506 On the two great powers, [Ocr. 
TI.—An Inquiry into the Laws governing the two great powers, Attraction 
and Repulsion, as operating in the Aggregation and Combination of 
Atoms. By Julius Jeffreys, Esq. 
; [Continued from page 464.] 
Moreover, there is another source for the sensible heat, in the 
sudden and forcible compression, which the circumjacent air under- 
goes, at the moment of the explosion, from which condensation the 
air itself must evolve heat. The explosion of euchlorine gas, with 
an evolution of heat, is perhaps a stronger objection, than the former, 
for it is not attended with a new combination of the elements. This 
is, however, an objection rather to one of the laws of heat, namely, its 
becoming latent, than to its materiality, against which, in fact, it is 
only an indirect objection, by shewing the law, that heat becomes 
latent in a change to a rarer state, not to be universal. But the whole 
doctrine of Jatent heat might be imperfect, and yet not invalidate the 
materiality of heat. Nor should an individual exception (supposing it 
to be such) be considered as subverting a doctrine of so perfect, and 
almost universal application, as is that of latent heat; much less then 
does it refute the material doctrine, which is not necessarily dependent 
on the former. 
The manner however, in which the above experiment is made, 
appears to me, as lessening greatly its force, as an exception to the 
doctrine of latent heat. A small quantity of the gas is used over 
mercury. As this liquid is incompressible, and so weighty as not to 
be readily susceptible of sudden motion, it must offer a very great 
resistance to the instantaneous expansion of the gas, and by this 
re-action may force out sufficient heat and light to become visible 
(i. e. a spark or flash) ; but after the expansion is finished, if much of 
the gas had been used, it is not improbable, that a fall of temperature 
would have been evident, in a thermometer introduced. 
4. The fact that some gases combine with each other, and form 
solids, with but a small rise of temperature, as when ammonia com- 
bines with many gases, is an objection the reverse of the former; and 
like it is an exception to the doctrine of latent heat. 
It may however be thus explained; that the affinity of such gases, 
both for heat, and for each other,” is so great, that it condenses most 
of their heat, without evolving it; in the same manner, as when 
oxygen and nitrogen gases are condensed in nitre. 
5. The contraction of clay by great heat, and of water in advancing 
from 32° to 40° of Fahrenheit, have been considered as objections to 
the law of expansion, and therefore to this doctrine of heat. The 
