101. THOMSON’S EXPERIMENT. MANIFOLDING BY X-RAYS.—If one desires to take a print of a negative, for example by means of sun-light, it is evident that, on account of the opacity of the photographic paper, only one sheet would be placed under the negative for receiving a print. However, the X-rays are so penetrating in their power that it is possible for them to produce sciagraphs through several sheets, and thereby to result in the production of several pictures of the same object with one exposure. Without an experiment to prove this, one might argue that the chemical action of one sheet would absorb all the energy. The experiment of Prof. Thomson shows that this is not so. The elements were arranged as follows: First a discharge tube; then an object, namely, a key escutcheon of iron; then yellow paper; then paste board; then black paper; then two layers of albumen or sensitized paper; then two célérité printing papers; then two platinum printing papers; then one célérité; then six layers of sensitive bromide paper; then four layers of heavy sensitive bromide paper (heavier); then three layers of black paper, and finally, at the maximum distance from the discharge-tube, a sensitive glass plate of dry gelatine, with its face up, thereby making twenty-five layers in the aggregate. It is interesting to notice that an induction coil was not employed, but a small Wimshurst machine, having connected to each pole a small Leyden jar. § 106. 1,200 discharges occurred during exposure. The results were as follows: No sciagraphs developed upon the albumen, célérité nor platinum, which, it should be noticed, were merely printing papers. § 128. The impressions on the ten bromide papers were weak. See Multiple Sciagraphs, Fig. 2, p. 94. He attributed the reason of this to the thinness of the film. Although the glass plate was furthest away from the discharge tube, yet the impression was greater than on any of the papers, the result being shown in Multiple Sciagraphs, Fig. 1, p. 94. He suggested that the plates for use with X-rays should have unusually thick films. Incidentally he found that the intensifying process could be employed with profit to bring out the small details distinctly. Dr. Lodge also recommended thick films. See _The Elect._, Lon., Apr. 24, ’96., p. 865. 101_a_. LUMIÈRE’S EXPERIMENT. ENORMOUS TRANSPARENCY OF SENSITIVE PHOTOGRAPHIC PAPER. _Comptes Rendus_, Feb. 17, ’96. Translated by Mr. Louis M. Pignolet.—With a ten-minutes exposure, objects were sciagraphed through 250 super-imposed sheets of gelatino-bromide of silver paper, to observe the absorption of the X-rays by the sensitive films. The one hundred and fiftieth sheet was found to have an impression.