New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1881-07-18
THE COMETS light POLIRIZED.

LETTER FROM PROFESSOR A w. WRIGHT
RESULTS OF EXPERIMENTS WITH THE PoI.>R1scopE
AND NEUTRALITY-SUSPICIOUS. FACTS DEDUCED
FROM OBSERVATIONS Oh THE COMET OF 1881.
To the Editor OF Thc Trfbunc
SIR; Observations made 10y me havo resulted in
establishing the fact that the light emitted by the
tan of the comet il polarzed rather strongly in n
plane passing through the suns place The exist
ence of the polarization was satisfactorily proved
with the ordinary polariscopic apparatus though
owing to the moderate intensity of the light the OBJ
servation made with great difficulty A nodih-
cation of the poarmeter used in the observation Of
the solar corona in the eclipse of July 20, ISIS
made IT possible NOT only to fix the direction of the
polarization, but even to measure its amount Tho
condition of the sky too unfavorabe during the
first few evenings OF the comets appearance to ner
init tory measurements work of this kind
requires the best atmospheric conditions The
observations made in sets of ten and each
result quoted is thus obtained by thirty or forty
separate measurements
June %, to o'clock a. m. three sets pave os
the proportion of the light of the comet which WAS
poarized "a per cent. June 30. | to . O'Clock a.
M, three sets gave mean of 1913 per cent July T.
IL to IL O'Clock p. m. and LATER four sets pave :,
mean of 10 per cent. July 3. IL to II o'clock u. H.
four sets, made under most excellent atmospheric
conditions, gave mean of 17.3 per cent polarized
light.
haps to the atmospheric conditions but il Is NOT i'm
probable that the proportion of light poarzod was
itself somewhat variable. considerable di1ninu
ton in the amount of polarization ut the later
is evident corresponding to the changes in the posi-
tioRof the comet and the angie ut which the Eyht
reflected.
The fact of polarization shows that 4 LARGE norton
OF the light of the comets tail is reflected sunlight
and the percentages found indicate that the latter
npaiit nte afprp ri nf
greater than would be found if the reaecting mn
terial were composed of solid Masses and indicates
that the matter of the tail is in the form of ras or
vapor The comet vi wed with n small spectroscope
showed the ordinary comeary bands superposrd
upon a relatively bright continuous Spectrum no
would be expected from the circumstance that il
shines partly by its light and partly by that de-
rived from the sun.
The origin and nature of the gaseous matter which
forms the TAIL may be Inferred from the results q,
recent discoveries concerning the relation between
comets and meteores The orbit OF one OF the oreot
meteor-streams "A deduced by Professor H. A. N,yv
ton was found to coincide essentially with that of a
well-known comet, and similar coincdenc.s of cam,
ctary orbits with those of swarns of neteorc bodies
have since been made out in other eases Furih.r
more, we have "A complete chain of evidence show
ing the essential identity in character of fbo
meteoric bodies of these great streams and of the
sporadic meteors with those meteorites which have
descended to the surface ;. the earth
Now in some recent investigations by me il vvas
found that these meteorites contain large ouonti-
ties of gas, with considerable proportion of wafer
and that, at Il temperature far below that of red
heat gas Is given of at the rate of from one TO more
than two cubic inches for every cubic inch of the
meteOric substance besides the water vapor he
gaseous product IL a mixture of hydrogen carbon
dioXide and carbonic oxide, the two latter in the
greater proportOn, with Ette marsl-ras and
nitrogen. lnclosed in a Vacuum-ubc at low ures-
sure, and made luminous by an electrical dis
charge, the meteoric gases give a spect11IIn
which, under suitable conditions, is essentially the
same as the usual colnotary spectrum OF bright
bands. The lines due To hydrogen also appear when
the discharge ~ somewhat intense or the tuhe mar
row. IL The cometary spectrum We're sufficiently
bright we might expect that they would be seen in
II also. IL Will be matter of interest to learn
whether these lines have been detected in the sner
trnn OF the comet Whom at its brgh tost or whether
the Line IN the violet, reported by Dr. Draper and
pr hSgis as Appearing IN their spec troscopic pho
tosrapls, may not prove TO be due to hydrogen or