Evening star. [volume] (Washington, D.C.) 1854-1972, 1892-11-19

another OF instruments SO delicate that a finger
must not ordinarily be allowed to touch them,
lest their adjustment be spoiled. is attended
with no small difficulty. But the article which
required the greatest care in its removal was
the object lens of the famous equatorial tele-
scope. Until the lenses for the Lick Observa-
tory In California were made this was the
largest one in America, being 261S inches in
diameter. 1t cost $4,000 This precious
thing was wrapped in the softest of old linen
sheets, packed in n box between mattresses and
conveyed In spring wagon at funeral pace
over four miles Of road, up hill and down.
reaching its destination safely. The new OBJ
servatory will have eight telescopes, two of
which the public will be permitted to use for
amusement, one of these having a 5-inch and
| the other 81 -inch glass.
AT THE WORLDS FAIR.
The exhibit of the naval observatory at the
worlds fair will include five-inch telescope,
through which visitors to the exposition will
be allowed to gaze at whatever is most inter-
| esting in the heavens both by night and by
day. 1t Is also intended to show picture of
the sun on large scale. a pencil of rays being
! thrown through a lens by a mirror forty feet
| into a dark room. In this camera obscura
| huge image of the orb of day will appear on n
| screen, showing the tremendous flames which
| leap 1000 miles above its surface and also the
| so-caled "spots. which are fiery chasms cap
| 'DiO Va o""iio"AhS up huAuItdo VI suCH pIblltts
rs the earth at gulp. At noon each day the
astronomers in Washington will drop time
| bali five feet i'll diameter on top of the main
building at the fair. 1t has been suggested
that the newly discovered fifth satellite of Ju-
piter ought to be secured for exhibition at CHI
caSo. IL il such very little one that the star
gazers suspect it to be merely captured
| teroid. They entertain like surmise respect
! ing the moons of Mars, which were originally
found by the big glass of the equatorial tele-
! 81,
the earth may capture an asteroid or two some
day. There doesn't seem to be any reason why
such thing might not happen.
TELESCOPE LENSES.
The great telescope of the Lick Observatory,
by which Jupiters new satellite was discoy-
, cred. has an object glass thirty-six inches in
diameter. 1t Is expected that the Chicago Uni
vecsity will buy the fortv-iuch lens which now
| lies in the rough ut the Clark factory in Cam
bridgeport, Mass. This mighty glass was
dercd for tho University of Southern Cali
fornia. but that institr ton has failed pay for
it. Clark thinks that he can make a telescope
lens forty-fye inches in diameter \ limit of size
exists b. reason OF the fact that lenses bend of
their own weight. and thus dheir very bigness
may cause them to distort the images of objects
seen through them. Obviously 1t il not posi-
bic to put anything beneath to hold them up
All of these great telescope glasses are cast in
Paris by 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 colorcd rays tina. the light which comes to
the eye of the observer is perfectly white.
PREPARING THE LENSES.
The big glass disks are shipped in the rough
to the factory at Cambridgeport. Alyan G.
Clark is the only man living who understands
20 perfection the art of preparing and finishing
them. First they are ground down to the
pnper shape with revolving concave tools.
after which the surfaces carefully smoothed
and polished with fine rouge 4hen the lenses
are adjusted in big tube like that of tele-
scope for trial. The tube is pointed at a star.
the image of which should appear perfectly
round when seen through the glasses. But in
reality the image is sure to be more or less out
OF shape, because of inevitable defects. 1t il
in remcdying these defects that the genius OF
Mr.. Clark Is chiefly exercised. He goes over
the lenses with BIT of rouge on his thumb and
rubs the surfaces here and there. polishing
away an infnitesi,nal thickness in this spot and
that. until at length all the rays passed through
the object glass are concentrated at single
point. Now the image of the star is perfectly
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 OBSERVATORY
have looked all over the world for spiders webs.
Such gossamer filaments spun by industrious
arachnid5 are utilized in telescopes for cross
lines extended at right angles with each other
across the field OF view, SO a. to divide the lat
| ter into mathematical spaces. Threads of cob
web are employed for the purpose, because they
are wonderfully strong for their exceeding fine
ness. and also for the reason that they are not
| affected BY moisture or temperature, neither
expanding or contracting under any conditions.
Specimens were obtained from China, because
il WAS imagined that the large spiders of that
|
excellent quality of web. However, it was
found that the best web is spun BY spiders of
the United States. such plentiful in the
| neighborhood of Washington. Accordingly,
expeditions are made early in June each year to
get from the fences and barns hereabout the
cocoons of the big "turtle-back" spiders. Each
cocoon is composed of n single silken filament
| wound round and round. though there are apt
to be some breaks in it where Mistress Spider
left off work for time. Attempts have been
| made to Use the cOcoons of spiders like those
| of silkwOrms and exquisite fabrics have been
| manufactured from them. Unfortunately it
was found impossible to make the industry
| a commercial success. owing to the combative
inclination of these creatures. When kept to-
gether they will always gobble each other up in
| short time, the final result being a single
very large and fat spider and one cocoon.
! Tho five-foot time ball to be dropped at the
world 3 fair will be made of canvas on a steel
frame. 1t will be wound up each day to the
nelbnt from winch IL Is 10 1al, ana 1t Will be
set and electrically connected in such n manner
that the breaking Of the circuit at IL noon will
release it. The cable by which it will be con-
trolled has already been laid, connecting the
new observatory 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 inst ntaneously transmit
ting notice OF the hour over $50. 900 miles of
wire. When that button speaks the whole
country will listen. and the hands of 10 900
electric clocks all over the United States will
point to the correct minute and second. There
are 1000 such clocks in New York city alone.
| ALI railrays, factories and industries Of every
kind pay attention to the signal Three min
utes before noon each day all the Western
Union lines are cleared Of business. every
operator takes his finger from the kew. circuits
| are opened, and, at the instant when the sun
passes over the seventy-fifth meridian, the
spark OF intelligence is flashed to all parts of
the country. 1t requires less than one-ffth Of
second to reach San Francisco.
DIFFERENCE OF TIME.
The IL O'Clock signal sent from Washington
indicates II am. for Chicago, 10 am. for
Omaha and am. for the Pacific coast. the
United States being divided into four perpen-
dicuiar strips and each strip setting it's clocks
by the time Of the meridian which bisects it
from north to south. Thus each strip is al
ways one hour later than the next strip to the
east. The Western Union Company earns
| about 81 ,000, 600 annually from its electric