590 
Latent Heat. 
[October, 
latent heat, or increasing or decreasing the absolute heat 
contents of fixed quantities of matter by rarefaction or com- 
pression, has a very important cosmical significance, as we 
shall proceed to show. 
The matter of space must, for two different reasons, pos- 
sess a much greater absolute heat than the matter of the 
spheres. It is, in the first place, excessively more rare than 
the atmospheres of suns and planets. But, as we have just 
seen, gases become cooled by rarefaction, or, in other words, 
their absolute heat for equal temperatures increases. In the 
second place, the matter of space is in a more disintegrated 
condition than that of the spheres, and perhaps, to a consi- 
derable extent, completely disintegrated. But chemical dis- 
integration also increases the latent heat contents of matter, 
or its absolute heat for equal temperatures. Thus the abso- 
lute heat of the matter of space must, for these two reasons, 
far exceed that of the matter of the spheres, if their tem- 
peratures be equal ; or, if their absolute heats approach 
equality, the temperature of interspheral matter must be 
greatly reduced below that of the spheres. 
Let us apply these conceptions to the case of the con- 
traction of a nebula from its original diffused condition to 
the final state of a solar system. Our own solar system, in 
its nebulous state, was an excessively diffused gas, its mate- 
rial much more homogeneous and disintegrated than at 
present. If we assume that this nebula was of equal tem- 
perature throughout, then its heat contents must have 
approached equality. Equal temperature now between 
spheral and interspheral matter would indicate a wide dif- 
ference in absolute heat contents, but in the matter of such 
a diffused and nearly homogeneous gas it would indicate but 
little difference. It is exceedingly improbable, therefore, 
that the matter of the primitive nebula was at a high tem- 
perature, or that it was a glowing gas, as so often assumed. 
Its high degree of latent or absolute heat could be only con- 
sistent with a low temperature, and very probably this tem- 
perature was considerably lower than the average of that of 
the earth’s surface at present, for its condition must have 
more nearly approached the present condition of interspheral 
than that of spheral matter. It was, in effeCt, a vast sponge, 
filled with heat, which heat has ever since been pouring out, 
as gravitation has squeezed the sponge into smaller dimen- 
sions. The original heat of the sponge was in great part 
latent. Compression has rendered it in great part sensible. 
Assuming, then, in the doCtrine of the nebular hypothesis, 
that the primitive state of the solar system was that of a 
