Charlevoix county herald., 1920-08-27
AMERICA MAKES
BIC DISKS NOW
Lens Manufacturers Solve Diff
cult Problem With the
Aid of Scientists.
CATCHING UP WITH GERMANY
AZ Mechanical Difficulties In Making
OF Large Telescope Disks Have
Been Overcome-Process
Is Delicate One.

New York.-Large telescope disks
are being made in the United States.
All mechanical difficulties have been
overcome, according to an announce
ment made by DR.. George w. Morey,
a member of the American Chemical
society.
This remarkable achievement is due
to preparation and handling of the In
gradients required for pure and flaw
less glass and is the result of expert
ments begun at the outbreak of the
world war, under the auspices Of the
geophysical laboratory of the Carne-
gle Institution In Washington.
Catching Up With Germany.
Before 1914 practically all the OPP
teal glass in the United States was
imported from Germany. When the
United States entered the war the
field glasses, range finders, telescopes
and other instruments of precision
used by her army and navy were
equipped with lenses fashioned be-
yond the Rhine. Private citizens even
loaned or contributed opera glasses
and binoculars to the fighting forces.
Optical glass Of fine quality, howev-
er, is now to be had on this side of
the water The climax of this achieve
ment of Industrial chemistry has been
reached by American makers in the
manufacture of lenses for telescopes.
At first disks which strengthened our
view were made three or four inches
in diameter. Recently a special four
and three-quarter inch lens was
ground for Lowell observatory at
Flagstaff, AriZ.
The first nine and one-half inch disk
was turned out last December. Six
others have since been made and de
livered. AS their diameters increase
disks are made with greater difficulty
Finally, on February Is, 1920, the first
perfect Pinch disk was furnished
and q large optical glass corporation
now lists this size for short-time deliv.
cry.
Making Larger Disks.
lAc lCAl Size dliCllptCu was ~
inch disk, In the manufacture Of which
the problem was still more complex
Several flawless ones were produced
but they cracked In the annealine
process. American ingenuity was
brought into play to devise means Of
slowly cooling these immense plates
of glass, so that they might be free
from the strain so likely to destroy
them. Experiments by scientists OF
the geophysical laboratory showed ex
actly how slowly their temperatures
must be lowered, and the cooling
schedule outlined was closely fol
lowed. Owing. however, to the ex
IRENE cold weather Of last March and
the shortage of gas, this schedule could
not be followed. One splendid disk
strained and broke just when nearly
ready to be taken from the oven.
Equipment hitherto used was then
scrapped and an electric furnace was
specially designed to meet the needs OF
the problem by experts Of an electric
company. This device is thoroughly
insulated and provided with an auto
matte appliance which will hold the
temperature absolutely constant to q
fraction of degree while the glass IL
being treated to remove strain. The
temperature can be dropped few de
grees q week.
With the aid of this furnace now ir
process Of construction 1t is believed
that the last difficulty In the way OF
the American manufacture of the
largest disks will be overcome. Or
ders have already been accepted fol
the production of several large guar
anteed disks, including one pair Of the
1S-inch size for refracting telescopes
and 36-inch disk for a rejecting tel
escope. The furnace will receive the
40-inch size. When that goal has been
reached, the company will continue
the development, so that eventually
the largest and finest disks In the
world will be American made.