The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1897-05-19
THE YERKES LENS.
AT LAST COMPLETED 1T Is SENT
WEST.
Product of Many Years Incessant
Labor, Its Value is Placed at
$50, OOO-Finest in the World.

Cambridge, Mass, Nav 1s.-From
Clark's lens works. Cambridge, has
been shipped in special parlor car two
discs which form the lens for the
Yerkes telescope, the largest lens ever
made. The car was attached to the
Chicago express. Professor Clark. the
maker of the lens Carl Ludin, his fore
man, who has spent several years in
polishing the great discs. and another
workman accompanied the car.
The greatest care was taken that no
harm should befan the two discs and in
their large cases in the center of the
car they were so adjusted on springs
that the jolting will not damage them.
Guards have been stationed at both
doors of the car and every Drecaution
taken that outsiders ard curiosity seek
ers shall in no way interfere with the
transfer of the lens. Then, too, they
were insured for their full value while
in transit.
This YerSes lens is the largest and
| finest in the world. 1t represents nearly
six wears of careful labor, and com
pleted is valued at $780, 0O The glass
came from the factory of Mantois in
Paris, France. The lens is 4115 inches
on the surface diameter and weighs 515
pounds. The exposed surface, or aper-
ture, is 40 inches, the other inch and a
half being taken up by the casing This
makes it just four inches larger than
the Lick telescope lens, which was also
made by the Clarks and has held the
place of honor in the world of astron-
omy.
The great lens consists of two sep
arate lenses of differing density and
shape, seDarated when in use by a
space of several inches. The outer one,
which comes in contact with the at
mOsphere, is made of a perfect piece
of crown glass. 1t is double convex.
two and three quarters of an inch at
the edge and weighs 2O5 pounds.
The inner lens is made of flint glass,
and is what is known as piano cOncave.
1t is one and one-eighth inches in thick
ness at the center and two inches at
the edge; it weighs 80 pounds.
Both lenses are adjusted in an iron
ring and cell and the total weight of
the glass and iron casing is 1000
pounds.
The focal distance of the lens is 81
feet
The packing of the lens was one of
the most interesting features in their
history. First, they were carefully and
smoothly wrapped in flannel, sewed
tightly at the edges: then they were
covered with several thickneSses of soft
tissue paper and then wrapped in hard
paper and encased in a bed of cotton
batting, silk and curled hair in a strong
box.
This box was mounted upon springs
and placed within a larger box and
packed with excelsior. The springs
within the outer casing, between that
and the inner box, are designed to de-
tract from any jar that the outer case
may sustain and thus save the lens
from the effects of almost any shock
The great glass disks for these lenses
were cast in Paris and a year was
taken up in preparing the material and
casting a, dozen or more before a per-
feet one was secured.
The care, skill and the patience which
have been expended in grinding the
lenses is marvellous. When completed
the lens was mounted in a temporary
telescope tube and tested for so nights
and found perfect.
Had there been a deviation of a spid-
er's strand it would have been useless.