424 Proceedings of the Royal Society of Edinburgh. [Sess. 
XXVII.— 1 The Dissipation of Energy in Torsionally Oscillating Wires 
of Brass and other Materials, with the Effects produced on 
the Law of Torsional Oscillation by Change of Temperature, 
etc. By J. B. Ritchie, B.Sc., Carnegie Research Scholar in Physics, 
University College, Dundee. Communicated by Professor W. Peddie. 
(MS. received March 6, 1911. Read same date.) 
In the determination of the law of decrease of torsional oscillations of an 
iron wire, when the range of oscillation is large in comparison with the 
palpable limits of elasticity, an equation of the form 
y n (x + a) = b 
has been shown by Dr Peddie {Phil. Mag., July 1894) to give close repre- 
sentation of results where — 
y = the range of oscillation. 
x = the number of oscillations since the commencement of observations. 
n, a, b — quantities, constant for any one experiment, depending on the 
initial conditions of the experiment and the previous treatment 
of the wire. 
The present work has been undertaken to find if this equation can with 
equal accuracy be applied in the case of wires of brass and other materials, 
and to find the effect produced on the constants of this equation by altering 
the initial conditions of the wire by change of temperature and by fatigue 
induced in the wire by repeated extensional or torsional strains. 
Method of Calculating the Constants. 
The method described by Dr Peddie in a second paper on the same 
subject {Trans. P.S.E., 1896) was employed for the determination of the 
quantities n, a, and b. 
Since 
n log y + log {x + a) = log b , 
then if log {x-\-a) be plotted against log y, the corresponding points will 
lie on a straight line which intersects the axis along which log y is measured 
at an angle whose tangent is n, provided that the proper value of a be 
inserted. The actual value of this constant to be added to x depends upon 
