56 THE SCIENTIFIC PAPERS OF 



ward) the piston of the regenerative cylinder remained com- 

 paratively quiescent upon its turning or dead point, and vice 

 versa. Around the two heating vessels boilers were disposed, 

 which received the heat of the fire, after it had acted upon the 

 former. The steam generated within the boilers was introduced 

 into the engine by means of an ordinary slide valve (of com- 

 paratively very small dimensions) at short intervals, and when 

 the piston of the regenerative cylinder was in its extreme posi- 

 tion. The admission of the steam, which was of high pressure, 

 took place on that side of the regenerative cylinder where 

 compression by the motion of its piston had already taken place, 

 and at the same instant a corresponding escape of expanded 

 steam on the other side of the regenerative piston was allowed to 

 take place into the atmosphere. The quantity of steam freshly 

 admitted at each stroke did, however, not exceed one-tenth part 

 of the steam contained in the working cylinders of the engine, 

 and served to renew the same by degrees, while it added its 

 own expansive force to the effect of the engine. The compres- 

 sion of the steam into either of the working cylinders took 

 place when its hollow piston stood at the bottom. While in 

 this position the steam occupied the annular chamber between 

 the working trunk and the cylinder, besides the narrow space 

 between the cylinder and the surrounding heating vessel. The 

 pressure of the steam being the same above and below the hollow 

 piston, but the effective area below being equal to twice the 

 area above, the working trunk, attached to the piston, would be 

 forced outward through the stuffing box, while the steam of the 

 annular chamber above the piston passed through the narrow 

 space intervening, into a space of twice the capacity of the 

 annular chamber below the hollow piston. During its passage 

 the steam had to traverse a mass of metallic wire gauze or 

 plates, the respirator, presenting a large aggregate surface, which 

 reached at one end sufficiently downward into the heating vessel 

 that its temperature was raised from 600 to 700 Fahr., while 

 its other extremity remained at the temperature of saturated 

 steam, or about 250 Fahr. In consequence of the addition of 

 temperature the steam received on its passage through the re- 

 spirator, its elastic force was doubled, and it therefore filled 

 the larger capacity below the hollow piston or displacer without 



