6 THE SCIENTIFIC PAPERS OF 



Although the action of this condenser is strictly consecutive, 

 yet it does not check the continuous flow of steam from the 

 cylinder ; and it completes the vacuum when the working piston 

 of the engine has accomplished only one-tenth part of its stroke. 

 Both the engine crank and the crank driving the condenser are on 

 the top centre at the same moment, but the latter completes its 

 revolution in the time of half a revolution of the engine crank ; 

 consequently when the engine piston has passed through only one- 

 tenth of the whole stroke, the condenser crank will have travelled 

 through nearly half its stroke, by which time the whole process of 

 condensation will have been completed. 



The principal part of the latent beat of the steam is stored up 

 in the plates D, the upper extremities of which are heated to 

 210 Fahr., and the lower to about 150 Fahr. The water, in 

 ascending again between the plates during the last tenth part of 

 the engine's stroke, absorbs heat from them in a similar successive 

 manner, passing first the coolest and by degrees the hottest portions 

 of their surfaces ; and it issues finally into the upper steam passage A 

 at a temperature approaching the boiling point, at which moment 

 a fresh discharge of steam from the engine takes place, which 

 carries it off into the hot well, as above described, and raises its 

 temperature fully to the boiling point. 



Fig. 3, Plate 2, represents an actual indicator diagram, show- 

 ing the time occupied in completing the vacuum ; but it will be 

 observed that the loss of time and power may be diminished by 

 increasing the capacity of the displacing cylinder. As it is how- 

 ever, this loss does not amount to one-seventh part of a uniform 

 vacuum, an equivalent for which is obtained in the saving of the 

 power hitherto absorbed by the air pump ; for it will be observed 

 that the displacing piston works between two vacuums, and there- 

 fore meets with no resisting load. 



The quantity of condensing water required with this condenser 

 to condense 1 Ib. of steam of atmospheric pressure taking the 

 initial temperature of the condensing water at 60 Fahr., the final 

 temperature at 210 Fahr., and the latent heat of steam of 212 



Fahr. at 960 units is ^,-7^ - = 6*4 Ibs. of water to condense 

 ZiO bU 



1 Ib. of steam. The common injection condenser, supposing the 

 condensing and condensed water to issue at 110 Fahr., requires 



