[Illustration: Figs. 1. and 2.]
The little piece of apparatus shown in Fig. 1 was designed to furnish
a clear demonstration of the principle under consideration. It is
essentially an arrangement by which a downward pressure is applied to
a confined mass of air or water, and the resultant pressures measured
in the three directions, down, up, and sideways. By means of a broken
rat tail file kept wet with turpentine three holes are bored through a
bottle, one through the bottom, one through the side, and one through
the shoulder, as near the neck as may be convenient. The operation is
quick and easy, the only precaution to be observed being to work very
slowly and use but a slight pressure when the glass is nearly
perforated. The holes may be enlarged to any size required by careful
filing with the wet file. From each of the holes a rubber tube leads
to one of the glass manometer tubes at the right in the figure, the
joints being made air tight by slipping into each rubber tube a piece
of glass tubing about half an inch long in order to swell it to the
size of the hole it is to fit. The ends of these glass tubes must be
well rounded by partial fusion in a gas flame, that there may be no
sharp edges to cut the rubber. The bottle rests in a depression in the
turned wood base, the lower rubber tube passing out through a hole in
the wood.
Pages:
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124