in the very region where the cathode rays are generated, and that they travel in the reverse direction and precipitate themselves on to the cathode.” He verified this corollary by means of a modified feature of the apparatus shown in Fig. 2. The construction was the same except that there was a diaphragm having a perforation β´ within the protecting cylinder and opposite the smaller cylinder exactly as indicated, so that the positive electricity which had entered through β could only act on the cylinder A, B, C, D, by traversing also the hole β´. “When N was the cathode, the rays emitted traversed the two apertures at β and β´ without any difficulty, and caused the gold leaves of the electroscope to diverge widely. But when the protecting cylinder was the cathode, the positive flux, which, as was shown by a previous experiment, enters by the aperture β, did not succeed in separating the gold leaves, except at very low pressures. If we substitute an electrometer for the electroscope we shall see that the action of the positive flux is real, but that it is very small and increases as the pressure decreases.” [Illustration: FIG. 2. ] He inferred that: “These results, taken as a whole, do not appear to be easily reconcilable with the theory that the cathode rays are ultra-violet light. On the contrary, they support the theory that attributes these rays to radiant matter, § 54, near centre, a theory, which may at present, it seems to me, be enunciated as follows: In the vicinity of the cathode the electric field is sufficiently strong to tear asunder into _ions_ some of the molecules of the residual gas. The negative ions start off toward the region where the potential increases, acquire a considerable velocity, and form cathode rays; their electric charge, and consequently their mass (at the rate of one gramme equivalent per 100,000 coulombs) is easily measured. The positive ions move in the reverse direction; they form a diffused tuft, susceptible to magnetism, but are not a regular radiation.” 61_c_. ZEUGEN. _Comptes Rendus_, Jan. 27, 1896.—In a note regarding the experiments of Roentgen, called attention to his own communications to the Academie des Sciences in February and August 1886, describing his photographs of Mt. Blanc taken in the night by the invisible ultra-violet rays. This note is entered as many newspapers reported the photograph to be due to cathode rays, imagine the intense phosphorescence upon a screen at the top of the mountain, if such were the case.