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DRYING CAVITIES. 153
of a small blowpipe with a cylinder an inch long,
and half an inch in diameter ; this is placed down
within two inches of the point of the instrument.
Fig. 43.
This cylinder is either made of very heavy metal, or
rilled with wire or something that will retain heat
on the other end is attached a stiff India-rubber ball
with an eyelet opening one-fourth inch in diameter.
By placing the thumb upon this opening, and making
compression, a jet of air is forced through the point
of the pipe, and the cylinder being previously heated,
the temperature of the jet will be governed by that
of the cylinder, and the velocity with which it is
forced through the instrument. This jet thrown
into a cavity that has been made as dry as possible
by wiping, soon makes a very perceptible change, the
walls becoming whiter than before. This we con-
sider the most desirable condition in respect to dry-
ness, that can be obtained.
DRYING CAVITIES. 153
of a small blowpipe with a cylinder an inch long,
and half an inch in diameter ; this is placed down
within two inches of the point of the instrument.
Fig. 43.
This cylinder is either made of very heavy metal, or
rilled with wire or something that will retain heat
on the other end is attached a stiff India-rubber ball
with an eyelet opening one-fourth inch in diameter.
By placing the thumb upon this opening, and making
compression, a jet of air is forced through the point
of the pipe, and the cylinder being previously heated,
the temperature of the jet will be governed by that
of the cylinder, and the velocity with which it is
forced through the instrument. This jet thrown
into a cavity that has been made as dry as possible
by wiping, soon makes a very perceptible change, the
walls becoming whiter than before. This we con-
sider the most desirable condition in respect to dry-
ness, that can be obtained.
