ABSTRACT
The problem of the nature of emission and absorption of radiation has occupied a very prominent position in modern Physics, both on account of its outstanding importance and of the great difficulties involved. It is clear that the question of the excitation of X rays and their conversion into β rays, and also the spontaneous emission of β and γ rays from radioactive substances, must be included in any general theory of radiation. During the last few years a number of careful investigations have been made in this Laboratory bearing on this problem, and it may prove of interest to discuss briefly the evidence that has so far been obtained and to indicate the general conclusions that can be drawn from it. The problem is much too large and involved to hope for an immediate and definite solution, but the experimental results are sufficiently complete to afford some data for drawing some tentative conclusions.
