OF ARTS AND SCIENCES. 29 



In the first place, he showed that this engine does not use 

 the heat over and over again, and that when the air in the 

 cylinders becomes expanded, in other words, whenever work 

 is done (for no work is done while the piston is descending), 

 heat is lost irrecoverably, and can only be resnpplied by more 

 fuel. 



In the second place, he showed that, with the same amount 

 of fuel, not so much work was done, nor was it so well done, 

 as by steam. Still it was an exceedingly ingenious and well- 

 perfected method of using hot air as a motive power, and in 

 certain cases may become quite a rival of the steam-engine. 



He gave a minute description of the different parts of the 

 engine, illustrated by diagrams. In the large cylinder, the 

 pressure never exceeds five pounds to the square inch, and 

 never can, unless the heat be raised above 550^, which is the 

 maximum temperature said to be used in Ericsson's engine ; 

 to get fifteen pounds to the square inch, he must heat his 

 cylinder to 1000'^, or to a red heat. Professor Peirce used 

 480'^ in his calculations. 



This engine has four cylinders, nine strokes a minute, six 

 feet to a stroke, and one hundred and fifty square feet of piston ; 

 it is said to consume only six tons of coal a day. Mr. Peirce 

 calculated the working power of the engine to be only 116 

 horse-power; he compared this with the Baltic steam-ships 

 with 2314 horse-power, twenty times the power of Ericsson's 

 engine. To raise the Ericsson to the Baltic's power, one 

 hundred and twenty tons of coal a day would be demanded, 

 while the Baltic uses only eighty ; so that the economy of 

 fuel, one of the great advantages ascribed to the Ericsson, is 

 in reality in favor of steam-vessels. The power of the Erics- 

 son would be nothing against a head sea, and her speed of 

 eight miles an hour on her trial trip is less than steam-vessels 

 of inferior model made ten years ago. As yet the Ericsson 

 engine has not only not surpassed steam-vessels, but has not 

 even equalled them. 



As to the alleged saving of heat, the Ericsson loses 60° of 



