The penetrating power of the γ-rays from radium C

The primary object of the present research was to kind out if there is any residual radiation from radium C after theγ -rays of ordinary penetrating power have been entirely absorbed. In the course of the word it was necessary to measure the adsorption of theγ -rays by mercury. This, also, has therefore been investigated in some detail. Only experimental results are given in this paper. A discussion of the theoretical meaning of the results will be given in a subsequent paper dealing with hardening and scattering ofγ -rays. A very penetrating radiation may be looked upon either as a new type of radiation, resembling theγ -ray in that it is uncharged, but possessing a much greater penetrating power, or, if the assumption be made that theγ -rays are heterogeneous, as the most penetrating constituents of theγ -ray beam. The recent word of Danysz has shown clearly that some of theβ -rays from radium C are ejected with a velocity not less than 99 per cent, of that of light. It is not unreasonable to expect that there areγ -rays corresponding to these, and possessing, therefore, a much greater penetrating power than the average penetrating power of ordinaryγ -rays. This radiation, if it exists, would be present in theγ -ray beam only in very small amount, and detectable, therefore, only when a large source of radium is used, and special precautions taken.