88i.] 
Latent Heat. 
591 
diffused gas, with a considerable degree of homogeneity, 
with a temperature largely equalised, and therefore with a 
considerable accordance in its absolute heat contents, what 
effects would condensation produce on its heat relations ? 
In considering the evolution of the solar system, scientists 
have attended principally to the physical aspects of the case, 
and but little to the force aspedfs. Physically we are pre- 
sented with two marked results. One of these is a continued 
condensation of the principal mass of the matter of the 
nebula, and its aggregation into dense globes. The other is 
a continued rarefaction of the remainder of the nebulous 
matter, ending in the production of an excessively rare and 
highly disintegrated interspheral matter. 
But such a process must have been accompanied by a 
great disturbance of the heat relations of this matter. As 
condensation continued, latent heat must have become sen- 
sible continuously, and the temperature of the contracting 
spheres must have greatly increased. And as rarefaction 
continued sensible heat must have become latent, and the 
temperature of the rarefying matter have considerably de- 
creased. Also, condensation must have been accompanied 
by continual chemical integration, and rarefaction by che- 
mical disintegration, thus considerably augmenting the above 
results. Thus the original partial homogeneity of tempera- 
ture may have become a great heterogeneity, without any 
necessary disturbance of the original equality of absolute 
heat contents. The difference in temperature would be 
caused simply by the latent heat of the contracting substance 
becoming largely sensible, and the sensible heat of the rare- 
fying substance becoming largely latent ; the one being, 
therefore, in ordinary language, greatly heated ; the other, 
greatly cooled. The final result has been, then, to replace 
the original partial equilibrium of temperature of the nebula 
by an extreme diversity of temperature between the matter 
of the spheres and of space, this great difference in temper- 
ature not, in itself, requiring any difference whatever in the 
absolute heat contents of these two conditions of matter. 
Two necessary consequences arose from this evolution of 
a solar system. One was a steady increase in temperature 
of the central sun, which was not probably balanced by its 
heat radiations. This increase may still continue, and may 
continue for ages to come, for the radiations of the sun may 
not equal its increase in temperature through condensation. 
It is quite possible, then, that the sun, instead of cooling off, 
is yet growing steadily hotter, the sensible heat yielded by 
compression only slowly reaching its surface and outflowing 
