Year: 1873

ing to the image used alike by WORDS
worth and Shelley, that it seems
strange to learn from science that the
full moon is so intensely 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 unexpected in
fact, reasoning had shown, long before
the fact had been demonstrated, that it
must be so. The astronomer knows
that the surface of the moon is exposed
during the long lunar day, lasting a
fortnight of our terres trial time, to the
rays of the sun as powerful as that
which gives us our daily heat. With
out an atmosphere to temper the suns
heat as ours does, not, indeed, by i'm
peding the passage of the solar rays,
but by bearing aloft the cloud-veil
which the sun riases from our oceans
the moons surface must become in
tenseIy hot long before the middle of
the luner day. Undoubtedly the want
of an atmosphere causes the moons
heat to be rapidly radiated away into
space. It 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 midday heat is in
tense, yet so rapidly does heat pass
away that snow crowns forever the
mountain heights. Yet although the
moons heat must pass away even more
rapidly, this does not prevent the heat
ing of the moons actual surface any
more than the rarity of the air prevents
the Alpine traveller from feeling the ac-
ton of the suns direct heat even when
the air in shadow is icily cold. Sir
John Herschel long since pointed ont
that the moons surface must be heated
at lunar mid day to a degree probably
surprising the heat of boiling water.


Such, in point of fact, has now been
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
course. must be the case), but she gives
out heat by which she has been herself
warmed. The distinction may not per-
haps appear clear at first sight to every
reader, but it may easily be explained
and illustrated. If, on a bright sum-
mer's day, we take a piece of smooth
but not too we'll polished metal, and by
means of it reflect the suns light upon
the face, a sensation of heat will be ex-
perienced. 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 re-
cognize a sensation of heat fIom the
mere proximity of the plate to the face,
even when the plate is so held as not to
- Iao INa IN o1aanCcInn
trv. first. reflected heat alone, before
the metal has grown hot next, the heat
which the metal gives out of itself when
warmed by the suns rays and lastly,
the two kinds of heat together, when
the metal is caused to reflect sun-heat,
and also Cbeing held near the face) to
give out a 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 hea just as she reflects
solar light, and she also gives out the
heat by which her own surface has been
warmed.


It may perhaps occur to the reader to
induire how much heat we actually OBJ
tain from the full moon. There is a
simple way of viewing the matter. If
the full moon were exactly as hot as
boiling water, we should receive from
her lust as much heat Qeaving the eff
feet of our atmosphtre out of account)
as we should receive from a small globe
as hot as boiling water, and at such a
distance as to look just as large as the
moon does. Or a disk of metal will
serve equally well. The experiment
may be easily tried. An oldfashioned
penny is Just one. inch in diameter, and
as the moons average distance is about
III times her OWE diameter, penny at
a distance of Ill inches, or three yards
and three inches, looks just as large as
the moon. Now let penny be put IN
boiling water for while, so that it 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 moments that it's heat remains ap-
preciably 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 a globe of
thin metal, one inch In diameter, and
full of water at boiling heat, would
serve as O 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.
Imagine how little the cold of a winters
day would be relieved by the presence
in room no otherwise warmed of one
inch globe of boiling water three yards
away! And, by-the-way, we are here
reminded of an estimate of @. P. Smyth,
resulting from observations made on
the moons heat during his Teneriffe
experiments. He found the heat equal
to that emitted by the hand at a dis
tance of three feet.


But. after all, the most interesting
results flowing from the recent re-
searches are those which relate to the
moon herself We cannot but specu-
late on the condition of world SO
strangely circumstanced 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 calm-looking moon is ex-
posed to such extraordinary vicissitudes.
There can scarcely be life in any part Of
the moon, unless it be underground
life. like that of the Modoc Indians 1--WE
commend this idea specially to the more
ardent advocates of BreTsterian ideas
respecting other worlds than ours)'
And vet there must be, singularly ac-
tive mechanical progress at work in yon-
der orb. The moons substance must
expand and contract marvelously 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 terrestrial substances could
not long endure such processes, and it
seems altogether unlikely that any part


of the moons crust is at all plastic. Can


we wonder if from time to time astrono-


mers tell us of apparant changes In the


moon, a wall sinking here, or crater


vanishing elsewhere The wonder


rather is that the steep and lofty luna


mountains have not been shaken long


aimee to their very foundations.


Our moon presents, in fact, a strange


problem for our investigation. 1t is


gratifying to us terrestrials to regard


her as a mere satellite of the earth, but


in reality she deserves rather to be re-


garded as companion planet.