ABSTRACT
The scientist are indebted to Metropolitan Vickers for the great care taken in the construction of the electromagnet, which has proved admirable for its purpose; and for the presentation to us of one of their oil diffusion pumps to obtain the necessary high vacuum in the interior of the magnet. The time constant of the circuit formed in this way is of the order of one second, and any sudden changes in the external circuit produce relatively slow changes in the current through the magnet and mutual inductance. Thorium C- Experiments to be undertaken were chosen so that the results obtained would be of interest even if the accuracy of measurement were no. as great as it is hoped ultimately to attain. It has been found that the differences of energy between the main group and two of the long range groups from radium C', deduced from measurements, are in close accord with the energies of γ-rays found by Ellis.
