CAPTIVE MOLECULES 



so that they are strengthened by the force within them, 

 and the one to fill after the other, I have seen the water 

 run like a constant stream, forty feet high: one vessel 

 of water, rarefied by fire, driveth up forty of cold water; 

 and the man that tends the work is but to turn two 

 cocks, that one vessel of water being consumed, another 

 begins to force and refill with cold water, and so suc- 

 cessively; the fire being tended and kept constant, 

 which the self-same person may likewise abundantly 

 perform in the interim, between the necessity of turn- 

 ing the said cocks." 



It is unfortunate that the Marquis did not give a more 

 elaborate description of this remarkable contrivance. 

 The fact that he treats it so casually is sufficient evidence 

 that he had no conception of the possibilities of the 

 mechanism; but, on the other hand, his description 

 suffices to prove that he had gained a clear notion of, 

 and had experimentally demonstrated, the tremendous 

 power of expansion that resides in steam. No example 

 of his steam pump has been preserved, and historians 

 of the subject have been left in doubt as to some de- 

 tails of its construction, and in particular as to whether 

 it utilized the principle of a vacuum created through 

 condensation of the steam. 



THOMAS SAVERY'S STEAM PUMP 



This principle was clearly grasped, however, by 

 another Englishman, Thomas Savery, a Cornish mine 

 captain, who in 1698 secured a patent for a steam engine 

 to be applied to the raising of water, etc. A working 



