The Lambertville record. [volume] (Lambertville, N.J.) 1872-1968, 1877-10-31
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THE MOST DELICATE WORK IN THE MAKING or
TELEscorz.


Ons OF the most interesting and delicate
operations incident to the making Of teie-
scope, especially very largo one. Il that Of
testing the glasses, after they have been pol.
ished or adapted to the instrument In hand.--
Some of the facts descriptive Of tho process
are THUS given In . recent letter from Cam
bridgeport, Mass.
For the purpose of testing glass Of y tel.
esuope II is necessary that every ray OF light
be excluded In the operation. For this pur.
Pose Mr.. Clark has tunnel under ground
The glass is placed 10 portable receiver I'M
der ground (in the basement) and tho entrance
to the same Is securely closed against daylight,
only . small hole being allowed through which
the eye Of the operator can SEQ the image Of
the object whichris formed 1t the focus.
The tunnel used by Mr.. Clark is $50 feet In
length and about foot in diameter, and as
one peers through IL. the rays Of light, twink
ling and blinking at the opposite end, have
the appearance of q star, 30 complete 10 tho
optical delusion. The necessity Of testing the
glasses In this manner il obvious and many
long and anxious months ara often employed
in perfectiug them before finally adjusting
them In their proper place. The grinding and
polishing process, which In some respects Ia.
wolves the secret Of q superior telescope, is
| very slow and very intricate process.
! Mr.. Clark, ST., once told me that lie could
grind q month on glass and change It's pow
or perceptibly every day, and probably would
not remove tenth part Of grain In weight.
The glasses In telescope, too, are very ssss-
tive, The vital Importance of securing equi.
librium Of all parts of very large instru-
ment is best illustrated BY the fact that
pressure If the hand on the back Of glass,
no matter II 1t be SIX inches in thickness,
produces q fexnre sufficient to distort the i'm.
age of a star.
Another part Of the process, equally inter-
esting, Is thus described by the Hartford
Times
When the glass has been reduced 10 such
seemingly perfect outline as TO render il i'm
possible to detect any imperfection BY either
fine mathematical appliances or eye or touch,
1t u tested not only In the dark tunnel, but IN
actual trial on the stars, and on . terrestrial
target the face Of which II lined OF In math-
Eematical squares. Ifany defect IL discovered
it's locality on the glass is ascertxined by stick
ing patches Of wet paper over the surface inch
by inch, TIL repeated trials show ut longth
that the defective spot has been covered--.
and then the paper is removed, inch by inch,
till the decision Of the last piece is confirmed
by that method.
Then, Mr.. Clark himself takes the glass,
and gently and slightly rubs the offending
spot with the naked bali Of his hnger--using
no powder or anything but the bare skin,
which he keeps soft and susceptible. It Il
surprising that a few slight, soft touches with
the ball OF the finger should remove defect
10 the glass; but that IL what IL actually done.
II the defect is found, on trial. not TO be cn@
tircly corrected, the process ID repeated until
perfection ID attained.
Mr.. Clark, who is 70 years old. and Is as
sisted by his two sons, is still blessed with the
keen syesight and delicate touch for manipu.
lating an object glass which distinguished
him twenty years ago. The 26-inch object
glass which he made for the Washington OBJ
servatory, and which cost alone about $8S, 900,
has already discovered what no other glass,
from Gallleo's down to Proctor's had ever
seen--viz., the moons Of Mars.
| A similar glass, which WAS ordered, at
similar price, some years ago BY Chicago Nc
Corinick, Of "reaper" fame, has never yet
been called for but It Is not likely to wait
long for customer II Mr.. Moe. declines to
to take 1t. We believe Il was while testing
one Of his unequalcd glasses that Mr.. Clark
discovered the companion stsr to siflous.