CAPTIVE MOLECULES 



produced by condensation, and the same process was 

 repeated. By using two oval steam vessels, which would 

 act alternately one drawing water from below, while 

 the other was forcing it upwards, an uninterrupted 

 discharge of water was produced. Owing to the danger 

 of explosion, from the high pressure of the steam 

 which was used, and from the enormous waste of heat 

 by unnecessary condensation, these engines soon fell 

 into disuse." 



This description makes it obvious that Savery had 

 the clearest conception of the production of a vacuum 

 by the condensation of steam, and of the utilization 

 of the suction thus established (which suction, as we 

 know, is really due to the pressure of outside air) to 

 accomplish useful work. Savery also arranged this 

 apparatus in duplicate, so that one vessel was filling with 

 water while the other was forcing water to the delivery 

 pipe. This is credited with being the first useful ap- 

 paratus for raising water by the combustion of fuel. 

 There was a great waste of steam, through imparting 

 heat to the water, but the feasibility of the all-important 

 principle of accomplishing mechanical labor with the 

 aid of heat was at last demonstrated. 



As yet, however, the experimenters were not on the 

 track of the method by which power could be advan- 

 tageously transferred to outside machinery. An effort 

 in quite another direction to accomplish this had been 

 made as early as 1629 by Giovanni Branca, an Italian 

 mathematician, who had proposed to obtain rotary 

 motion by allowing a jet of steam to blow against the 

 vanes of a fan wheel, capable of turning on an axis. 



[87] 



