.S7A' \\'ll.l. I.].M SIEMENS, F.R.S. 5 



cover I and drawing out the whole of the plates. An injection 

 K enters the condenser immediately below the plates ; it is 

 with a small air vessel L, and a regulating cock. Various 

 modes have been provided to give motion to the displacing piston 

 C, among which a knee motion worked directly from the beam or 

 crosshead of the engine is generally found the most convenient, as 

 shown at M M in Fig. 1. 



The action of the condenser is as follows. Motion is given to 

 the displacing piston C by the engine, causing it to accomplish two 

 strokes for every one of the engine. At the moment when the 

 exhaust port of the engine opens, the plates D are completely 

 immersed in water, a small portion of which has entered the 

 passage above the plates at A, and is, together with the air present, 

 carried off, by the rush of steam, through the valve G into the hot 

 well F, where the water remains, while the excess of steam escapes 

 at J into the atmosphere. An instant after the partial discharge 

 of the steam cylinder has commenced, the water recedes between 

 the plates D, and exposes them gradually to the steam, which 

 condenses on them in the manner following. The upper edges of 

 the plates, emerging first from the receding water, are enveloped 

 in steam. of atmospheric pressure, and in condensing a portion 

 thereof they become rapidly heated to nearly the temperature of 

 the steam, or about 210 Fahr. The partial condensation diminishes 

 the density and temperature of the remaining steam, which re- 

 quires additional and cooler surfaces for its further condensation. 

 This is provided for by the continual emerging of additional 

 portions of the metallic surfaces from the receding water. By 

 the time the water level leaves the bottom of the plates, the far 

 greater portion of the steam is condensed. The condensation of 

 the remaining portion of steam could not so readily be accom- 

 plished by means of metallic surfaces ; but the piston C, con- 

 tinuing to descend, causes it to come into immediate contact with 

 the jet of cold water from the pipe K, which completes the 

 vacuum in the manner of a common injection condenser. The 

 air vessel L, connected with the injection pipe, has the effect of 

 accumulating the injection water at the time when the water has 

 ascended between the plates, and of forcing it into the condenser 

 with increased intensity at the time when it is required to com- 

 plete the vacuum. 



