THE HISTORY OF 



[SECT. i. 



consisted of a furnace and boiler B ; from the latter two pipes, provided with cocks 

 C, proceeded to two steam vessels S, which had branch pipes from a descending 



FIG. 2. 



main D, and also to a rising main pipe A ; each pair of branch pipes had valves 

 a, b, to prevent the descent of the water raised by the condensation or by the force 

 of steam. Only one vessel, S, is shown, the other being immediately behind it. 

 One of the steam vessels being filled with steam, condensation was produced by 

 projecting cold water, from a small cistern E, against the vessel ; and into the 

 partial vacuum made by that means, the water, by the pressure of the atmosphere, 

 was forced up the descending main D, from a depth of about twenty feet ; and, on 

 the steam being let into the vessels again, the valve b closed, and prevented the 

 descent of the water, while the steam having acquired force in the boiler, its 

 pressure caused the water to raise the valve a, and ascend to a height proportional 

 to the excess of the elastic force of the steam above the pressure of the air. 



Captain Savery afterwards simplified this engine considerably, by using only one 



