WE took a Glaſs Helmet or Alem
bick (delineated by the ſeventh
Figure) ſuch as Chymiſts uſe in Diſtilla
tions, and containing by conjecture be
tween two and three Pints: The Roſtrum
or Noſe of it mark'd with (c) was Herme
tically cloſed; and at the top of it was a
hole, into which was fitted and cemented
one of the Shanks of a middle-ſiz'd Stop
cock; ſo that the Glaſs being turn'd up
ſide-down, the wide Orifice (which in
common Glaſs-Helmets is the onely one)
was upwards; and to that wide Orifice
was fitted a caſt-Cover of Lead, which
was carefully cemented on to the Glaſs:
Then the other Shank of the Stop-cock
being with Cement likewiſe faſten'd into
the upper part of the Pump, the exſucti
on of the Air was endeavoured. But it
was not long before, the remaining Air
being made much too weak to ballance
the preſſure of the ambient Air, the Glaſs
was not without a great noiſe crack'd al
moſt half round, along that part of it
where it began to bend inwards: As if
in the Figure the crack had been made ac
cording to the Line (ab); and upon an
bick (delineated by the ſeventh
Figure) ſuch as Chymiſts uſe in Diſtilla
tions, and containing by conjecture be
tween two and three Pints: The Roſtrum
or Noſe of it mark'd with (c) was Herme
tically cloſed; and at the top of it was a
hole, into which was fitted and cemented
one of the Shanks of a middle-ſiz'd Stop
cock; ſo that the Glaſs being turn'd up
ſide-down, the wide Orifice (which in
common Glaſs-Helmets is the onely one)
was upwards; and to that wide Orifice
was fitted a caſt-Cover of Lead, which
was carefully cemented on to the Glaſs:
Then the other Shank of the Stop-cock
being with Cement likewiſe faſten'd into
the upper part of the Pump, the exſucti
on of the Air was endeavoured. But it
was not long before, the remaining Air
being made much too weak to ballance
the preſſure of the ambient Air, the Glaſs
was not without a great noiſe crack'd al
moſt half round, along that part of it
where it began to bend inwards: As if
in the Figure the crack had been made ac
cording to the Line (ab); and upon an
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