The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-12-05

large as could 30 procured, ana whom Dolland
ssgroSt in Il that he remarked 70 KitoS bin 1P:
Is YG e. that make e0i @a f ;%%o is Sn9 E fih shH thing, Ing S shTt
Gully vas !. solved ~ Pierre eaina6d, q watch.
n SThe re a arc two serious SGGSnss diiii sUitEsri IN Making
flint glass; Mr.. Brashenr says. "ono ia
S aSIss q /, Sns .e n nc % Of Re oxide 2, lead;
BOZ or srHciSls when ( e n q state o o.
zontai layers OF tho glass. which in itself would
truly HORIZONTAL sections from the cooled No vs!
bn, this Is an impossibility, for In cooling the
tR,ei% material for lenses. The other IS &c 70 SS set rid
, Of chords d., int IN the g, glass ;hs s Which mor rsqsSires q very
rarely CIV r attained.
"Guinand's process is essentially as follows:
that the heat can be applied all around It and as as
it is technically called. is now Thoroughly
melted. requiring about thirty hours for perfect
l TeniIon At i ' sros ssISo i GfthG pa p5SffsifI sni ns%ri, in;
thorough stirring of the fluid mass. For this
purpose q s],iTr9r made o, itho, pqrcst
SO as not 10 chill tho glass. This %stirrenrs. called
be secured Inside Of the upper end of Il. tho long
handle of the iron part being carried in a shievc
on inc BlNe OF inc furnace 30 ms TO carry IFS
weight. The stlrrinR is continued for about
three hours. Then double covers arc placed
over the mouth Of the pot ard carefully luied
cgrcss OF air in the furnace is carefully scaled
and. the furnace, pot, and glass allowed TO cool
the weight of the melted mass and size Of the
furnace. The front Of the furnace is now taken
at its contents. The pot is usually found pretty
well shattered, and is, broken away from tho
now s%olidiicd and cooled mass within 1t. Tho
fp1n "a ia nlRn fpunH hrDEpn intn irrny r 1nn,n no
OF greater or less size. but ali are examined and
set inside for use according to their value.
covered by Guinand, a process Invaluable in tho
art of optical glass making. lump OF tho
lens is selected, all its impcrfections are ground
or cut away and then 1T !, is placed In q special
' o9 INC r IN Z n'oH dist or clay c OF the 81 di cIay
placed over tho mould to keep all flame
away from the glass and the temperature
tho glass may not crack. for ii it once cracks
il will DO ruined. As the temperature reaches
and gradually settles into the form Of the mould.
Whcn this Is accomplished the cooling process
and SSv during this II t time n from mu ,sh be ,o k .wtn oxcI n@Ssii
and other sources Of chills prevented or tho
mass will show Inequalities OF density which
After, the first annealing tho disk is ground
md polished on the faces. and again examined for
II imperfections such as strin. chords, or stones
arc found in the glass they must be ground out
process no Even then i The disk * has sasD NOT yet ctr passed sssed
through the entire gauntlet it must run before
being pronounced At for II great objective. All
OF their perfection. This doubling Thomas
now repolishcs the surfaces ana with his polari-
has not been regular tho ~tell-tale pc.
has no mercy. but picks out the de-
this ordeal, It must then be 'ssaabjecttccd to p. care are
ful study for STRIFE and unequal density.
TO locate stri@. II they exist. . beam
inch of which is carefully studied; the keen eye
or chords that would do harm. Unequal density |
is a far moro difficult thing to deteci, and unless
4, ,ti rs Of "a a pro character &c a Something un.
ijngl. 1t cannot be detected until the objective
has passed the stage of grinding and polishing.
thrown away on a bad piece Of glass because of
unequal density, which could be discovered only
when the lens was nearly complete.
Tho elder Guinand uicd In 1923. His son.
Inc associate OF Bontemps, die in 1851. and
for many OF the larger Telescopes Of modern
ines including those for The great Lick objec-
snme h As s the ssath % # M II; Psii: M Ms M Sad @6 be,
success in making glass for obiec- |
lives Of the largest size; for not only did he sue
telescope objective. but. has recently succeeded
In making a pair of 45-inch disks for the great
The Paris Exposition Of 1900.
Attempts have been made to manufacture
1 nS glass Il nth this ,o country with quite %fetter.
s. Co. established an optical glass factory
n connection with their large works ut FL
gas for fuel. Mr.. Fell. son OF tho celebrated
,rcnch optical glass maker. was engaged by
ir. Macbeth to super!ntend the work. AZ
er many costly experiments aud many
l!scouragements this firm succeeded in
md remarkable fine quality Of annealing. The
2.inch disk for the Photographic correcting lens
u the Dudley obseryatory was made from glass
mailer disks ha re also been worked from it by
opticians for various institutions Of
Mr.. Macbeth has also succeeded in
a pair OF crown and flint disks. %
inches In diameter, of very great excellence"