The Republican., 1895-08-22
THE ATMOSPHERE OF MARS.
Pfof. Campbell Declares There's Very
Little of 1t.


Pfof. Campbell Declares There's Very
Little of 1t.
mo observations of the planet Mars,
made while it was in an advantageous
position for study last summer and au-
tumn, excited quite as much interest
as those announced by Prof w. W.
campbell, of the Lick observatory staff.
The astronomers spectroscope scrutiny
led him to conclude that the ruddy orb
In question possessed less of an atmos-
phere than had previously been sup
posed; in fact, only about as much as
our moon has, which is generally sup
posed to be very little indeed. The re-
suits obtained by the Californian were
at variance with the findings of ex-
perts like Huggins, Seechi and Vogel,
to say nothing of younger and less
eminent authorities: and as soon as he
had told his story several of these as
tronomers made fresh Investigations,
which, though confessedly inadequate
owing to the lateness of the season,
seemed to corroborate their original
verdict. In the Astrophysical journal
Prof Campbell returns to the subject,
and his treatment of it is calculated to
inspire confidence in his accuracy.
Repeated comparison of the spectrum
OF the sun when that body is seen at a
low elevation land hence through
greater thickness of air. with that OBJ
tanned when it is much higher up, shows
4saat in the former situation there are
lines and bands which either disappear
or become much fainter in the latter
case. But certain other lines remain
equally strong. The latter, therefore,
are held to be true solar lines. while
the others are attributed to impurities
in the earths atmosphere. These are
called "telluric' lines and bands. A
planets spectrum is simply that of the
sun, with some trifing notifications,
inasmuch as it's light is not its own,
but is merely reflected sunlight. If
the planet has an extensive atmos-
phere with good deal of water in it,
this will introduce some additional
lines into its spectrum; but if it is al
most entirely devoid of such an en-
velope, like the moon, it will give back
spectrum like the suns; and any ad-
ditional lines perceived can probably
be identified as purely terrestrial
Now Prof. Campbell, in careful re-
view of all the best known spectre
scopic observations of Mars, shows that
the majority of them were made I'M
der unfavorable conditions, or give
very indistinct indications, or else
and this is his main point-were
affected by greater atmospheric hui
midity than his own We're. At
the expense of a good deal of
trouble, doubtless, he has obtained
data showing the moisture of the air
at the time and place of Huggins',
Maunder's and Vogel's latest observa-
tions. and shows that it greatly ex-
ceeded that on Mount Hamilton,
when he studied Mars himself. He
not only had the advantages of greater
altitude and superior spectroscope,
but he scrupulously selected nights
when the psychrometer indicated a
particularly dry air. His repeated fail
ure, under such circumstance, to find
the various bands and lines which the
foreign spectroscopists saw, or thought
they saw, suggests the proba bility
that these markings, if really per-
celved, were assignable to the aqueous
vapor in our own atmosphere Prof.
Campbell does not insist that the ques-
ton is settled. He graciously observes
that further study is requisite But he
makes out strong case. And if sub
sequent observation confirms the posi-.
tion he took last summer, his correc-
tion of scientific opinion about the ex-
tent of the atmosphere of Mars will re-
feet great credit upon him personally,
upon the institution with which he is
connected, and upon his country.-N.
Y. Tribune.