Evening star. [volume] (Washington, D.C.) 1854-1972, 1928-01-22
LARGEST GLASS /.
CAST BY BUREAU
Optical Lens Completed Here
Establishes New Record for
Perfection and Size.

Science has passed another milestone
on III march of progress in physics
ana the physical sciences.
A thrce-year effort by the Bureau of
Standards 10 create the largest perfect
r!22e OF optical glass in the world was
crowned with success Yesterday when
Ire lid OF a GlaSs-caSting furnace was
raised from 7o-inch. 3-ton disk OF
glass, after more than nine months of
cooling and anneallng. and the glass
was found. on first examination. to be
Perfect. After necessary drilling. polish
ing and figuring the great disk OF glass,
the largest ever cast in this country
and the second largest in the world,
viii be installed in the rejecting tele-
scope of the Perkins Observatory at
Ohio Wesleyan University. Delaware.
Ohio. At the price of Sc a pound.
charged the Navy by the Standards Bu-
reau for making optical glass the huge
disk would be valued at S2l.000
II will cost the university only in
the neighborhood OF $4,000, according
10 Director George K. Burgess of the
bureau. who entered into an agree
nlent With the Ohio institution to
cetray the expense of the TEDIOUS en-
pertinent. The only other piece OF
optical glass comparable in size TO the
one whose casting was completed yes
teroay is the l00-inch disc used in the
telescope at Mount Wilson which was
cast in France. Government scientists
Ray this disc is very imperfect and does
no approach the perfection OF the
glass which vas revealed yesterday 70,
the first time
Visitors Witness Opening.
Suspense and the knowledge that a
grea. scientific experiment was about
70 be conSummated held breathleSs q
distinguished group of visitors TO the
optical glass laboratory of the bureau
yesterday as they stood about a Jagged
hole in the concrete floor of the barn
Ike building and watched workmen
manipulate the machinery which slow
ay raised the liz from the great disc
snd revealed the great glass circle. A
n. Finn. director of the optical glass
laboratory, and p H Bates and d.
"A. @. Tool. many months before had
mixed together thousand pounds of
outlet toroken glass; and 1900 pounds
OF sand and chemicals. watched the
mass glow 10 white heat under the
excitation OF powerful electric cruel
bic, and had then poured il into the
Erick-line6 kiln which was ready TO
receive 1t. Carefully IL was stirred BY
hand for SIX hours and from the time
the lid was clamped down. on May |
1927. II had never been seen until |
yesterday.
During the weary months which |
stretch back 10 that day last May. |
careful hands tended the great disk !
snd slowly dropped the temperature |
from the original 1900 degrees Fahren- |
heit through the annealing process al !
$50 degrees TO the attainment of room |
temperature last Monday. Five more !.
days were allowed 10 bring the disk |
down TO proper temperature for un- |
covering, and Yesterday. on one OF the |!
coolest DAYS of the Winter. the lid was |
removed
II looked like nothing more than
sheet Of calm water. without a ripple |
rs the great lid itself weighing hun.
oreds Of pounds. was slowly lifted from
the crucible wherein lay the hopes and
ambitions Of dozens OF. men and the
cradle OF great scientific experiment F!
A broad smile overspread the face of
Mr. Finn and his associates as the I'D
vas slowly raised and moved to one
side 10 reveal what was apparently q
Hawiess piece Of glass. with the fire
its il-inrh thickness. Then congfatula-
tons broke forth for Finn and his CO.
workers on their care and exactness
Concealed for Months.
During ali the months since the glass ,
vss cast there was no way 10 ascertain
what lay under the lid of the furnace.
!o~ the slightest bit OF foreign matter
IN the glass or sudden change in tenn
pera'ure might split 1t into fragments
Within FIVE days the bureau staff
viii start on another and quite as ardu- |
ols a Job IN connection with the final
process Of preparing the big disc for
Use infringing the heavens closer TO !
earth through the eye OF the telescope |
The NEXT step necessary in preparation !
r. 70 drill hole at the apticai axis OF |
Is 70 Grill hole al the optical axis of |
refused becauSe Of the possibility OF |
fracture o! the glass Then 1t viii be |
sent 10 an opt.cian 10 be ground pol |
ifhec and figured on one surface until |
j. becomes parabolic, with the property |
Of rejecting parallel rays o! light TO a |
focus.
Mounting O. the great telescope In !
which the cisk viii gO has been COM !
pletec out IN Ohio By Warner and !
Ewazey Of Cleveland. and with a disk
temporarily obtained from Harvard !
University research work was begun al |
Ono Wesleyan University The need /
Tor larger disk prompted university I
Authorities 70 urge the bureau 10 at /
tempt the casting. after several Amer /
ican glass n3anu!acturer:t had refused |
10 guarantee complexion Of the work /
-Four unsuccessful attempts were made /
D"'Te ine present perfect piece Of glass !
was nfaAF cas-. under new system /