New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1899-12-10

! introduced in a cold provided with a
lantern. The crucible, which terminated in a
| DOME had the form OF a cylinder tnirty-nne
| inches high, with opening in front. Its ca
! pacity was some 800 pounds OF crown and
22OO Of flint glass, the density OF the former
being much inferior to that OF the latter Inc
oven was then walled over. 80 as to leave out
only the mouth of the crucible and heated
slowly and gradually until, at the end or thirty
hours a white heat was obtained. upon IN
Producing the Yitrifabe materials into the
mouth Of the crucible they swelled 10 such an
extent that it was found necessary TO throw
only a small quantity of them at time Fall
ing that precaution the greater part OF the mat
ter escaped into the oven. IL was only aIler
eighteen hours Of successive filings that the
crucible was full. At that time the glass was
replete with bubbles Finally, eight or ten hours
after the last filling the heat was raised To l,OOO
or 500 degrees Centigrade when some or the
bricks OF the oven were melting.
The heating having been stopped glass sam
pies were taken with spoons I'm the boiling mass
and nermitted 10 cool They were then exam
ined microscopcally. When blocks were found
destitute Of bubbles the crucible was opened
and a considerable part Of the surface or the
glass was taken away. so as TO deprive it OF
spots and other impurities.
By far the most delicate operation OF all was
the stirring whose property Is to mix so in
timatelv the vitrifed parts as to give them
everywhere an even density. The stirring was
effected by means OF a long hook raised pre-
yiously 10 a white heat and connected with an
iron bar suspended by a chain from point
above the oven. A wooden handle enabled the
workmen to impart to the agitator a backward
and forward we'll as a rotary motion For
this exceedingly trying work. which lasted from
ten TO fifteen hours, four men, working under
the superntendence of NJ. Mantois, were alter
nately employed.
The reduction Of temperature made the glass
yiscous when the hook whose movements were
thereby rendered impossible, carefully re-
moved The solicited glass then yielded a crys-
tallne sound when struck by an iron rod. But
relocating was necessary in order to avoid the
temper oven and furnaces were once more
walled, the subsequent cooling lasting some I'VE
weeks When the crucible was reopened the
glass block was found broken In several frag-
ments. %,
In order to make flint glass Weighing I9i
mounds glass block of more than l.3OO pounds
was necessary once found, this block, to which
adhered parts Of the crucible. was removed
from the oven and placed on truck Glass
slices were then sawed away from the main
piece in order to obtain polished surfaces csPa ,
bic of thorough inspection. Owing TO the fact
that the sides and surface OF the crucible cooIed
more quickly than the centre and bottom, strI|
were visible almost everywhere In the giass
Scratches near the surface could be easily re-
moved with a saw or by the use OF slick pow
der. Deep laid defects were raised 10 the sur
face and removed by moulding the glass,
placed in a mould of refractory eaftD the
b,ock was introduced into an oven heated to
400 or 300 degrees Centigrade where IL was
smoothed down TO take the FORM OF tne Haouo.
Glow baking then followed. after which the
s,,,erAciai defects were removed other imper-
Tecttons still remaining In the depth or the class
a second moulding was resorted 10, fonoweo
by another baking ana long c"0hhs' ias''"S
some three weeks
No wonder that after all these operations the
actual cost OF the two object glasses came to
$4,000. To transport these valuable lenses from
the workshops OF NJ. Mantos to N. Gautler, the
optican OF the Paris Observatory, the makers
wrapped them carefully in fannels and by
wooden supports fixed them immovably In car
rage provided with pneumatic tires.
The Palais de rOptique, which houses the great
telescope. measures along the axis OF the re-
tractor upward OF four hundred feet. The cen
trail gallery. 220 feet In length and 81 feet wide,
protects the tube OF the instrument. which Is
composed OF twenty-four metallic cylinders, each
s feet inches long and % inches IN diameter all
scraved ,ogather But as the tube is rather mar
row for It's length, and the effect on the eye