﻿On Radioactive Transformations . 981 



angles so that Lissajous' figures are obtainable. PL XVI. 

 fig. 5 shows a loop o£ the string executing such a motion. 

 The effect of varying relative amplitude of the vibrations can 

 readily be traced in it. At the node of the transverse vibra- 

 tion the figure traced by a point on the string should be a 

 straight line : in the photograph it appears as a curve with a 

 convexity towards the fork ; this is clearly due to the 

 varying tension in the string caused by the large amplitude 

 of the fork, the string having been attached in this case at 

 the end of the prong. The curvatures of the figures at the 

 ventral segments on either side of the nodal line are in oppo- 

 site directions corresponding to the phase difference acquired 

 in passing through it. Perhaps the most interesting form ob- 

 tained by me in this way is that shown in PI. XVI. fig. 6, which 

 corresponds to a circular motion, with a simple harmonic 

 motion of double its period, and more than double its ampli- 

 tude superposed. The order in which the curve is traced is 

 easily made out from the photograph. 



To Professor Wilberforce are due my thanks for the great 

 interest he has taken in these experiments. 



George Holt Physics Laboratory, 



The University of Liverpool. 

 1st March, 1912. 



XCVIII. The Relation between the Ranges of a. Particles and 

 the Periods of Transformation of Radioactive Bodies. By 

 Prof. H. A. Wilson; F.R.S., F.R.S.C., McGill University, 

 Montreal *. 



IT has been shown recently by Geiger and Xuttall t that 

 there is an approximately linear relation between the 

 logarithms of the transformation constants (A,) of radioactive 

 substances and the logarithms of the ranges (d) of the 

 a particles which they emit. 



Radioactive transformations are somewhat analogous to 

 monomolecular chemical reactions, but are atomic in cha- 

 racter and independent of temperature. The kinetic energy 

 of the « rays may be regarded as a measure of a quantity 

 analogous to temperature which helps to determine the 

 internal state of the atom. This quantity may be called 

 the atomic temperature, and we may suppose that the rate 



*■ Communicated by the Author. 

 t Fhil. Mag. October 1911. 



