SECT. ,.] THE STEAM ENGINE. 7 



steam vessel. To prevent the risk of bursting the boiler, he applied the steelyard 

 safety valve V ; invented by Papin for his digester. The cocks were managed by 

 hand ; and, to supply the boiler with water, he had a small boiler adjoining to 

 heat water for the use of the large one, and thus prevent the loss of time which 

 must have occurred on refilling it with cold water. 



Several engines for raising water appear to have been erected according to 

 Savery's plan, and to have succeeded tolerably where the water had not to be 

 raised more than forty feet ; but this was not sufficient for mines, where a new and 

 powerful machine was most wanted. 



The new principles, introduced into the steam engine by Savery, consist of the 

 use of condensation in the steam vessel by cold applied externally. He also used a 

 method of supplying the boiler with hot water, contrived a mode of ascertaining 

 the quantity of water in the boiler, by inserting the cock g, called a gauge cock, 

 and applied the safety valve of Papin's digester as a means of preventing accidents. 



The defects of his engine are obvious. A cold vessel and cold fluid must at each 

 operation condense, and therefore waste a great quantity of steam ; and the height 

 to which water could be raised, unless by the use of such powerful steam as to 

 render it dangerous, was too limited to be applicable to mining purposes. Its 

 effect would however be vastly superior to that of the Marquis of Worcester's. 

 Whether Captain Savery did or did not know of the previous schemes, his claims 

 to original invention are certainly considerable ; and to his enthusiasm and talent 

 we undoubtedly owe the first effective steam engine. 



1698. DR. DENNIS PAPIN. 



8. Dr. Papin, professor of mathematics at Marbourg, whose former project I 

 have noticed (art. 6), is said to have made many experiments on raising water by 

 the force of fire, in 1698, by the order of Charles, Landgrave of Hesse ; and in 

 1707 he published a small treatise on the subject, in which he ascribes to the land- 

 grave the whole merit of the first idea of a steam engine. Papin's trials in 1698, 

 whatever they were, did not end in producing any thing in a useful shape ; and, 

 while he candidly acknowledges that Savery's scheme was not borrowed from any 

 thing done in Germany, it appears that he did not follow up his experiments till 

 after he had seen an engraving of Savery's engine, in June, 1705 ; a pretty con- 

 clusive argument, that no satisfactory results had been arrived at in these experi- 

 ments ; and there is a wide distinction between unsuccessful experiments and 

 invention. 



To do justice to the claims of Papin, it will be sufficient to describe his engine 

 in its most improved state, and as he gives it after knowing what Savery had 



