The evening tribune. (Pawtucket, R.I.) 189?-190?, 1897-05-28

Iho Great ferkes Instrument - NOW IN
Perfect Adjustment at Lake Geneva,
Wis.-It Will Be Presented to the Uni
versity OF Chicago In July.
In swathing OF cotton, curled hair,
tissue paper and flannel, the lenses for the
great Yerkes telescope at Williams bay,
Lake Geneva, Wis, arrived In Chicago
one morning recently. The big crystals
came in special Wagner car, and a guard,
consisting of Alvan G. Clark, the maker,
and "a corps of assistants, took Turns watch
ing that 20 harm came to the precious
freight
The lenses went from Boston over the
Lake Shore road, and reached the Van
Buren, street depot at 1886 o'clock. I'm
mediately an engine was attached to the
car and IL was taken over the st. Charles
Air Line tracks to the Northwestern rail
road and went on the way to Lake Geneva
station, the nearest station to the observa-
tory. On the car with the lenses was
George G. Walker, trustee Of tho Univer-
sity of Chicago, and several officials of the
railroad company, for the property 10 Of
great value and had been guaranteed TO
be delivered in safety. At Lake Geneva
station specially constructed wagon had
been arranged for to haul the glasses over
the six miles of road to their journeys
end.
Professor Clark went along to put the
lenses In place and see that all Is right be-
fore returning home. Speaking Of. his
work In making the crystals, he said:
"These lenses are for the largest astro-
nomical telescope In the world. The order
for their construction was given nearly
eight years ago by Charles T. Yerkes, who
not only presents them to the University
Of Chicago, but has built the observatory
and placed In 1t the apparatus connected
with II. The principal lens is Al u inches
In diameter and weighs 800 pounds. The
exposed surface when In place win be 20
inches In diameter, ~ inches being taken
up by the casing. ID IL double convex, 2x
inches thick ct the center and thrce-fourths
Of AN inch at the edge The inner lens
is Of flint glass, ooncave form, ~ inches
thick at the center and inches at the
case 1t weighs $40 pounds. The FOCUS 10
90 feet.
"The glass out of which thess lenses
were formed was cast in solid block At
tho great factory In Aantois, France. IL
was made In 1890, but finishing work was
not begun ON IL until two years Later.
"For five years tho process Of forming
and testing the lenses has bsen going on.
The work has been done by q small force
Of men, but it was constant, requiring tho
utmost patience and care. The deviation
of the breadth Of q strand Of a spiders
web would b. fatal t. the purposes Of the
glass. The crystal had first to b exam
ined 10 80 X ID was Without flaw, and,
after this, it wsnt TO the grinding room.
For two years sand, hAe stsel and emery
wMe used, then tho finest jswsaers'
rouge and besswax for another ysAr OF
more. All this tDs tests were made 20
detect any inequalities. During the last
stages tho lonsss wefe set In 60 foot
tube, so know that the object glass and
its mate are perfect"
The lenses are worth e85, 900 and are In
sured up 10 full value. The telescope was
ready for use by the astronomers of the
observatory on the day following the ar
rival of the lenses. A special train carried
the trustees Of the University of Chicago,
President Harper, members OF the faculty
and number of invited guests to inspect
the great instrument and its powers. The
formal presentation by Mr.. Yerkes will
take place at tho convocation in July.
Among the advantages which may be
expected to accrue to science from the
completion of this telescope will be better
facilities for photographing sun spots. 1t
is better adapted for Investigations of this
character than any other existing instru-
ment, not only on account of its large
aperture, but particularly on account of
its great focal length. The image of the
sun at the focus of the telescope Is nearly
inches i'm diameter and is therefore par
tioularly we'll adapted for work on the de-
tails of the suns surface. Chicago Times
Herald.