The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1899-11-19
auLDING THE BIGGEST
OF ALL TELESCOPES.
m Be Great Feature Of the Paris Exposition of IoOO-Foca
Length Is 1917 Feet.

,xoxc the scientific exhibits at the
Y pals exposition OF 1850 the great
IA ,.le.cope will undoubtedly be the
ro.t Interesting and important
...aes showr r. consists, says
e.,e,ssffc American. OF a horizontal
- ssr sset long provided with an OBJ
- - ~ feet In diameter. The image Of
.s.uz~ or stars will be sent through
-. hy the aid OF a Foucault sidero-
- -. thai is 10 say. b. a movable plane
-. The focal length OF the teiescope
- yerkes observatory Is but ss.s feet.
-. II VIII be readily seen that with a
s..~cox,e whose focal length was lsT feet
~anid be almost impossible 30 build a
-. ard mount.ngs which would carry
:, /. estimated tina; a 2l0-foos cupoIa
-..Is have been required. so the use OF a
- ,uf< and a movable mirror for gath
- ne image may be regarded as an
csas;iens solution of "a mechanical Diff
kuss.
"a siderostat ls undoubtedly the most
.tss,sting part OF the instrument. IL
so.s,sss OF large cast iron frame. and
: ofaytded with e1oekwork and devices
:. <snxsng the mirror to follow the ceies-
=, object which IL being viewed. The
s-.~3 il now under construction at the
~w,.s~s manufacturer OF instruments Of
s~ssss.ou II Is 3s5a feet long and the
s.sxs. 1. the same az its length. II IL
,reylted with six ieveling screws which
.r,sr into sockets fixed upon stone base
81 feet high. The hour axis Is actuated
: r,eekwork through the aid OF tangent
srvvs. The part of the instrument
ssvara the south carries the mirror.
vhteh In mounted IN a cast steel cell lined
,ith felt In order TO prevent any contact
4 the mirror with the metal. The equ!l-
ar4upu OF mirror and cell Is obtained by
.esas Of levers and eounterpoises. The
~ Of this mounting floats In a reser-
,,sv a., feet la diameter and containing
,boat sixteen gallons of mercury. Owing
Is he application of the principle OF
lrrhsnedes the movable parts will be re-
AytA Of nine tenths OF Its weight. The
rstem OF the levers and coGnterpoises Ii
4 resi arranged that all of the movable
usts can be actuated by hand even
v4heut the aid of the mercury. The
t,eaj weight OF the siderostat IL S96l0
pvnads, the movable part weighs 5000
uands. OF which the mirror and Its cell
stieh 1870 pounds. A weight OF 30
,sands Ii sufficient TO actuate the clock
yask
n mirror has a diameter of CSC feet:
~ 1853 inches thick and Its weight Is
~ pounds. and 1t was. naturally. the
not dlficuit part OF the apparatus 10
ssasiruet The glass was cast at the
ksrsont works, and special furance
~ constructed capable OF holding ga
ms 81 glass. When the time for casting
frsysd. the mold. s.72 feet in diameter
n. u inches thick. was brought to the
xaAce upon u truck, and then, after
M filed. was introduced into the fur
nee. which had been raised To a high
sE>erature II was then walled up In
u furnace. and the cooling required a
18th Notwithstanding all the preeau-
~ several of the disks that were cast
Ms In pieces with loud noise. The
mportation of such huge disk az
II 10 Paris was difficult matter. and
tsecial train carried Il there without
wing A crane deposited the gigantic
~ on a wagon and II was carried 10
y optical establishment at night. In
M 10 have clear roadway.
y obtain n fine disk Of glass OF such
Hn<nxions was. Of course. difficult, but
hnys II a perfectly plane surface was "A
srh greater one. and NJ Gautier Is TO be
aegvafuiafed upon the ss.c.css which he
b. attained In performing this difficult
HssAtion The polishing machine was
szssd in a special shop protected as
sseA as possible from variations I'm tenn
FEATURE hv a double wooden wall. The
rfnting apparatus consists essentially OF
shrse cast iron plate, covered with an
hsh Of flannel. upon which the glass disk
sm carefully laid