V. The action of light on selenium

The paper contains an account of a series of experiments which have been carried on during the past year, and which have had for their object the investigation of the electrical behaviour of selenium, especially as regards its sensitiveness to light. The first part contains a short summary of the results obtained by Professor Adams, which have been communicated to the Society. It has been already shown that the action is due principally, if not entirely, to those rays of the spectrum which are luminous, and that the ultra-red or the ultra-violet rays have little or no effect; also that the intensity of the action depends on the illuminating power of the light, being directly as the square root of that illuminating power.