, 1888-11-08
A BIG TELESCOPE EMS.


California, located at Los Angeles, ask.
ing for information as 10 a forty inch
lens, and intimating that an order for a
telescope to eclipse that at the Lick OBJ
servatorv would soon be sent.
A correspondent who was present
turned his attention to the numerous
lenses OF different sizes and in various
stages of manufacture while Mr.. Clark
was reading the letter. He had just
been talking with the man who had made
eyes that could read patent medicine
signs on the moons rocks with regard TO
the possibility for further advance in as
Economical researches, and he feared the
letter might make it necessary to shorten
his visit. MI. Clark's eyes twinkled as
he read the letter. Then, without a
word of comment, he handed the missive
to the reporter and resumed the patient
rub, rub, rub of a small lens glass on the
polishing block.
"What do o think of that2' be
asked, when the reporter had made a
careful mental note of the contents of the
letter.
II thought it had been stated by some
savants that it was impossible to finish a
lens any larger in diameter than that
sent to the Lick observatory" the repor-
ter said.
81 know such a statement has been
made" replied Mr.. Clark, but l do not
indorse it. I've been making telescope
lenses now for q good many years, and /
ought to know something about it. If l
can get the glass the proper size there
will be no trouble in making a lens forty
inches in diameter. Id make a five
fpotpr if INV kfa ToS cD,ral lone apn,ph -
do you mean to say that there is a
possibility in the future Of having tele-
scopes five feet in diameter"
Il don't see why they should not be as
large as that. But mind you. it would
take about one mans lifetime to make
such a lens. In the first place, it would
be necessary to get a piece of glass alb
solutely perfect in every way. The
slightest flaw or variation in density
would spoil it for a big lens. 1t might
be a generation before such a piece of
glass could be manufactured. Then it
must be ground and polished by hand.
But l believe such a lens can be made,
and l believe il will be made"
"Wlu it be of any practical advantage
to astronomers"
Certainly it will. Its increased mag
nifying power will be in proportion to its
increased sized. Take this forty-inch
lens that has been mentioned as an ex-
ample. Its size would be one-ninth
larger than the Lick observatory lens.
and it would make given objects appear
nine times larger or nine times nearer.
Increase the diameter of the lens and YOU
will increase the power to examine
worlds that have not yet been seen. If
a lens five feet in diameter is secured, it
will bring the moon so close that we can
see every nook and granny on its surface.
As for new stars, there is no limit to the
discoveries that could be made. 1t would
revolutionize astronomical researches"
Had you thought of making n larger
lens than that in the Lick telescope before
you received this letter."
ooh, yes. l am not surprised at re-
ceiving tins letter, for when / was in
California a year ago the president of that
university intimated that they should
want a larger telescope than that on
Mount Hamilton. There is a wonderful
amount of interest in astronomy in Cali
fornia. All sorts of people are studying
the science. This five inch lens | am
polishing is for a telescope l am making
for the president of that university. Iii
for his personal use, and he begged me
to make it with my own hands, so / am
pegging away at it when l get the time.
l have also filled other small orders from.
that state. In addition to those small crdcg1
l have received no less than three letters
from different colleges asking if 1 could
make a forty inch lens. Ihavo written all
those persons that l was ready t. accept
any and all orders for a forty inch lens.
In fact, | was so sure that there would be
a demand for such n lens that | gave an
order to the glass men in Paris to save
for me the first large mold that they sue.
ceeGed in getting out. may get it in a
few weeks and l may have to wait
months and weeks for it. | heard the
other day that they had cut out two
extra large plates and were finishing
them for the exhibition next year. Il
it's true, | shall secure them if money
will do it,
What causes this delay?"
lit Is all in the casting, " was the reply.
"Au these lenses are made in France,
near Paris. They are making them all
the time. They melt up lot of glass,
and when it is of the right consistency
they set it aside to cool. The glass is
melted in huge pots, and after every
casting the pots are broken away, leaving
a large mass of glass. Then they examine
it and test it to see if it is suitable to split
up into lenses. 1t must be Just right Oh
II must be melted over. They have orders
for all sizes of lens, but they do not con.
slider those orders until they get the bloch
of glass. The least indication of strie OF
sediment viii show that it cannot be uset
for larger lensasN Then they break it III
TO see if they can use It for small ones
There are generally enough imperfection
TO ruin the block for large lenses. If nont
is visible to the eye the block is testet
with the polariscope, to see if it is of ever
density throughout. If all the condition!
are perfect, then they will split up the
block and get out a large lens in the
rough. If they succeed in doing tina
there is still great danger that it will b.
broken in the first handling to get it down
to the proper size for grinding and polish
ING. After that il ~ccomDliSna1 tba ,r,r-