Year: 1873

a
Shelley, that it seems strange to learn
from science that the full moon is so in
tensely hot that no creature known to us
could long endure contact with her heated
surface. Such is the latest news which
science has brought us respecting our
satellite The news is not altogether un-
expected; in fact, reasoning had shown,
long before the fact had been demonstrat-
ed, that it must be so. The astronomer
knows that the surface of the moon is
exposed during the long lunar day, last
ing q fortnight of our terrestrial time, to
the rays of a. sun as powerful, as that
which gives us our daily heat. Without
an atmosphere to temper the suns heat as, /;
ours does--not, indeed, by impeding the
passage of the solar rays, but by bearing
aloft the cloud-veil which the sun raises
from our oceans--the moons surface must
become intensely hot long before the mid
die of the lunar day. Undoubtedly the
want of an atmosphere causes the moons
heat to be rapidly radiated away into
space, 1t is our atmosphere which causes
a steady heat to prevail on our earth. And
at the SUBMITS of lofty mountains, where
the atmosphere is rare, although the mid,
day heat is intense, yet,so rapidly does the
heat pass away that snow crowns forever
the mountain heights. Yet although the I.
moons heat must pass away even more
rapidly, this does not prevent the heating
of the moons actual surface any more
than the rarity of the air prevents the I,
Alpine traveller from feeling the action of
the suns direct heat even when the air in
shadow is icily cold. Sir John Herschel
long since pointed out that the moons
surface must be heated at lunar midday
to a degree probably surprising the heat
of boiling water.


L., 80 at hparE
proved to be the case. The Earl of Rosse
has shown by experiments which need
not here be described that the moon not
only reflects heat to the earth (which, OF B
course, must be the case6 but that she
gives out heat by which she has been her
self warmed The distinction may not
perhaps appear clear at first sight to eve
ry reader, but il may easily be explained
and illustrated IT. on, bright tgsummers
day, we take piece of smooth but not TOO
we'll polished metal, and by means OF 1T
reflect the suns light upon the face, a SEN
sation of heat viii be experienced. This
is reflected sun-heat. But If we wait
while so holding the metal until the plate
has become quite hot under the solar rays,
we shall recognize a sensation of heat
from the mere proximity of the plate to
the face, even when the plate is so held as
not to reflect sun-heat. We can in sue
cession try-first, reflected heat alone, be-
fore the metal has grown hot; next, the
heat which the metal gives out of itself
when warmed by the SUMS rays; and
lastly, the two kinds of heat together ,
when the metal is caused to reflect sun
heat and also (being held near the facel
to give out sensible quantity Of its own
warmth. What Lord Rosse has done has
been to show that the full moon sends.
earthward both kinds of heat; she reflects
solar heat just as she reflects solar light,
and she also gives out the heat by which
her own surface has been warmed.


1t may perhaps occur to the reader to
inquire how much heat we actually OBJ
tain from the full moon. There is sim
pie way of viewing the matter. If the
full moon were exactly as hot as boiling
water, we should receive from her just as
much heat Qeaving the effect of our at
mosphere out of account as we should re-
ceive from small globe as hot as boiling
water, and at such distance as to look
Just as large as the moon does. Or disk
of metal would serve equally well. The
experiment may be easily tried. An old
fashioned penny is just one inch in DIAM
eter, and as the moons average distance
! is about III times her own diameter,
penny-at distance of Ill inches, or three
yards and three inches, locks Just as large
as the moop... Now let penny be put in
boiling water for while, so that 1t be-
comes as hot as the water; then that coin,
taken quickly and set three yards from
the observer, will give out for the few mo-
ments that its heat remains appreciably
that of boiling water, so much heat to the
observer as he receives from the full moon
supposed to be as hot as boiling water,
Or globe of thin metal, one inch in di-
ameter, and full of water at boiling heat,
| would serve as more constant artificial
moon in respect of heat-supply. 1t need
not be thought remarkable, then, If the
heat given out by the full moon is not
easily measured, or even recognized. I'M
agine how little the cold of a winters day
would be relieved by the presence in
room not otherwise warmed OF one-lnch
globe of boiling water three yards away!
And, by the way, we are here reminded OF
an estimate by Professor G. p. Smyth, re-
sulting from observations made on the
moons heat during his Teneriffe expert
ments. He found the heat equal to that
emitted by the hand at a distance of three
| feet.


But, after all, the most interesting re-


suits flowing from the recent researches


are those which relate to, the moon her
self We cannot but speculate on the
condition of world so strangely circum-


stanced that cold more bitter than that
of our Arctic nights alternates with heat


exceeding that of boiling water. 1t is


strange to think that the calmlooking


moon is exposed to such extraordinary
vicissitudes. There can scarcely be life


in any part of the moon-unless it be un-
er-ground life, like that of the Modoc


Indians 1--WE commend this idea specially


to the more ardent advocates of Brew


sterian ideas respecting other worlds than


ours). And yet there mast be singular


ly active mechanical progress at work in


yonder orb, The moons substance must


expand and contract marvelQusly as the


alternate waves of heat and cold pass over


it. The material of that crater covered


surface must be positively crumbling


away under the effects of these expansions


and contractions. The most plastic ter


restial substances could not long endure


such processes, and IL seems altogether


unlikely that any part of the moons crust
is at all plastic. Can we wonder II IRON


time to time astronomers tell US of appar-


ent changes in the mOon-a wall sinking


here, or crater vanishing elsewhere?


The wonder rather is that the steep and


lofty lunar mountains have net been


shaken long since to their very founda-


tiOns. -F-as r.


Our moon presents, in fact, strange


problem for our investigation. 1t is graft


flying to our terrestrials to regard her rs a
mere satellite of the earth, but in reality


she deserves rather to be regarded as q
companion planet She follows a path
round the sun which so nearly resembles


that pursued by the earth, in shape as we'll
as in extent, that if the two paths were
traced down on quarto sheet it would
not be easy to distinguish one from the
other Our earth is simply the largest,
while the moon is the smallest of that
inner family of worlds over which the
sun bears special sway, nor does Mercury


exceed the moon to so great degree IN
[ mass and in volume as the earth or Venus
exceeds Mercury Yet the moon, with her


surface of fourteen million square miles,
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