The morning news. [volume] (Savannah, Ga.) 1887-1900, 1892-12-11
MOVING A BIG LENS.
UNCLE SANS STAR-GAzERs AC-
COMPLIsH a DELICATE TASK.

ders to Be Shown By the Govern
ment Observatory at the Fair-As-
tronomy in the Modern Stage.
Washington Letter in Pittsbur0 Dispatch.
Governments star-gszers have been
having a great time moving into the
new naval observatory, which is the
most beautiful building for astrono-
mical purposes in the world, situated
on the heights overlooking Washington from
the northwest Naturally the transfer from
one place to another Of instruments so deli
cate that finger must not ordinarily be
allowed TO touch them, lest their adjustment
be spoiled, is attended with no small diff
Guilty. But the article which required the
greatest care in its removal was the object
lens OF the famous equatorial telescope.
Until the lenses of the Lick observatory
in California were made this was the largest
one In America, being 2619 inches in diam
eter. 1t cost $4,000. This precious thing
was wrapped in the softest of old linen
sheet packed In a box between mattresses.
and conveyed in a spring wagon at q
funeral pace over miles of rood up hill and
down, reaching its destination safely. The
new observatory will have eight telescopes
two OF which the public will be permitted
to use for amusement, one of these having
a 5-inch and tue other 9115-inch glass.
| TO EXHIBIT AT THE FAIR.
| The exhibit Of the naval observ atory at
the worlds fair will include 5-inch tele-
| scope, through which the visitors to the
exposition will be allowed to gaze at what
ever is most interesting IN the heavens both
| by night and by day. 1t Is also intended to
show a picture of the sun on a large scale, a
pencil of rays being thrown through lens
! by mirror forty feet into dark room. In
| this camera obscurs a huge image OF the
orb OF day will appear on screen, showing
the tremendous flames which leap 1000
miles above its surface and also the So
called spots" which are fiery chasms capa-
BILE Of swallowing up hundreds of such
planets as the earth at gulp. At noon
each day the astronomers in Washington
will drop time boil five feet in diameter
| on TOP OF the main building at the fair.
1t has been suggested that the newly dis
covered fifth satellite of Jupiter ought to be
secured for exhibition at Chicago. 1t is such
| a very little one that the star-gazers suspect
1t to be merely a captured esteroid. They
| entertain a like surmise respecting the
| moons of Mars which were originally found
by the big glass Of the equatorial telescope
at the naval observatory here. Possibly the
| earth may capture an asteroid or two some
| day. There doesn't seem to be any reason
why such a thing might not happen.
The great telescope on tho Lick observa-
tory, by which Jupiter's new satellite was
discovered. has an object glass thirty-six
inches in diameter. 1t is expected that the
Chicago University will buy the forty-inch
lens which now lies IN the rough at the
Clark factory in Cambridgeport, Mass.
THE LIMIT OF SIZE.
| This mighty glass was ordered for the uni
| versity of Southern California, but that in
stitution has failed to pay for 1t. Clark thinks
| that he can make telescope lens forty five
| inches In diameter. limit of size exists
by reason of the fact that the lenses bend of
their own weight, and thus their very big
ness may cause them to distort the images
OF objects seen through them. Obviously it
Is not possible TO put anything beneath to
hold them up. All Of these telescope glasses
are cast in Paris by a concern which keeps
the details Of its processes secret. Each one
actually consists OF two lenses. one Of flint
glass and the other of crown glass. The two
together so neutralize all colored rays that
the light which comes to the eye Of the OBJ
server is perfectly white.
The big glass disks are shipped in the
rough to the factory at Cambridgsport.
| Alvin g. Clark is the only man living who
understands to perfection the art OF prepar-
ing and finishing them. First they are
ground down to the proper shape with re-
volviug concave tools, after which the sur
faces are carefully smootned and polished
with fine rouge. Then the lenses are ad-
justed in a big tube like that of a telescope
for trial. The tube is pointed at star, the
image OF which should appear perfectly
round when seen through the glasses.
THE GENIUS OF MR.. CLARK.
But in reality the image Is sure to be more
or less out Of shape, because of inevitable
defects. 1t Is in remedying these defects
that the genius Of Mr.. Clark is chiefly exer-
cised. He goes over the lenses with bit of
rouge on his thumb. and rubs the surface
here and there, polishing away an inf1n-
itesimal thickness in this spot and that, I'M
I'll at length all the rays passed through the
object glass are concentrated at q single
point. Now Bhe image of the star is per
fectly round, and the lenses are finished
Even the finest of them contain many little
bubbles Of air, but they do no harm.
The astronomers Of the naval obser vatory
have looked all over the world for spiders
webs. Such aoSsamer f1laments spun by in
dustrlous arachnlds are utilized in tells
scopes for cross lines extended at right an
giles with each other across the field Of
view, 80 as to divide the latter into mathe-
matical spaces. Threads of cobweb are en-
ployed for the purpose because they are
wonderfully strong for their exceeding
f1neness. aud also for the reason that they
are not affected by moisture or temperature,
neither expanding nor contracting undsr
any condition.
| Specimens were obtained from China
because it was imagined that the large
spiders OF that country would perhaps pro-
duce particularly excellent quality of web.
However, it was found that the best web is
spun by spiders in the United States, such
as are plentiful in the neighborhood of
Washington. Accordingly, expeditions are
made early in June each year, to get from
the fences and barns hereabout the oocoons
of thessbig "turtle-back" spiders Each
cocoon is composed OF a single silken fila
ment wound round and round, though there
are apt to be some breaks in it where
Mistress Spider left OFF work for time
SENDING OUT THE TIME.
The 5-foot time ball to be dropped at the
worlds fair will be made of canvas on q
steel frame. 1t will be wound up each day
to the hight from which it is to fall. and 10
will be set and electrically connected in
suoh a manner that the breaking of the cir
cult at IL noon will release it. The cable by
which it will be controlled has already been
laid connecting the new observato with
the entire Western Union telegraph system
Within thirty days it will be in operation,
the touch OF q button at the Washington
end OF it simultaneously trans
! | hitting nokica Of tina hour QUAR-