compressed air, and the latter will assume its normal volume again, and press in the liquid beneath it. If the quantity of compressed air is considerable, there will occur an expulsion, not only of the entire liquid, but also of the excess of air. [Illustration: Fig. 1.--HERON'S CUPPING GLASS.] The valve of which I have spoken is constructed as follows (Fig. 2, 1 _bis_ and 1 _ter_): Take two pieces of brass about one inch square, and about as thick as a carpenter's rule, and rub their surfaces against each other with emery, that is to say, polish them so that neither air nor liquid can pass between them. In the middle of one of the pieces bore a circular aperture about 4/10 an inch in diameter. Then fitting the two plates together by one of their edges, unite them by a hinge so that the polished surfaces shall coincide with each other. When this valve is to be made use of, the part containing the aperture is adapted to the aperture that is designed for the introduction of the liquid or air that is to be compressed. The pressure causes the other part of the valve (which moves easily on its hinge) to open and allow the liquid or air to enter the tight vessel, wherein it is afterward confined and presses against the unperforated part of the valve and thus closes the aperture through which the air entered."--_A. de Rochas, in La Nature_. [Illustration: Fig. 2.--HERON'S FOUNTAIN.] * * * * * PROFESSOR ADOLF MEYER has been experimenting upon the relative digestibility of natural and artificial butter. The experiments were made on a man of 39, and a boy of 9 years. He found that there was but little difference, but in these individuals the natural butter seemed to be more easily digested. While natural butter was all digested, at least 98 per cent. of the artificial butter was also digested.--_Chemiker Zeit_. * * * * * FILTH DISEASES IN RURAL DISTRICTS. By ALFRED L. CARROLL, M.D., NEW BRIGHTON, N. Y.