The Portland daily press., 1886-12-31
THE LICK TELESCOPE.
Marvellous Work on the Great
Lenses.

The two great lenses for the Lick telescope,
on which the Messrs. Clark Of Cambridge
have been so long at work. are now compile
ted and have been shipped. The plan adj
opted for shipping the double lens, worked
out by Capt. Fraser, was as follows: The
two glasses were first wrapped separately
in fifteen or twenty thicknesses Of cloth
drawn very tight The cloth Is, cotton, and
in order to make it soft and perfectly free
from grit was washed many times and thor
oughly beaten. Next to the cloth came a
thick layer of cotton batting and then lay
er Of paper A box made Of wood and linen
with felt contained the glasses, the felt lin
ing Of the box coming next to the paper
The lenses with their covering were packed
tightly in this box. The shape, OF this box
conformed to the shape Of the lenses. The
felt was attached with glue, so that no nails
will be anywhere near the glass. Outside
Of this wooden box and enclosing 1t was
strong steel box, about the shape Of cube.
The wooden box was tightly packed into
this steel box was another steel box or chest,
and the inner steel box was kept from touch
ing 1t by large number of spiral springs
covering the whole Inferior of the outer steel
chest. This outer chest was packed with as
bestos, to render 1t fire proof, and both Of the
steel boxes were made air tight and water
proof The outer chest was suspended by
pivots in strong wooden frsHpe, and con-
trivance was adopted for turning the chest
one-quarter around every day during its pro
gress to California. This Is to prevent any
molecular disarrangement In the glass and
avoid the danger Of polarization, IL being
feared that the Jarring OF the train would
disturb the present arrangement OF the mol
ecules unless the position OF the glass was
daily changed and all the lines Of disturbance
thus broken up. The glass was insured Tor
its full value-or rather its cost-S5l 900, and
all the precautions mentioned were taken to
prevent any accident TO it, II would prob
ably be impossible to replace 1t, as Fell, who
cast 1t, and the elder Clark, who ground 1t,
are both old men. The glass was shipped by
express.
There is something almost romantic in the
design and construction Of the monster Lick
telescope. Being the greatest work OF the
kind ever undertaken presenting difficulties
that had never before been encountered; In
viting and suffering drawbacks and disasters
that seemed to be sufficient TO Stagger the
most persistenta and painstaking skill watch
ed from day to day by whole world Of anx-
| ious observers; lowered over and caressed by
| the united wisdom of a generati0n-the lens
has come intolthe world with its great eyclo-
| pean eye ready TO pierce the mysteries OF the
| heavens. Capt. Thomas Fraser, superintend-
| ent. of the Observatory, furnishes some hith-
| erto unpublished and highly interesting in
formation concerning the grinding OF the
L CTOMu-Bldoo iCuo, tue pan dubptCu AtA
| transporting it from Cambridgeport. Mass
| to San Jose. On the subject Of the grinding,
| he says that the closest measurement at COM
mand was the 10OOoth part of an inch; but
| in grinding the great lens it was diseove red
| that even this infnitesimal fraction was too
/ large. A still finer rmeasurementwas required
| in reducing the lens in numberless places to
| thickness Qtself unequaD that would exact
| ly concentrate parallel rays Of light filling a
| circle three feet in diameter to point little
larger than pin. In order to reduce the
| fine measurement already at command, the
| following ingenious arrangement was EN-
| ployed by Alvan Clark Il Sons, makers Of the
| lens: A gas jet was placed before the mirror,
| which sent the rays of light through tele-
/ scope to the great lens, thus magnifying the
rays The magnided light, passing throu gh
i the great lens, was still further immensely
magnifed, and after having passed through
this lens,it was observed through second
telescope and thus further magnihed. In
this way the least failure of the great lens
TO concentrate perfectly was detected, and
there was also determined the amount Of
glass in 1t, at any given point, that had to be
| ground off in order to secure perfect focus.
Thus measurement Of the 2,O0O, ,0OOth part
| Of an inch was secured. Ii took very little
grinding to remove so small thickness Of
glass from giveu point, gentle rubbing
with the thumb being sufficient, as the glass
Is softer than common window glass.