26 



THE POPULAR SCIENCE MONTHLY. 



particularly the deep pits of Cornwall, free from water, and the failure 

 of every attempt previously made to provide effective and economical 

 pumping machinery, were noted by Savery, who, July 25, 1698, pat- 

 ented the design of the first engine which ever was actually employed 

 in this work. 



Thomas Savery. 



A working model was submitted to the Royal Society of London, 

 in 1699, ' and successful experiments were made with it. 



This engine is shown in Fig. 8, as described by Savery himself in 

 1702, in the "Miner's Friend." 



L L is the boiler, in which steam is raised, and through the pipes 

 it is alternately let into the vessels P P. 



Suppose it to pass into the left-hand vessel first. The valve M 

 being closed and r being opened, the water contained in Pis driven 

 out and up the pipe S to the desired height, where it is discharged. 



The valve r is then closed, and also the valve in the pipe 0. The 

 valve M is next opened, and condensing water is turned upon the exte- 

 rior of P by the cock F, leading water from the cistern X. As the 

 steam contained in P is condensed, forming a vacuum, a fresh charge 

 of water is driven by atmospheric pressure up the pipe T. 



Meantime, steam from the boiler has been let into the right-hand 

 vessel P, the cock W having been first closed and R opened. The 

 charge of water is driven out through the lower pipe and the cock R, 

 and up the pipe S as before, while the other vessel is refilling prepara- 

 tory to acting in its turn. 



1 " Transactions of the Royal Society," 1699. 



