The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1869-09-16

scope without the aid of an eclipse. Professor
Young has been giving much attention to this
subject, and has fitted up very efficient instru-
ment for the purpose. During the eclipse OF
last month, he was stationed at Burlington,
Iowa, and shortly before the first
contact was due, he found that
| there was a solar prominence located at the spot
| where first contact must occur. He therefore
fixed his spectroscope with the slit radial to the
solar edge at this point, so getting prominence
! spectrum whose width was determined by the
| height of the prominence Closely watching
this, he presently found that it began to narrow
steadily, and at the instant that it became
first contact. From the first photograph
showing contact made by the Phia-
delphia party at the same place, Professor A. VI.
Mayer, who had charge of that division, calcu-
lated the time of actual first contact, and found
that il came within two-tenths of n second of the
record made by Professor Young.
SPECTRUM OF THE CoRoNA.-During the to-
tality of the late eclipse, Professor Young gave
special attention to observation of the corona
with the spectroscope. He found that in place
of a subdued solar spectrum which would have
been anticipated from the reports of former ob.
servations, ii yielded spectrum of bright lines.
The most prominent of these he was able to
measure, and found its position rs that in-
dicated by 1474 on Kirchhoff's chart.
Two other fainter ones were noticed,
but there was no time to measure them. Pro-
fessOr Young writes that he finds, by graphical
projection, close correspondence between this
principal corona line and the brightest of the
IA,
the 18th of April, and indicated by him as occu-
pyng the position of 1850 on Higgins chart.
Professor Young also considers that the two
fainter corona lines observed, but not measured
by him. correspond with aurora lines 1890 and
14C0 of Higgins chart, observed by Professor
Winlock. on the occasion above noticed. From
these observations, Professor Young hazards the
conjecture that the solar corona Is, in fact,
permanent aurora.
THE CORONA NOT PoLARIzED.-Wit the
above observations and deductions made by
Professor Young, agree exactly those which
were made ut Mount Pleasant, Iowa, by
Professor E. G. Pickering, who with spectre
scope observed no dark lines in the general light
from the total phase, and with polariscope ar
ranged on the plan used by AragO in his study
of polarization, found no trace of this con-
diton in the light from the corona.
SOLAR PRoMINENCEs AS SEEN AND AS PHoTO-
GRAPHED.-It will bc remembered that in De La
Rues photographs in 1850, several prominences
were conspicuousy depicted which were not seen
by any of the observers. This no doubt results
from the great difference in actinic force be-
tween the light from the corona and proml-
nences, when compared with their luminous
intensity, the corona appearing intensely bright,
but being very feeble in actinic effect.
English View of the Eclipse.
The London Spectator says:-
1t is a particularly fortunate circumstance
that the great eclipse of August has been wit
messed under favorable circumstances, for there
will not be another total eclipse of the until
the end of the year 1871, and then the duration
of totality viii be exceedingly short. After that
there will be no total eclipse till November,
1872 and this eclipse will be of no value at all,
so far as observations to be made during totality
are concerned, since the totaity will not last
more than few seconds. Indeed, the eclipse
will be otso singularly indefinite character that
astronomers cannot say for certain whether it
will be total or annular. Probably it will begin
as an annular eclipse, become total as the
shadow sweeps rapidly across the earth's sur
face, and end rs an annular eclipse again; the
point OF the moons true shadow Just reaching
the protuberant part of the earth's Illuminated
hemisphere. Be this as it may, it is certain that
there will be no possibility of observing the red
prominences.
Thus, had it not been for the success with
which, as we learn, the American astronomers
have been able to observe the important eclipse
OF August z, our solar physicists would have
been forced to content themselves for several
years with the results Of the eclpse-eXped-
tions of last year. This would have been the
more unfortunate because that was the
first eclipse during which astronomers
had been able to avail themselves of the power
of their new ally, the spectroscope. Many
questions of extreme importance have arisen
during the past year as to the significance of
several observations made in India in 1868; and
astronomers looked with interest to the eclipse
which has just taken place to resolve their diff
culties
The eclipse of August was in many respects
inferior to the great eclipse of August Is, 1868.
In 1868 the moons disc overlapped the sun Cat
the time of central echpse) by an amount equal
to nearly thirteth part of the suns apparent
diameter, and thus the totality lasted several
| minutes. This year the moons overlap was
| about fifth less and the duration of totality
was proportonately reduced. Still the eclipse
was an important one, since it is comparatively
seldom that even so near an approach is made
to the exceptional magnitude of the great In
dian eclipse The recent eclipse, too,
was characterized by certain very
favorable features. The moons shadow ira
versed a region of the earth's surface which was
| for the most part accessible to practical astrono-
mers. The Americans had no occasion to un-
dertake long and expensive journeys, since the
eclipse visited them, so to speak, at their own
| doors Some Of the principal American obser-
vatOries lay quite close to the line OF central
eclipse others were not so far off but that large
and powerful telescopes could reaally DC caIrleu
! to some spot upon the central lne' IhGh,
! again, the important processes OF photography
were not interfercd with as in lndia by the tre-
| mendous heat Of the climate. Major Tenant
mentioned last year that he had had great difli-
| entities to encounter owing to this circumstance.
! The American astronomers, among whom are
| some of the most successful professors of celes
tial photography, were subject to no such an
! noyances
One result of the American observations is
| very interesting. Last year there was some dis
| crepancy between the various observers of the
spectra of the prominences, as to the position of
those bright lines which indicate the character of
| the promnencc-tlames. So important was this
| discrepancy, that many were disposed to consider
| in this way some eight or nine lines seemed to
| have appeared in the prominence-spectrum
One observer indeed, NJ. Rayet, announced that
| he had seen seven or eight lines Now Jannsen
(himself an observer of the eclipse and Mr..
| J. Norman Lockyer, who independently dis
| that the brUbt lines of