of the lunar rocks would
have to be raised above the absolute zero (-273 deg. C. or -459 deg. F.) in
order that they might throw off into space as much heat in a second as
they would get from the sun in a second. But Professor Langley's
observations, made on Mount Whitney at an elevation of fifteen
thousand feet, when the barometer stood at seventeen inches
(indicating that about fifty-seven per cent. of the air was still
above him), showed that rocks exposed to the perpendicular rays of the
sun were not heated to any such extent as those at the base of the
mountain similarly exposed; and the difference was so great as to make
it almost certain that a mass of rock not covered by a reasonably
dense atmosphere could never attain a temperature of even 200 deg. or 300 deg.
F. under solar radiation, however long continued.

It must, in fact, be considered at present extremely doubtful whether
any portion of the moon's surface ever reaches a temperature as high
as -100 deg..

The subject, undoubtedly, needs further investigation, and it is now
receiving it. Professor Langley is at work upon it with new and
specially constructed apparatus, including a "bolometer" so sensitive
that, whereas previous experimenters have thought themselves fortunate
if they could get deflections of ten or twelve galvanometric divisions
to work with, he easily obtains three or four hundred. We have no time
or space here to describe Professor Langley's "bolometer;" it must
suffice to say that it seems to stand to the thermopile much as that
does to the thermometer. There is good reason to believe that its
inventor will be able to advance our knowledge of the subject by a
long and important step; and it is no breach of confidence to add that
so far, although the research is not near completion yet, everything
seems to confirm the belief that the radiated heat of the moon,
instead of forming the principal part of the heat we get from her, is
relatively almost insignificant, and that the lunar surface now never
experiences a _thaw_ under any circumstances.

Since the superstition as to the moon's influence upon the wind and
weather is so widespread and deep seated, a word on that subject may
be in order. In the first place, since the total heat received from
the moon, even according to the highest determination (that of Smyth),
is not so much as 0.00001 of that received from the sun, and since the
only hold the moon has on the earth's weather is th