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the terrific quantity of heat so received and the terrific 
energy which this represents. We are taught that of the 
sun’s heat which heats on the earth one portion is refiected, 
another is absorbed, and that the latter is what we can 
alone recognize by our instruments, and whose energy is 
the subject of calculation. But the absorption of heat 
means, as we have argued, an increase of bulk, therefore 
whatever heat the earth absorbs must go to increase the 
earth’s size. It is only on this condition that the earth can 
absorb heat at all, and it is only by the increase in bulk 
that we can in fact measure or gauge the heat. 
But if the earth be shrinking it is clear that it must give 
out more heat than it absorbs, it must in fact produce 
enough heat to neutralize the expansion caused by the sun 
and some besides. The excess being measured by the 
amount of contraction that the earth is undergoing. But 
this means that any heat it receives from the sun is more 
than neutralized by its own heat, so that if the sun gave 
us no heat at all and the earth continued to contract, as it 
does now, it would not be affected in temperature, save 
perhaps in becoming even hotter, for if we receive heat 
from the sun which, when absorbed makes the earth ex- 
pand, it is clear that a portion of the contracting force of 
the earth is spent and exhausted in neutralizing this expan- 
sion, which would be set free in the form of heat if this had 
not to be neutralized. But I confess that having brought 
the argument to this point I am constrained to go a step 
further, and to say that if the earth be independent of the 
sun for its heat, that if independently of the sun altogether it 
is throwing out an amount of heat equivalent to the amount 
of its contraction, that it is unnecessary and unphilosophical 
to postulate the sun as a source of heat, and that we are 
bound, paradoxical as it may seem, to conclude that the 
earth does not receive any heat directly from the sun. This 
conclusion seems inevitable, and if it be, we must face the 
