The worst part of the difficulties which continued to threaten Watt, lay 

 in humanity's greed of gain, which made the more difficulties for him, the 

 greater the success of the machine. 'The rascality of mankind is almost 

 beyond belief was one of his remarks to Black. A later work Watt and 

 the Steam Engine, by Dickinson and Jenkins, Oxford 1927, reproduces 

 many portraits and historical machine drawings. 



