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; Ill
fact, reasoning had shown, long before
the fact had been demonstrated, that 1t
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
tensely hot long before the middle OF
the luner day. Undoubtedly the want
of an atmosphere causes the moon S
heat to be rapidly radiated away into
space. 1t is our atmosphere which
causes a steady heat to prevail on onr
earth. And at the SUBMITS of lofty
mountains, where the atmosphere is
rare. although the midday heat is in
tense. vet 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 c)ld. Sir
John Herschel long since pointed out
that the moons surface must be heated
at lunar mid day to 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
aud illustrated. If, on a bright sum-
mer's day, we take 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 snn-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 ftOm 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 succession
try. 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 (being held near the face) to
give ont 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 rs she reflects
solar light, and she also gives out the
heat by which her own surface has been
warmed.


It NAV perhaps occur to the reader to
inUuire how much heat we actually OBJ
tain from the full moon. There is a
simple way of viewing the matter. Ii
the full moon were exactly as hot as
boiling water, we should receive from
her Just as much heat Qeavlng the Ell
feet of our atmosphtre out OF account,
as we should receive from small globe
as hot as boiling water, and at such
distance as to look just as large as the
moon does. Or a disk of metal will
serve equally we'll. The experiment
NAV be easily tried. An oldfashioned
penny is inst one inch in diameter, and
as the moons average distance Is about
III times her own diameter, a penny al
a distance of III inches, or three yards
and three inches, looks just as large a.
the moon. Now let penny be put II
boiling water for a while, 30 that 1T be
comes as hot as the water; then tha
coin taken quickly and set three yards
from the observer, will give out for th'
few moments that its heat remains ap
preciably that of boiling water so mucl
heat to the observer as he rec, i've
from the full moon supposed to be a
hot as boiling water. Or globe o
thin metal, one inch in diameter, an(
full of water at boiling heat, woul,
serve as a m ore constant artificial mool
in respect of heat supply. 1t need no
be thought remarkable, then, if tn


heat given out by the full moon is no
easily measured, or even recognized
Imagine how little the cold of a winter
day would be relieved by the presenc


in a room no otherwise warmed of a one
inch globe of boiling water three yard


away! And, by-the-way, we are her


reminded of an estimate of G. P. Smyth


resulting from observations made o.


the moons heat during his Teneriff


experiments. He found the heat equa
to that emitted by the hand at dis


tance of three feet.


But, after all, the most interesting


results flowing from the recent re
searches are those which relate to tn


moon herself. We cannot but specu


late on the condition of a world s


strangely circumstanced that col


more bitter than that of our Arcti


nights alternates with heat exceedin


that of boiling water. 1t is strange t


think that the calm-looking moon is ez


posed to such extraordinary vicissltudes


There can scarcely be life in any part G


the moon, unless it be under-groun


life. like that of the MOdOc Indians Nv


commend this idea specially to the NOR


ardent advocates of Bre ! sterian idea


respecting other worlds than ours


And yet there must be singularly ~


tive mechanical progress at work in yol