The Portland daily press., 1896-11-21
BIG YERKEs TELESCOPE.
1t Is the Largest of the Sort in the World.

| oooois7eorJ at Lake Geneva will
ready for dedication and occupancy b
the Goth of this month, according to
Chicago letter to the New York Sur
The observatory is famous for what 10
to accomplish. 1t will have the larees
telescope in the world-larger by NOR
than 10 per cent than the Lick telescop
in California.
Word has come from Gam bridgeport
Mass. that the great lens which Alval
Clark has been grinding for the tele
scope Is ready to receive it.
Clark Is the maker of the greatest tele
SCOPE lenses in use in the world. n
ground the twenty-six inoh glass whicl
Is In the telescope in the naval observa
tory at Washington. He ground tn
thirty-six-inch glass in the Lick observn
tory in California. His business i
solely the grinding of lenses. He doe
not cast them. A Paris factory doe
this by secret process which NJ
American glass manufacturer has ye
been able to penetrate. Two disks ar,
cast for each lens-one of flint glass and
| SHS VI SAo"h SAo5os \ A0 WV AcubThllZt
the colored rays SO that only a whit,
light comes to the eye of the observer.
| The disks for the big Yerkes lens were
cast in Paris more than four years age
on an order for the University of South.
ern California. They cost $40. coo in the
rough. They were shipped to Mr.. Clark
and lay in his laboratory awaiting pay
ment. The University of Southern Cali
fornia failed to pay for than. About
this time the University of Chicago
was asking public-spirited citizens for
endowments, and Mr.. Ysrkss, who is one
Of the wealthiest street railroad capital
lists of the West, off cred to pay for an OBJ
servatory to cost $500, 000. The offer was
accepted and arrangements were made
with Mr.. Clark to grind the big lens in
his laboratory for the new observatory
The grinding has taken about two and a
half years and has cost about $50, 600.
The cost OF lenses increases In proper
tion to their size. The 26-inch lens of
the naval observatory cost only $50, 600
altogether.
The process OF grinding lens IL neces-
sarily slow, for single error might de-
stroy the $40, 900 worth of raw material
In 4o-inoh glass. The rough disks are
ground down with revolving conoave
tools. Then the surfaces are smootaed
and polished with rouge. T he lens Is
tested by looking through 1t at ia star.
Handling it for this test is no small task
for the lens and Its ring weigh about
1000 pounds
At its first trial, the lens invariably
shows defects. No mechanical process
has over made lens perfect If such
thing were possible, Prof. Clark would
not have the monopoly of max ing great
lenses. 1t is Prof. Clark's mission to
60 over the lens with his thumb, rubbing
down with rouge any minute inequality
Of the surface and bringing it to it's
perfect condition.
They call the Yerkes lens 40-inch
glass. Its exact diameter is Al 3-S inches;
the crown is about SO inches thick at the
middle and IA inches thick al the
outer edges. The weight of the crown
glass alone is 205 pounds and the flint
glass 80 pounds. Prof. Clark does not
call the Yerkes glass his limit. He
thinks he can grind a perfect lens As
inches in diameter. The difficulty In the
way Of making larger lens is the
weight and f1exibility of the glass. A
glass larger than 45 inches in diameter
and lneauring only about inohes AZ the
hfnJy 81 IL
weight. In fact, there are those who
believe that the 45-inoh glass ia impracti-
cable.
The transfer of one of the great len4es
is very expensive and hazardous mat
ter. When the naval observatory at
Wasin gton moved into Its new quarters
four years ago, the moving of the Clark
lens WAS the most delicate operation in
the process. Half a dozen professors took
the glass from the telescope with infinite
care. wrapped it in old sheets. put it be-
tween mattresses, and packed them in a
box which WAS put on springy founda-
ton in spring wagon. The slowest and
safest horse that could be found was
hitched to the wagon, and the procession
M ed at snail's pace over four miles
of rough road. The flimiest bit OF ela g
ware could not have been handled more
than this pair of disks weigh
Ing hundreds of pounds. When big lens
like this goes on railroad journey IL is
wrapped in flannel or old linen, packed in
curlsd hair in box which is mounte
on springs and taken by special car un-
der guard. The journey of the Yerkes
lens from Cambridgeport to Lake |
Geneva will be watched with interest BY |
the whole scientific world. The lens will |
not change cars on til 9 journey and the
engineers Of the trains to which the
'pecial IL attached at the different stages
Of its journey will be warned to handle
heir charge az gingerly as possible.
When the car reaches the erd of its
Journey, at the little town Of Williams
Bay, it will have mile still to- CO. and
This mile will be the siowest IL viii
tIavel. The roads are good and there is
little danger of any accident.
The Yerkes observatory stands on the
northern shore of Lake Genava about