This method offers several advantages for small samples of the substances can be examined. The samples are not chemically changed. A great number of tests can be made in a short time. Lastly, the sciagraph obtained affords a permanent record. The tests were made on samples of adulterated saffron composed of mixtures of pure saffron and saffron coated with sulphate of barium. A sciagraph taken with an exposure of three minutes showed scarcely visible imprints of the pure but strong impressions of the adulterated. See sciagraph of pen, (mineral) in holder, (vegetable), in cut at upper part of p. 164, which also shows the graphite in a wooden pencil. 162. ERRERA’S EXPERIMENT. ACTION OF THE X-RAYS ON PHYCOMYCES. HERTZ WAVES AND ROENTGEN RAYS NOT IDENTICAL. _Comptes Rendus_, March 30, ’96. From trans. by Louis M. Pignolet.—_Phycomyces Nitens_, when submitted to the asymmetrical action of Hertz electric waves, became curved, according to Hegler. Errera found a Phycomyces was not affected by the X-rays, thus denoting an absence of Hertz waves in the rays. Credit for the above result is due to L. Errera, from experiments made at the Laboratoire Physique and the l’Institut Solvay (Université de Bruxelles). 163. GOSSART, CHEVALLIER, FOUTANA AND URUANNI’S EXPERIMENT, IN CONJUNCTION WITH J. R. RYDBERG. NO MECHANICAL ACTION OF X-RAYS. _Comptes Rendus_, Feb. 10, Mar. 23, Apr. 13, ’96. From trans. by Louis M. Pignolet.—The former party alleged that radiations from a discharge tube caused a cessation of the rotation of the vane of the radiometer. J. A. Rydberg was not inclined to confirm such action. A. Foutana and A. Uruanni made experiments and concluded that the action was due to an electro-static force, having noticed that a Leyden jar would also produce such effect. The author made some experiments to determine the matter in reference to X-rays at a distance outside of the electro-static field. The rays would neither stop the vanes nor cause them to rotate. He made some other experiments to detect whether there was any direct mechanical power possessed by the rays; but if any, it was exceedingly feeble. T. C. Porter made some experiments at Eton College, (_Nature_, June 18, ’96,) which confirmed the above results, finding that the radiometer is entirely inert to the Roentgen rays, whether they be from a properly electrically screened hot or cold tube. He distinguished between the caloric conditions, for he found that, not only will reduction of temperature vary the penetrating power of the rays, § 135 and 152_a_, but also will an increase of temperature.