The Story of Pittsburgh
GLASS

5

HERE is scarcely a form of manufactured glass
in which Pittsburgh does not take the lead, from
window glass and lamp chimneys to optical glass
and astronomical lenses.

Very large is the city’s production of plate glass, window
 glass, pressed table ware and lamp chimneys. The
finer manufactures in glass are represented by establishments
 which make diffracting prisms, used in lighthouses,
lenses for telescopes, opera glasses, microscopes and rangefinders.
 Dr. John A. Brashear, who recently died, mourned
by thousands who knew him personally, and to whom he
was “Uncle John”, enjoyed an international reputation
as an astronomer and a maker of the finest telescopic
lenses made anywhere in the world. His establishment
was known the world over for the excellence of the lenses
it produced.

The Encyclopedia Americana, the most recently published
 work of this character, speaking of Pittsburgh, says:
“The total production of plate glass in the district in 1918
was nearly 60,000,000 square feet, which, if made into one
sheet, would cover an area of 1877 acres, or make a pane
of plate glass three miles high by one mile wide; and the
ordinary window glass made here, would, if in one piece,
oe a pane nearly three times as large.”
The invention of glass occurred at so early a date in
:he history of the world, as to be lost in obscurity. The
method of its discovery is a matter of surmise. Obsidian,
which is found in volcanic discharges, was the earliest form
of transparent matter. It was used by the ancient Egyptians
 in the manufacture of various objects. The Romans
and the early Mexicans also fashioned articles from obsidian.