152. THOMPSON’S (S. P.) EXPERIMENT. PENETRATING POWER OF X-RAYS VARIES WITH THE VACUUM. _Comptes Rendus._ CXIII., p. 809. _The Elect._, Lon., April 24, ’96, p. 866. In a communication to the Académie des Sciences Prof. Sylvanus P. Thompson of the University College of Liverpool, argued that by one kind of X-rays the bones of the hand were more easily penetrated than by another kind. The two varieties were produced by different vacua. § 75 and 76. Let the vacuum be supposed to become higher and higher. At the first generation of the X-rays, the fluorescent screen showed that the bones of the hand cast very dark shadows. With increase of the vacuum, the shadows of the bones were very faint. This result is also obtained by reduction of temperature. § 152_a_. 152_a_. BLEEKRODE’S EXPERIMENT. PERMEABILITY AT LOW TEMPERATURES INCREASED. _Elect. Rev._, Lon., June 12, ’96.—Experiments performed by him confirmed those of Edison. § 135. An experiment by Prof. Dewar strongly confirmed the results. They noticed the same peculiarity that Edison did, namely, that the shadow of the finger exhibited the flesh and bones as if they were equally transparent. Varied tests showed that the reduction of the temperature of glass increased its permeability. 153. MURRAY’S EXPERIMENT. REDUCTION OF THE CONTACT POTENTIAL OF METALS BY X-RAYS. _Trans. R. So._, Mar. 19, ’96. _The Elect._, Lon., Apr. 24, ’96, p. 857. J. R. E. Murray of the Cavendish Laboratory, at the suggestion of Prof. J. J. Thomson, carried on a long series of careful experiments, to find whether the contact potential of a pair of plates of different metals was, in any way, affected by the passage of X-rays between the plates. All the ordinary precautions were taken. The contact potential was measured by Thomson’s (Kelvin) method, see _Trans. Brit. Asso._, 1880. The important result obtained, was that “the air through which the rays pass, § 90, is temporarily converted into an electrolyte, § 47, and when in this condition forms a connection between the plates, which has the same properties as a drop of acidulated water, namely, it rapidly reduces the potential between the opposing surfaces of the plates to zero, and may even reverse it to a small extent.” 154. NODON’S EXPERIMENT. TRANSPARENCY OF DIFFERENTLY COLORED MEDIA TO THE X-RAYS. _Comptes Rendus_, Feb. 3, ’96. From trans. by Louis M. Pignolet. The rays were passed through two openings in a thick metal diaphragm, one of which was covered by an uncolored piece of gelatine and the other by a piece tinted with the color to be tested. The two images were received on the same plate. The various colors tested were traversed with equal facility by the rays, § 68 and 82. The investigation described above was made by Albert Nodon at the Laboratoire des Recherches Physiques à la Sorbonne.