THE STEAM-ENGINE. 113 



actual use his water-raising engine. We have a model of 

 that engine here. It comprised the steam-boiler connected 

 "by a pipe (controlled by a cock) with the water-vessel. Steam 

 being admitted and then shut oif, a water-cock was opened, 

 which allowed a cold jet of water to play over the outside of 

 the water-vessel, condensing the steam and making a partial 

 vacuum within the vessel, and thereby enabling it to " suck 

 up " (to use a most convenient but unscientific term) the 

 water from the source of supply ; which water, being retained 

 by a suction-valve, was on the next admission of steam 

 forced through the delivery-valve to the desired elevation, 

 the difference between Savery and Papin being that Savery 

 made use of exhaustion to do part of the raising, and that he 

 did not have a floating diaphragm between the steam and the 

 water to diminish the amount of steam lost by condensation. 

 The engine of Savery was put to work and used to a con- 

 siderable extent, notably at the waterworks, York Buildings, 

 in London, which were situated where Charing Cross Station 

 now is. 



As I have said, Savery's engine did not remain in the 

 region of idea, nor even in that of mere experiment, but 

 it was put to work in several places, and was thus fully 

 tested. These testings, while they showed the merits, showed 

 also the defects of Savery's invention, and these defects were 

 of special importance in days when leaden pipes and plumbers' 

 joints had to be relied on to resist high pressure of steam ; for 

 you will see that in a water-raising engine such as this (as 

 also in the engine of Papin) the steam acting directly upon 

 the surface of the water to be raised must press with a 

 force per square inch equal to the balancing and to the 

 setting into motion (against the resistance of friction as well 

 as that of gravity) of the water to be lifted, and that thus to 

 raise water, say 115 feet, would demand (friction apart) a 

 steam-pressure of 501bs. above atmosphere, or probably, allow- 

 ing for the friction and the loss by condensation, GOlbs. or 

 more in the steam generator. 



With an apparatus such as this, therefore, no alteration 

 either of dimensions or proportions could enable you to evade 

 the fact, that the steam pressure per square inch must be 

 sufficient, not only to balance the column of water, but also 

 sufficient to overcome the friction and all other resistances. 

 Under these circumstances, it is by no means surprising that 



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