heat to be expected from the full moon." This however
is the amount of radiation measured by the Bolometer, and to get the
temperature of the radiating surface we must apply Stefan's law of the
4th power. Hence the temperature of the moon's dark surface will be the
[fourth root of (1 over 100)] = 1 over 3.2 [A] of the highest temperature
(which we may take at the freezing-point, 491 deg. F. abs.), or 154 deg. F. abs.,
just below the liquefaction point of air. This is about 50 deg. lower than the
amount found by calculation from our most rapid radiation; and as this
amount is produced in a few hours, it is not too much to expect that,
when continued for more than two weeks (the lunar night), it might reach
a temperature sufficient to liquefy hydrogen (60 deg. F. abs.), or perhaps
even below it.

[Note A: LaTex markup $\root 4 \of {1 \over 100} = {1 \over 3.2}$ ]

_Theory of the Moon's Origin._

This extremely rapid loss of heat by radiation, at first sight so
improbable as to be almost incredible, may perhaps be to some extent
explained by the physical constitution of the moon's surface, which,
from a theoretical point of view, does not appear to have received the
attention it deserves. It is clear that our satellite has been long
subjected to volcanic eruptions over its whole visible face, and these
have evidently been of an explosive nature, so as to build up the very
lofty cones and craters, as well as thousands of smaller ones, which,
owing to the absence of any degrading or denuding agencies, have
remained piled up as they were first formed.

This highly volcanic structure can, I think, be well explained by an
origin such as that attributed to it by Sir George Darwin, and which has
been so well described by Sir Robert Ball in his small volume, _Time and
Tide._ These astronomers adduce strong evidence that the earth once
rotated so rapidly that the equatorial protuberance was almost at the
point of separation from the planet as a ring. Before this occurred,
however, the tension was so great that one large portion of the
protuberance where it was weakest broke away, and began to move around
the earth at some considerable distance from it. As about 1/50 of the
bulk of the earth thus escaped, it must have consisted of a considerable
portion of the solid crust and a much larger quantity of the liquid or
semi-liquid interior, together with a proportionate amount of the gases
which we know formed, and still form,