[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. If the glass of the bottle has undergone no permanent deformation, the level will rise exactly to the zero mark, and denote that the bottle has supported the test without any modification of its structure. But if, on the contrary, the level does not return to the zero mark, the limit of the glass's elasticity has been extended, its molecules have taken on a new state of equilibrium, and its resistance has diminished, and, even if it has not broken, it is absolutely certain that it has lost its former resistance and that it presents no particular guarantee of strength.