642 
Latent Heat. 
[November, 
fall considerably below that of the earth before their heat 
emissions can be in equilibrium. The same rule, of course, 
applies to all spheres which exchange heat with each other, 
and thus a final equilibrium of heat exchanges could not be 
an equality of temperature in the orbs of space. 
Of the heat emitted by the sun only the 227 millionth 
part is caught by the planets, and this is nearly all yielded 
again to space. The vast remainder of the solar radiations 
flows out towards the remote spheres of the universe. Each 
of these receives but a minute fraction of this heat. Whether 
it shall be all eventually absorbed or reflected depends upon 
the improbable contingency that every possible straight line 
drawn outward from the sun shall somewhere meet a sun, 
a planet, or a smaller mass of condensed matter. It is the 
same with every other orb. Thus the heat radiated by the 
orbs into space can only in a minor sense be said to employ 
itself in producing temperature equilibrium between these 
orbs, since the great volume of it must wander unceasingly 
through space. Therefore space receives, in the radiant 
form, the excess temperature of the spheres, and is becom- 
ing, as it were, crowded with such ever-crossing rays. 
But is the transparency of the matter of space to radiant 
motion perfect ? May not its capacity for these rays be 
limited ? A good eledtric conductor will transmit feeble 
currents with little or no resistance, yet will strongly resist 
powerful currents, and partly convert the electricity into 
heat. The same rule may apply to radiations, which may 
become more and more converted into static or sensible heat 
as the current of heat-rays becomes stronger. Crossing, or 
reversely moving rays, or parallel rays in different phases of 
vibration, may also partly obliterate each other, and yield 
static heat vibration. It is possible, therefore, that radiant 
heat may slowly become converted into static heat in space, 
in which case temperature equilibrium between all matter 
may be slowly arising. If it ever be completely established, 
then the assumed original equilibrium of temperature, and 
of absolute heat in nebular matter, will be succeeded by a 
final equilibrium of temperature and an extreme diversity in 
absolute heat, the latent heat of the rare matter of space 
being immensely greater than that of the dense matter of 
the spheres. The absolute heat-contents, or motive energy, 
of a molecule at the centre of a dense sphere, must be 
greatly less than that of a molecule in interstellar space to 
give them the same temperature resistance, the one being 
vigorously aided in its resistance by its fellows, the other 
having to depend solely on its individual energy, and the one 
