218 On the Expenditure of Heat in the Hot-air Engine. 
tallized serpentines or of interstratified masses of this mineral, as 
far as 1 am aware, have there been observed any marks of the 
disruption, displacement, and other mechanical effects which 
should result from such a great increase in volume. 
he advocates of this hypothesis as to the origin of serpentine, 
will scarcely maintain that the action in this case is different 
from that which should produce aspasiolite from iolite, or im- 
agine a removal of both silica and magnesia from part of acrys- 
tal of chrysolite, while the surrounding silicates and carbonate of 
magnesia are like the remainder of the crystal, unaltered. The 
generally admitted notions of pseudomorphism seem to have 
originated in a too exclusive plutonism, and require such varied 
hypotheses to explain the different cases, that we are led to search 
for some more simple explanation, and to find it in many instan- 
ces, in the association and erystallizing together of homologous 
and isomorphous species : 
We have in these pages given the first series of illustrations 
of our views respecting the homologies of chemical formulas, 
and the similarity of volume in isomorphous species; it is be- 
lieved that these views will be found to enlarge and simplify the 
plan of chemical science, and lead to a correct mineralogical 
system. 
Montreal, Canada, June 21st, 1853. 
Arr. XXIII.— Theoretic Determination of the Expenditure of 
Heat in the Hot-air Engine; by F. A. P. Barnarn, Professor 
ee Chemistry and Natural History, in the University of Ala- 
ama. 
the time, all the heat which has ean imparted to it during the 
expansion. {t would follow as a corollary, that, if such air could 
