sistance is insufficient, they
continue to increase in measure as the pressure is further prolonged,
and at every increase in permanent capacity, their resistance
diminishes.

[Illustration: Fig. 1.--MACHINE FOR TESTING BOTTLES.]

The apparatus shown in Fig. 1 is called an elasticimeter, and permits
of a preliminary testing of bottles. The bottle to be tested is put
into the receptacle, A B, which is kept full of water, and when it has
become full, its neck is played between the jaws of the clamp, _p_.
Upon turning the hand wheel, L, the bottle and the receptacle that
holds it are lifted, and the mouth of the bottle presses against a
rubber disk fixed under the support, C D. The pressure of the neck of
the bottle against this disk is such that the closing is absolutely
hermetical. The support, C D, contains an aperture which allows the
interior of the bottle to communicate with a glass tube, _a b_, which
thus forms a prolongation of the neck of the bottle. This tube is very
narrow and is divided into fiftieths of a cubic centimeter. A
microscope, _m_, fixed in front of the tube, magnifies the divisions,
and allows the position of the level of the water to be ascertained to
within about a millionth of a cubic centimeter.

A force and suction pump, P, sucks in air through the tube, _t_, and
compresses it through the tube, _t'_, in the copper tube, T, which
communicates with the glass tube, _a b_, after passing through the
pressure gauge, M. This pump, then, compresses the air in the bottle,
and the gauge accurately measures its pressure.

To make a test, after the bottle full of water has been fastened under
the support, C D, the cock, _s_, is opened and the liquid with which
the small reservoir, R, has been filled flows through an aperture above
the mouth of the bottle and rises in the tube, _a b_. When its level
reaches the division, O, the cock, _s_, is closed. The bottle and its
prolongation, _a b_, are now exactly full of water without any air
bubbles.

The pump is actuated, and, in measure as the pressure rises, the level
of the liquid in the tube, _a b_, is seen to descend. This descent
measures the expansion or flexion of the bottle as well as the
compression of the water itself. When the pressure is judged to be
sufficient, the button, _n_, is turned, and the air compressed by the
pump finding an exit, the needle of the pressure gauge will be seen to
redescend and the level of the tube, _a b_, to rise.

I