HEAT OR CALORIC. 93 



water was reiterated, as likewise in due succession the other steps of 

 the process, as above stated." 



Of Newcomen's Engine. 



" The great objection to Savary's engine, was the waste of steam 

 arising from its entrance, over the water, into a cold moist chamber. 

 So great is the power of cold water in condensing steam, that had 

 the steam been introduced, below the water, it could not have been 

 expelled until ebullition should have been excited ; but heat, being; 

 propagated downwards in liquids with extreme difficulty, the steam 

 entering from above was not condensed so rapidly as to paralyze the 

 engine." 



" To diminish the very great loss sustained in the engine of Sa- 

 vary, Newcomen, instead of causing the vacuum produced by the 

 condensation to act directly upon water, contrived that it should act 

 upon a piston, moving, air tight, in a large cylinder, like a pump 

 chamber. The piston was attached to a large lever, to the end of 

 which, on the other side of the fulcrum, a pump rod and a weight 

 were fastened. By the vacuum arising from the condensation, the 

 piston, being exposed to the unbalanced pressure of the atmosphere, 

 was forced down to the bottom of the cylinder, drawing up, of course, 

 the rod and weight at the other end of the lever." 



"The cylinder being replenished with steam, the weight on the 

 beam drew up the piston in the cylinder, and pushed down the pump 

 rod, and thus by the alternate admission and condensation of steam, 

 the piston and pump rod were made to undergo an alternate motion, 

 by which the pump, actuated by the rod, was kept in operation. 

 Although less caloric was wasted by Newcomen's engine than by 

 Savary's, there was still great waste, as the cylinder was to be heated 

 up to the boiling point each time that steam was admitted, and to 

 be cooled much below that point as often as condensation was ef- 

 fected." 



In Watt and Bolton's Engine,* steam from the boiler lifts the pis- 

 ton, and steam let in above, depresses it ; condensation of the steam 

 taking place at the same time, by communication with a cold vacuum,, 

 connected with an air pump ; thus the stroke and condensation are 

 alternate, the cylinder is kept constantly hot, and the condenser cold y 

 by water pumped in by the working machinery, from below ; the 

 hot water, formed from the condensed steam, is returned to the boiler. 



* This engine, the most splendid present ever made by science to the arts, is, ic 

 common with other steam engines, far from using the whole power that is genera- 

 ted ; for Clement and Desormes conclude, from their own experiments that the 

 best steam engines have brought to bear not more than one twelfth part of the 

 power of steam, as calculated by theory. Then. I. 85, 5th Edit. 



