504 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



double acting. The other one is used as a supply cylinder, and 

 for transferring the air at the proper time to the heater. Thia 

 cylinder is double acting. The pistons in these two cylinders 

 are connected to two cranks placed at nearly right angles. The 

 action of the cranks gives the piston a differential movement, 

 approximating that which theory would indicate. The smooth- 

 ness of motion due to the action of the crank, in practice com- 

 pensates for the want of theoretical accuracy. Between these 

 two cylinders is another chamber, connecting both at the bottom, 

 and containing the economizer, composed of metal plates so 

 placed as to permit the free passage of the air between them. 

 The economizer is equivalent in construction and effect to the 

 "regenerator" of Stirling and Ericsson. The practical effect of 

 the economizer has been disputed, but experiments with thia 

 engine indicate that there is a practical economy in its use. This 

 engine has been found to run at twice the speed, other things 

 being equal, with as without the economizer. It is also found 

 that the effect of the economizer in causing a difference of tem- 

 perature in the same air, passed repeatedly through it, will cause 

 the engine to run half an hour or more, without taking in a fresh 

 supply of air. Over the economizer is a single rolling valve per- 

 forming the threefold office of induction, eduction and equilibrium 

 valve. The bottoms of both cylinders and the economizer cham- 

 ber are used as a heating surface, the fire being so placed that 

 the products of combustion circulate, first, underneath, and then 

 around the sides of the cylinder before reaching the smoke-flue. 

 The heaters are protected from the intense action of the fire at 

 any one point. It has been found in "these engines, and also in 

 the Stirling, that a better effect is obtained from the same amount 

 of fuel by this arrangement of flues than when the fire is allowed 

 to act directly upon the heater, while it is evident that the heaters 

 will endure longer in consequence of being exposed to a more 

 equable temperature. If any one part is overheated it will cause, 

 by its expansion, a strain which tends to weaken and destroy the 

 whole. He thought the Wilcox engine heated the air to as high 

 a degree as the Ericsson, with a lower temperature in the heaters, 

 owing to the large extent of the heating surface. To prevent 

 overheating any part while the engine is stationary, Mr. Wilcox 

 has devised a self acting regulator which closes the damper, or 

 opens a passage way for cold air over the fire in case the heaters 

 are raised above a safe temperature. He then described the 



