AMERICAN 
JOURNAL OF SCIENCE AND ARTS. 
[SECOND SERIES.] 
Arr. XTI.—On the Elastic Force of Heated Air, considered 
asa Motive Power; by Frevericx A, P. Barnanp, 
sor of paategrcant i ai Natural History in me Uniseratyset 
‘Mabon 
In the d discussions which have recently taken place with regard 
to the power, economy and value of hot-air engines, the attention 
of all who have participated in them appears to have been exclu- 
sively directed to the advantages and disadvantages presented by 
a particular case. The question seems not to have been contem- 
plated in its more general aspect ; or rather it seems to have been 
assumed that there exists no general question which the success 
or failure of this particular experiment will not settle. Those 
who are satisfied that the engines of Capt. Eriesson cannot suc- 
ceed, seem ready at the same time to conclude that no engine 
whatever can be successful which proposes to derive its power 
from the same source. Experiment may prove this conclusion 
scientific history no in remarkable than true, that all those dis- 
tinguished men whose labors in this branch of science have illus-' 
trated the present age, and have built up the entire theory of ca- 
lorie as it is now received, have been completely in error in regard 
to one of their most important practical inferences, deduced ane 
the careful study of years et: 
Thompson, Rankine, Joule and. Regnault have ns 
the opinion that an air engine may be constructed w 
» Vol. XVII, No. 50.—. , 
