New-York tribune., 1899-04-17
THE PARIS EXHIBITION TELESCOPE.
NOT MADE TO swINa-AIpED By AN ADJUSTABLE
MIRROR.

NOT MADE TO swINa-AIpED By AN ADJUSTABLE
MIRROR.
For a long time there was reason Tor dououns
whether the telescope which had been proJec'eo
for the Worlds Fair Of 1900 would really be con-
structed or not, but recent reports encourase '"o
expectation that 1t will be finished even II II does
not fulfil all the hopes that have been exci'eu III
regard to 1t.
The mounting OF a large refractor involves sucn
serous engineering difficulties that the successful
erection and use of the instruments IN the LicA
and Yerkes observatories are Justly regarded as
wonderful achievement. aside from the purely as
Economical aspect Of the undertaking. Ihe FORMER
telescope has an obectglass sc inches In diameter
and the latter one an objective 40 inches across.
NJ Deonce contemplated lens ~ inches III oaii'
eter for the Worlds Fairl Now rigid as glass Is
supposed to be- there can be no question that aiter
a. certain limit has been reached In size O lens wiz
not have precisely the same curvature when II Is
held horizontally by its utmost edges and wneh IL
Glands unr,ght There will be sag In the middle
IN the ono position that will not be observed IN
the other The slightest reformation OF this SORT
however destroys the optical properties Oh tne
glass.
When NJ Deloncle first talked about this tnhs
he was bothered mainly by the money question:
Rut when he went to the great teescope-makers
OF the world Clark. Brashear. Grubb ana the
Henry Brothers, and consulted them about MAKING
his lens, he faced a new embarrassment ihey
showed a singular unwilngness TO take the Joo
except under conditions that would relieve tneD
from the responsibility Of failure. Even after M
Deonce decided not to mount the instrument 50
as to swing but to keep 1t In one position these
men were not any too eager to consider the matter'
However, Mantois. who manufactures the glass
out Of which the lens Is to be shaped mas rece'eo
his order and the completion OF the objective as
well as Of the mirror to be used with the telescope
intrtt otad tn at
named Gauter.
The general plan to be pursued IS to mount the
telescope In tube sixty metres long (about hun
dred feeD and in horizontal position. and to nave
1t remain stationary. In front OF 1t. at con-
venent distance VIII be placed r. round 9b mrr9 ooD so
other object to be viewed and reflect II 3 nt0 oHe 5ne
the movement Of the skies. This device is called
sdepSsa When us confined to the study Of the
stars In the present instance the mirror Will nave
Inasmuch as an attempt will be made to obtain
photographs with this telescope an ooject-gaSss 81 IS
and ADJUSTED III" in frame side by side with the
b rsme VIII be d along ana desIred
brought into place. The optician then , mas 10 10
this character usually requires years, and there is
room for anxiety as to the excellence OF the lenses:
also from the haste which now seems to be in
evtable in their production. III,
ranged that an eyepece can be applied or sensi,
tive Photographic plate put there, and suitable
screen will be erected this end OF the instru-
inspection may be thrown where 1t may be seen by
several hundred persons at once. II NJ. Deloncle's
dreams are fully realized, the picture Of the moon
thus afforded will prove a great popular attraction
the workmanship on the lenses shall prove to have
been of the highest order a magnifying power OF
only about fifteen hundred or two thousand diane
ters can be used in the eyepiece. whereas at the
Yerkes Observatory in this country power OF
The quality Of the instrument may not be all that
It's Protectors have fondly hoped for, therefore.