30 PROCEEDINGS OF THE AMERICAN ACADEMY 



heat at each stroke, which must be made up ; the maximum 

 heat ill the wire-gauze apparatus is 30^ below the heat iu 

 the cylinders ; all the air iu the cylinders must have sup- 

 plied to it 60^ of heat. At least one half a pound pressure 

 to the inch, and probably much more, is required to force 

 the air through the wire-gauze. 



Dr. Bowditch alluded to the instrument called the " respira- 

 tor," as analogous in its action to the wire-gauze in Ericsson's 

 engine, iu which the heat is often so retained as to be uncom- 

 fortable to the patient. 



Professor Peirce observed that this apparatus of Ericsson 

 was undoubtedly of great value for the working of his engine. 



Professor Tread well remarked that this same analogy to the 

 " respirator " had been brought forward in 1847 in regard to 

 Stirling's engine, which had an advantage over Ericsson's in 

 using the same air over and over again. Air has an advantage 

 of one half or two thirds over steam in the matter of specific 

 heat, and if it could be used as conveniently without forcing- 

 pumps, &c., it would be far superior as a motive power; but 

 as yet the chief obstacles have not been removed. 



Dr. W. F. Channing observed that Professor Peirce, in his 

 calculations, had used the power necessary to double the speed 

 in a given time as the cube, whereas, in the published accounts, 

 it had been given as the square; and that thus so little power 

 had been left (about | lb. working power to the inch), that it 

 seemed quite providential that the vessel had moved at all. 

 To which it was replied, that when the element "space " is 

 taken in the formula instead of " time," the square becomes 

 doubled, or the cube. 



Three bundred and seventy-fifth meeting. 



February 1, 1853. — Adjourned (Quarterly Meeting. 



The President in the chair. 



Professor Levering reported that the map of the tornado at 

 Medford was engraved, and that the report, by Professor 



