The above tests were made by Albert Buquet and Albert Gascard, at the Cabinet de Physique de l’École des Sciences de Rouen. The half-tone on lower half of adjacent page, 164, was taken from a sciagraph by Prof. Dayton C. Miller, of Case School of Applied Science. The differences of opacity are proved, because all were of same thickness and exposed simultaneously. Prof. Sylvanus P. Thompson (_The Elect._, Lon., May 18, ’96) confirmed the above, and also found that, although the diamond is more transparent than glass, it is more opaque than block carbon or graphite. Mineralogists are thus enabled to submit minerals to the X-ray test in making analyses. 157. DUFOUR’S EXPERIMENT. INACTIVE DISCHARGE TUBES MADE LUMINOUS BY X-RAYS. _Comptes Rendus_, Feb. 24, ’96. From trans. by Mr. Pignolet.—He observed that very small and sensitive Geissler tubes phosphoresced when exposed to X-rays. § § 22, 23. 158. BEAULARD’S EXPERIMENTS. NON-REFRACTION OF X-RAYS IN A VACUUM. _Comptes Rendus_, Mar. 30, ’96. From trans. by Louis M. Pignolet. With prisms of ebonite, F. Beaulard held that no decided deviation could be observed within the vacuum. 159. CARPENTIER’S EXPERIMENT. SCIAGRAPH SHOWING THE PARTS IN RELIEF ON A COIN. _Comptes Rendus_, Mar. 2, ’96. From trans. by Louis M. Pignolet. An imprint of a coin stamped upon a thin piece of well annealed aluminum by pressing the coin against the aluminum, was reproduced in a sciagraph. The raised parts of the coin were scarcely 8/100 of a millimeter high. The aluminum was 5/10 millimeter thick. This result is admirably represented by the sciagraph of an aluminum medal on page 166, taken by Prof. Dayton C. Miller, of Case School of Applied Science, _Elect. World_, N.Y., Mar. 21, ’96, who also made a sciagraph of a copper plate 1/4 inch thick having blow holes which appeared in the picture, but they could not be detected by light, serving to illustrate an application of the new discovery in testing the homogeneity of metals. 160. WUILLOMENET’S EXPERIMENTS. TRANSPARENCY OF THE EYE TO THE X-RAYS DETERMINED BY SCIAGRAPH OF BULLET THEREIN. _Comptes Rendus_, Mar. 23, ’96. A sciagraph taken with an exposure of _three hours_ showed perfectly a lead shot introduced into the vitreous media of the eye of a full grown rabbit. Therefore the opacity of the media of the eye was not absolute. In a second series of experiments by Dr. Wuillomenet a human head was used, but the results were negative in spite of a great intensity of the rays and a long exposure, § 82. 161. FERNAND RANWEZ’S EXPERIMENTS. APPLICATION OF THE X-RAYS TO ANALYSIS OF VEGETABLE MATTER. _Comptes Rendus_, Apr. 13, ’96. From trans. by Louis M. Pignolet. Sciagraphy can render valuable services in analytical researches and specially in the analysis of vegetable foods where they will show the most usual adulterations consisting of mineral substances. [Illustration: BAS-RELIEF SCIAGRAPH, § 159, BY PROF. DAYTON C. MILLER. ]