New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1895-07-15
SCIENCE AND MECHANICS
THE ATMOSPHERE OF MARS.
From The Weekly Tribune.
PROFESSOR CAMPBELL BACKS UP HIS FORMER


PROFESSOR CAMPBELL BACKS UP HIS FohMH"
STATEMENT THAT THERE'S VERY
LITTLE OF IT.
M observations OF the planet Mars. made while "
was In an advantag eous position for study LAST SUM
ucar and autumn excited quite 80 much Interest as
,bos. announced by Professor w. w. Campbell, OF INC
Lick Observatory staff. That astronomer specio
scopc scrutiny led him to ccHclrde that inc ru'''
orb in question possessed less OF an aifnosp"e,.
than had previously been supposed: In fact' o"'
about as much as moon has. which IS gem
orally believed to be very little indeed The re-
suits obtained by the Californian we're at variance
with the findings OF veteran experts ike huss",
Sccchi and Voge to say nothing OF youhee. az,
lers eminent authorities; and as soon az ne hao '
his story several Of these astronomers maze He'"
invostiations which, thouh ccrfessedly Inadequate
owing to the latencss of the season. seemed ~ co'
roborate their original verdict In the latest Issue
of THE Astrophysical Journal Professor campoe''
returns TO the subject. and his treatment Oh II 70
calculated to inspire confidence In hs accuracy
Repeated comparison Of the spectrum OF the 81"
when that body Is a; low elevation (and hence
through a greater thickness OF air. with tnat oo
tanned when 1t is much higher up. shows that III .he
former situation there are lines and bands WHICH
either disappear become much fainter IN the 'a'
ter case. But certain other lines remain equahS
strong. The latter. therefore, are held to De true
solar lines while the others attributed to mpur'
"teuric" lines and bands. planets spectrum
is simply that OF the sun, with some trlhns moo'i-
cations inasmuch Its light is not its own, but Is
merely reflected sunlight II the planet has an
extensive atmosphere, with god deal OF wa'e'
vapor In IT, this will introduce some additional lines
into It's spectrum but II 1t Is almost entirely deVo
of such an envelop like the MOON II will give bacK
a spectrum like the suns; and any additional bhes
perceiyed can probably be identified purely ter
restriaI Now Professor Campbell. in a careful re-
view OF all the best known spectroscopIc observa-
lions OF Mars shows that the majority Of them were
made under unfavorablc conditions or gave very IN
distinct indications. or ese-and this Is his main
pont-were affected by greater atmospheric humid
ity than his At the expense. OF n good
deal OF trouble doubtless. ne has obtained data
showing the moisture Of the air at the time ana
place OF Huggins's Maunder's and Vogels latest oo-
seryations and shows that II greatly exceeded that
on Mount Hamilton. when he studied Mars himself
He not only had The advantages OF greater altitude
and superior spectroscope. but he scrupulously Sc
lected nights when the psychrome;er indicated
particularly dry air. His repeated failure. under
such circumstances. to find the various bands ana
lines which the foreign spectroscopsts saw OF
thought they saw. suggests the probability tha'
those markings. II really perceived. were asslgna-
bic to the aqueous vapor in our own atmosphere
Professor Campbell does not insist that the question
study is requisite. But ne makes out strong case
And II subsequent observation confirms the position
ne took last summer his correction OF sclentinr
opinion about the extent OF the atmosphere OF Mars
the institution with which he Is connected. and upon
his country