8O THE SCIENTIFIC PAPERS OF 



heated. This was shown in the experiment which had been men- 

 tioned, where the water was raised only 36 feet high in being 

 heated 26 ; but the perfect equivalent of heat as established 

 definitely by Joule's investigations and others subsequent, was 

 that the heat required to raise 1 Ib. of water 1 in temperature 

 would raise 1 Ib. a height of 772 feet, and 1 Ib. heated 26 would 

 raise 1 Ib. a height of 772 x 26 or 20,072 feet ; hence the economy 

 of the elevator was as 36 to 20,072, or only -^th of the theore- 

 tical perfect duty of the heat. A very good pumpiug-engine 

 realized th of the theoretical effect, and ordinary steam-engines 

 realized T \-th to T Vth, and were consequently 40 to 56 times 

 superior in duty to the elevator. The elevator was therefore 

 economically applicable only where fuel was no object, or as an 

 injector where the heat came in again usefully, as in feeding a 

 steam boiler. 



The injector, indeed, although inferior to a pump in mere 

 propelling power, he considered the most perfect instrument for 

 feeding boilers, so long as the supply-water was cool enough to 

 allow it to work ; for then all the heat imparted to the water 

 was returned into the boiler without any waste, whereas in 

 using steam to work a pump the larger part of the heat was 

 wasted by being thrown away with the exhaust steam. The in- 

 jector, however, would not be economical if the supply water could 

 be heated by other means free of expense, since its action required 

 the supply water to be kept cool. 



The amount of condensation in the long steam pipe mentioned 

 in the paper seemed small for such a length of pipe, and he thought 

 a good deal of water must be carried across the depositing box by 

 the current of steam and pass through into the elevator. He had 

 seen lately in France a simple and efficient contrivance by M. Le 

 Chatelier, for freeing the steam from water, by making the steam 

 pipe from the boiler descend vertically into the depositing box, 

 surrounded by a cylindrical and concentric casing, from the top of 

 which the steam was taken off for the engine ; the wet steam 

 rushing into the depositing box in a vertical current, carried for- 

 ward all the water it contained down to the bottom of the box by 

 the velocity imparted to it, while the steam itself turned sharp 

 round the bottom of the steam pipe and ascended through the 

 annular space, passing off dry, and the water was allowed to drain 



