32 PROCEEDINGS OF THE AMERICAN ACADEMY 



seven miles an hour, which, compared with the speed of the 

 CoUins steamers, would make the Ericsson consume twenty- 

 five per cent, more fuel than the latter. 



At the former meeting he had not considered the " cut-ofF," 

 which gives a result more in favor of the Ericsson ; thongh 

 this advantage is compensated by the error he made in favor 

 of the Ericsson engine by taking the heat of the cylinders 

 at 480'^, whereas the actual heat used was only 384°. The 

 '' cut-ofF" may be so short that the regenerator would be use- 

 less, the air going in and out at the same temperature, though 

 more fuel would be required in this way. The shorter the 

 "cut-off," the greater would be the theoretical power, provided 

 you could get the air in. The "cut-off" in this engine is at 

 three fourths of the stroke ; for one fourth of the stroke there 

 would be a pressure of three fifths above an atmosphere, and 

 for the other three fourths of the stroke only one fifth above 

 an atmosphere. One pound pressure would be required to 

 force the air out through the wire-gauze, instead of the half- 

 pound previously mentioned ; and one and one fifth pounds 

 pressure to force it in. 



Dr. W. F. Channing remarked, that the difference in the loss 

 of power from paddles entering the water (which is great in 

 steam-vessels), and the less amount of friction, give more 

 power to this engine. He thought, that, deducting one pound 

 pressure (necessary to force the air through the wire-gauze) in 

 place of half a pound allowed by Professor Peirce, there is a 

 pressure of only one fourth of a pound left ; and deducting 

 from this 40 horse-power (equivalent to two fifths of a pound 

 pressure, by Professor Peirce's calculation) for the loss from the 

 paddles entering the water, and one fifth of a pound of pres- 

 sure for additional friction, there would be a pressure of minus 

 seven twentieths of a pound to an inch inside the cylinder, 

 or, in other words, that the engine was worked by an outside 

 atmospheric pressure acting inwards. 



Professor Josiali Parsons Cooke and Professor Joel Parker 

 of Cambridge were elected Fellows of the Academy ; the 



