254 M. Arago's Biographical Memoir of James Watt. 



tube properly placed, and forces it downwards, as did the 

 atmosphere in the machine of Newcomen. This movement 

 meets with no obstacle, provided that, during the period of its 

 execution, the lower part of the cylinder alone be in commu- 

 nication with the condenser, whither all the lower steam rushes 

 and is liquefied. So soon as the piston has quite descended, 

 the simple turning of a stopcock, makes the two parts of the 

 cylinder situated above and below the piston communicate,* — 

 these two spaces are filled with steam of the same degree of 

 elasticity, the piston is then put in equilibrium, and reascends 

 to the top of the cylinder, as in Newcomen's atmospheric lua- 

 chine, by the mere action of a counterpoise. 



In prosecuting his researches as to the means of economiz- 

 ing steam. Watt reduced almost to nothing, the loss which 

 resulted from the cooling down of the outside of the cylinder 

 in which the piston played. For effecting this object, he en- 

 closed the metallic cylinder in a wooden one somewhat larger, 

 and filled the space between them with steam. 



Thus, then, was the steam-engine completed. The improve- 

 ments it received from Watt are evident, and of their im- 

 mense utility, there cannot be a doubt. You will, therefore, an- 

 ticipate, that it would immediately displace, as a draining appa- 

 ratus, the comparatively ruinous machines of Newcomen. This, 

 however, was far from being the case. The author of a disco- 

 vi'ry has always to contend with those whose interests may be 

 afi'ected, with the obstinate partisans of whatever is ancient, 

 an I finally, with those who are jealous, — and these three classes 

 urited form (must we confess it ?) the great majority of the pub- 

 lic. Yet, to avoid a paradoxical result, I leave out of my calcu- 

 lation all those who had double motives. It is time alone that 

 can disunite and scatter this phalanx of opponents. Nor will 

 time alone do it. They must be energetically and unceasingly 

 attacked ; and the means used must be varied, as is done by 

 the chemist whom experience has taught that the complete so- 

 lution of certain compounds requires the successive employ- 

 ment of several acids. The strength of character and firm- 



* The communication with the condenser must at the same time be cut 

 off.— Ed. 



