The daily morning journal and courier. [volume] (New Haven, Conn.) 1894-1907, 1899-09-13
THE PARIS TELESCOPE OF 1900.


mouth, Mass.
THE PARIS TELESCOPE OF 1900.
A Gigantic Instrument Making-For
the Exposition of the End of the Cen
fury.
One of the most remarkable features
of the coming universal exhibition will
be the gigantic telescope with which as
tronomers in 1900 and succeeding years
will explore the heavens. Hitherto
merely vague ideas have been formed
in regard to this great siderostat which
is of such deep interest to the scienti-
fic world but last Sunday the writer
CHANGED to meet M. Eugene Antoniadi,
assistant astronomer Of the Juvisy OBJ
servatory, who with great courtesy,
placed at the disposal of the readers of
the Tribune such facts and information
as will present a precise and accurate
description of this marvellous instru-
| ment.
| 1t was at the iniative of M. Francois
| Deloncle, minister plenipotentiary in the
| French diplomatic service, that group
| of amateur astronomers decided to de-
| wise for the international exhibition an
| instrument of exceptional dimensions
and power, far exceeding anything before
attempted With this end in view, it
was determined to give the object glass
a diameter of Los meters, or 1872 inches
that is, 9.2 inches more than that of the
celebrated Yerkes glass of Williams
Bay, Wis, and 1872 inches larger than
that of the Lick telescope, at Mt. Ham
ilton, Cal In order to utilize such an
aperture to the best advantage, and es-
pecially to check as far as possible the
obnoxious effect of chromatlc aberra-
ton, it was decided not to subordinate,
as usual, the optical work to mechanical
difficulties by a reduction of the focal
distance, hut boldly to give the tube the
enormous length of so meters, or nearly
200 feet.
To mount such an instrument on an
ordinary equatorial foot would be prac-
tically impossible, for, to say nothing
of the tremendous weight of the tube
and the consequent instability and flex-
ures to which it wood be exposed, the
dome destined to protect it ought TO
have diameter of at least 210 feet or "
feet larger than the cupola of ST Peters
in Rome, and 1O3 feet more than the
dome of st. Sophia at Constantinople.
But this is not ALL Owing to the APP
parent diurnal swing of the heavens
around the polar star. the dome ought
during the observation to be in constant
motion, SO as to have it's opening al
ways in front of the object-glass, NOV
ing with velocity of SO feet an hour.
The eye-piece would of course, also
Jiy,fr M and
obvious that the acrobatic feats the OBJ
server would have to accomplish in or
der to follow the movements of the in
strument would better suit vigorous
athelete than the delicate frame of the
man Of science.
These difficulties have been surmoun-
ted by the wise conclusion of the COM
mittee to adopt the siderostat type of
mounting, such as has been perfected
by the French physicist, Leon Foucault,
a man of remarkable mechanical genius.
M Antoniadi uses the expression per
fected by Foucault advsedly because
he points out that the principle Of the
siderostat was known a hundred years
ago, when clever London optician
named Brown constructed "a telescope
whose tube was always horizontal, and
in which a plane mirror reflected the
image of the object to the eyepiece.'
The sierostat thus consists of a fiat
mirror, so mounted that when clock
work motion Is applied to it it will
send in the same fixed direction the rays
impinging upon it from a heavenly
body telescope directed along the
reflected beam will then enable the OBJ
server to scrutinize the object without
troubling himself about the motion.
The fixed tube Of the great Paris re-
fiector is Of steel very slightly less than
inch thick, and weighs some q tons
It's diameter is SO inches. The cylinder
is formed of "a seperate parts screwed
together, and rests on eight cast-iron
supports, placed on eight stone pillars
In order to facilitate expansion by heat
the supports can glide on system of
rails attached to the piers
There are two object glasses, the one
for visual observations, the other being
reserved for Photographic work. Each
glass weight 1900 pounds. They are both Z,
mounted on truck gliding along a rail
way, thus allowing of their easy trans
fer in front Of the tube, The eyepiece |
is also movable on a railway, and the |
focusing is affected by a screw so inches
long, uniting the two tubes. Should the |
mirror of the siderostat not perfectly !
follow the object under scrutiny, then |
the corrections in right ascension and |
declnation can be made without diff |
Guilty from the eyepiece end by most |
ingenious contrivance. The siderostat |
proper, which weighs some 45 tons, con-
sists of a huge brass foot measuring Is |
feet in length and as much in height, |
and resting on a marble pier. The dia- |
meter of the great mirror is 1874 inches, |
or rather more than 61@ feet, and it's |
weight, mounting included, more than |
615 tons. 1t is held in equilibrium by a |