and the atoms of lead and other permeable substances be absolutely zero or small enough to allow the known permeation. Taking next the a radiation, the apparent great absorption of the vitreous electric emanation from radium was only apparent. It meant that an atom shot from radium with less than its neutralizing quantum of electrons could not go far through a solid or liquid without acquiring the neutralizing quantum. The β absorption might be regarded as probably real. Atoms of resinous electricity shot from radium could not be expected to enter a screen of metal, glass, or wood, or liquid, and leave at the other side, irrespectively of the insulation of the screen and of the radium. The full consideration and experimental investigation of the emission of atoms of resinous electricity from radium hermetically sealed in a glass bulb or tube led to surprising and interesting results. As to the γ rays, there was no difficulty in supposing that non-electrified vapour of radium passed very freely through metals or glass without any electric disturbance. It had been published that loss of weight in the course of a few months had been proved. Returning to Becquerel's original discovery in respect to uranium—the electric conductivity induced in air and other gases by a radio-active substance there was a ready explanation in the resuscitation of the old doctrine of Æpinus. The ordinary thermal motions within any solid, liquid, or gas must cause occasional shootings out of electrons from the substance,
