232 Mr. C. W. Siemens, on a- [April 11, 



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 comparatively very small dimensions) at 

 short intervals, and when the piston of the regenerative cylinder 

 was in its extreme position. 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 compression 

 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 

 so that its temperature was raised from 600 to 700° Fah., while its 

 other extremity remained at the temperature of saturated steam, or 

 about 250° Fah. In consequence of the addition of temperature 

 the steam received on its passage through the respirator, its elastic 

 force was doubled, and it therefore filled the larger capacity 

 below the hollow piston or displacer without loss of pressure. When 

 the effective stroke of the working trunk was nearly completed, the 

 regenerative piston commenced to recede, and the steam below the 

 hollow piston expanded into the regenerative cylinder, depositing 

 on its regress through the respirator the heat it had received on its 

 egress through the same, less only the quantity that had been lost 

 in its expansion below the working piston, and which was converted 

 into dynamic effect or engine power, and which had to be supplied 

 by the fire. The expansion and simultaneous reduction of tempe- 

 rature of the steam caused a diminution of its pressure from four 

 to nearly one atmosphere ; and the working trunk could now effect 

 its return stroke without opposing pressure, and while the second 

 working trunk made its effective or outward stroke impelled by a 

 pressure of four atmospheres. 



