378 JAMES WATT. 



the machine constructed by that engineer in 1698, to that 

 of his predecessors, although he introduced some essential 

 modifications into it ; that, amongst others, of generating 

 the steam in a separate vessel. Although it may signify 

 little relative to principle whether the steam be generated 

 from the same water that is to be elevated and in the 

 same caldron where it is to act, or from a separate vessel 

 to be admitted at will through a tube of communication 

 furnished with a tap above the fluid that is to be expelled, 

 it is not so in practice. Another alteration, still more 

 useful and worthy of special mention, equally due to Sa- 

 very, will be more appropriately treated of in the article 

 that we shall devote in the sequel to the labours of Papin 

 and Newcomen. 



Savery had entitled his work The Miner's Friend. 

 But the miners did not show themselves sensible of 

 his politeness. With only one exception, none of them 

 ordered his machine. They have been used only to dis- 

 tribute water through various parts of palaces and coun- 

 try houses, parks and gardens ; recourse has been had to 

 them only to overcome a difference of levels of twelve or 

 fifteen metres. We must keep in mind, however, that 

 the danger of explosion would have been very great, if 

 the immense power had been given to this apparatus 

 that the inventor asserted they could bear. 



Marquis of Worcester did actually make an " apparatus " to drive 

 water up by fire; and Cosmo de Medici, Grand Duke of 'Tuscany, de- 

 scribes in his Diary that he saw it in operation at Vauxhall, in the 

 year 1656, " went beyond the palace of the Archbishop of Canter- 

 bury, to see an hydraulic machine invented by my Lord Somerset, 

 Marquis of Worcester. It raises water more than forty geometrical 

 feet by the power of one man only ; and in a very short space of time 

 will draw up four vessels of water through a tube or channel not more 

 than a span in width." Savery' s engine was an improvement upon 

 this by the introduction of a vacuum. Translator, 



