Up: Glassmaking
Reminiscences
13 of 123
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"Place a tube, say two feet long, before a
fire in a horizontal position, having the position properly supported,
say by putting a cork at end end supported by pins for an axis; the
rod will acquire a rotary motion round the axis, and also a progressive
motion towards the fire, even if the supporters are declined from the
fire. When the progressive motion of the tube towards the fire is
stopped by any obstacle, the rotation is still continued. When the
tubes are placed in nearly an upright position, leaning to the right
hand, the motion will be from east to west; but if they lean to the
left hand, their motion will be from west to east; and the nearer they
are placed to an upright position the less will be their motion either
way. If the tubes be placed on a sheet of glass, instead of moving
towards the fire they will move from it, and about the axis in a contrary
direction from way they did before; nay, they will recede from the fire,
and move a little upwards when the plane inclines towards the fire."
Glass is used for
pendulums, as not being subject to affections
from heat or cold. It is, as is well known, a non-conductor. No metallic
condenser possesses an equal power
with one of glass. In summer, when moisture fails to collect
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