On the Expenditure of Heat in the Hot-air Engine. 219 
0 
whether justly or not, the present writer, having met with noth- 
ing on the subject published with his explicit sanction, is unable 
to say.* Whatever may be his own views, however, reporters 
who have heard him and friends who speak for him, have so ex- 
pressed themselves, as to leave no doubt that they so understand 
him. 'To such persons a curious practical paradox may be pro- 
posed, for which they wguld find it difficult to account, as follows : 
Suppose an engine to be constructed on Ericsson’s plan; but 
? 
* Since this was written, an article by Capt. Ericsson, published in Appleton’s 
Mechanics’ ine for June, has come sdivden the eye of the writer. It leaves 
no doubt that Capt. Ericsson’s views have been correctly represented in the a 
tions which have heretofore been made, on his behalf, though not avowedly by bis 
authority, 
t It 2 usual to put 1= density at 32°, under pressure of 30 inches of mercury. 
For our present purposes, it is convenient to make the density at 60° = unity, 
modifying the co-efficient of expansion, as explained further on. 
