The experiments of Roentgen, § 90, seem to show that the discharging effect of X-rays is due to the air through which the rays have passed. It is certain that the discharge of electrified bodies by light occurs more generally for negatively than for positively charged bodies, § § 99_B_, 99_I_, and 99_S_, that it depends upon the nature, § 97_b_, and density, § 97_a_, of the gas surrounding the body, and also upon the material of the charged body itself. § 98. The discharge would, therefore, seem to be connected with a chemical action, § 153, _near end_, which is promoted by the rays. This seems all the more probable, since it was found, § 98, that the more electro-positive the metal, the longer the wave length that would influence the discharge. In this connection, it is well to note that Tesla found, § 146_a_, that in their power of reflecting (or diffusing X-rays), the different metals stand in the same order as in the electric contact series in air, the most electro-positive being the best reflectors. It would be interesting to know whether connecting the reflecting plate to earth, would, in any way, vary its reflecting power. The X-rays seem to discharge some bodies, when positively charged, and other bodies when negatively charged. They will also give to some bodies a positive, and to others a negative charge (§ 90_c_). Is the order here also that of the electrical contact series in air? Are not all the phenomena of electrical charge and discharge, of reflection or diffusion, and of X-rays, connected with chemical action, as the apparent difference of potential, due to contact, undoubtedly is? § 153. An experiment by La Fay (§ 139_a_) seems to show that X-rays, in air, after passing through a charged silver leaf, acquire the property of being deflected by a magnet, as are the cathode rays inside the generating or exhausted observing tube, § 72_a_. If this is confirmed, it would go far to support the theory that these rays are streams of _something_. [Illustration: FROM SCIAGRAPH OF HEAD BY PROF. GOODSPEED. NASAL BONES APPEAR LIKE EYELASHES. _Inter. Med. Mag._, June, ’96. The cervical vertebræ are distinguishable in the original, but barely so in the half-tone. Fillings are located. ] The burden of proof, up to the present, seems to be against any wave theory of the X-rays, for, although they are like the ultra-violet rays in producing fluorescence and in affecting the photographic plate, and have some points of similarity to these rays in their effect upon charged bodies, the X-rays are totally unlike the ultra-violet, in respect to diffraction and interference phenomena. In fact, the absence of such phenomena, if they are really absent, is conclusive proof that the X-rays cannot be wave motions, unless of a wave length extremely short even as compared to waves of light.