Year: 1875

The Wonderful Discovery of n GInss Manu-


facturcr, as Illustrated before n New


York Audience.


Prof. Thomas Egleston, Of the New
York Columbia College school of mines,
presented an account of the remarkable
La Bastie process for toughening glass,
so as to render it incapable of breaking,
before the Academy of Sciences. He
said that, during last autumn, NJ. La
Bastie, having made O number of ex-
periments in making glass (being con-
nected with glass manufacturing, sue
ceeded i'll making it as tough as cast
iron. He does this by heating ordinary
glass to red heat and plunging it into
bath of fatty material, the composition
OF which he has not disclosed. Prof.
Egleston then threw number of speci-
mems of the tempered glass, several
being watch crystals, and equally thin
pieces, in the air. They fell on the floor
with metallic clang, and rebounded to
the height of several inches. Some of
these pieces were ordinary looking watch
crystals. After showing the strength of
the specimens i'll this way, Prof. Egle-
ston threw plate in the air, and after
several attempts succeeded in breaking
1t. He then detailed large number of
experiments which had been made by
him on the glass with reference to its
capacity for withstanding shock, its re-
sistance of heat, and its chemical
strength as compared with ordinary
glass. With regard to shock he had had
number of steel missiles made, of two,
four, six, eight, and sixteen ounces
weight, which were allowed to fall from
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pared glass. He had done this because
he found that none of the shocks usually
applied to test glass would break this.
The missiles were carefully prepared, so
that their edges would not be dented,
thus preventing the waste of any OF the
force Cf the collision on the missile it
self. From nearly one hundred expert
ments he found that ordinary one and a
quarter inch glass always broke under a
blow from n missile falling thirteen
inches, while the tempered never broke
under e fall of less than five feet. A
two ounce missile was dropped from
different heights, increasing by three
inches up to thirteen feet, and the pre-
pared glass withstood these shocks.


A test was then applied for suspending
weights. A piece of ordinary glass g. 7
inches wide and .27 inch thick, general
ly broke under a weight of fifteen or
sixteen pounds, although one piece
stood weight of thirty seven pounds,
while similar piece of the prepared
glass stood over one hundred pounds
without breaking. A long series of ex-
perlments was then made in glass made
for vault lights, and the tempered glass
n quarter of an inch thick was round to
be superior to n piece of ordinary COM
'mercial glass an inch and half thick.
First the weights were so applied as to
bring the test on knife-edge balance or
n mathematical line. A piece of ordi-
nary glass broke under fifty -four pounds,
while similar piece of the tempered
only broke at pressure of one hundred
and fifty-five pounds. When the weight
was distributed over q width of two and
n half OF three inches ordinary glass
broke ut from fifty to sixty pounds,
while the tempered stood test of two
hundred and ten pounds, and, in one in
stance, the weight was piled on until the
support of the platform on which the
experiment was being conducted gave
way, and the platform broke down,
while the glass remained unbroken.


The strength of the glass was not,
however, its most wonderful character
lstic. Its resistance to heat was also
marvellous. The temperature of differ
ent ordinary flames was first determined
by means of pyrometers constructed for
the purpose, and was found to be from
300 degrees to 1000 degrees, according
to the kind of flame. Two thousand
degrees was then directed on the center
OF plate of prepared glass. eighteen
inches square, until at the point of con-
tact with the flame the glass became red
hot. The hand could not then be borne
within three inches of the red hot por-
tion of the glass, yet the glass could be
comfortably handled if grasped four
inches from the red hot part. The first
plate was poor one, and broke after be-
ing subjected to this heat for three
minutes. The others were not broken
by it. 1t was found that the glass could
be safely cooled 100 degrees at q time,
but cooling it more rapidly broke it.
Ordinary glass stood such tests as these
only eight seconds. The application of
this was that if fire was started in a
room with windows of this glass, the
framework of the windows would burn
out and allow the glass to fall before q
draft would be created. Lamp shades
were then tested by using kerosene
lamps with q combination of Bunsen
burners, which threw blue fame
(showing that the carbon was all con-
sumed, making the heat intenee), along
the whole length of the tube and six or
seven inches beyond it. All kinds of
lamp chimneys known had been tried by
this test, and none were found that could
withstand it, The tempered chimneys
were then submitted to the test for half
an hour, and then cooled, and again
tried for half an hour. The consequence
was that the lime glass was somewhat
dis ,olored but not cracked. The lead
glass was blackened but not broken. and