440 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XXVIII. — An Apparatus for inducing Fatigue in Wires by means of 
repeated Extensional and Rotational Strains, with the Effects 
produced by such Fatigue in the Laws of Torsional Oscilla- 
tion. By J. B. Ritchie, B.Sc., Carnegie Research Scholar in Physics, 
University College, Dundee. Communicated by Prof. W. Peddie. 
(MS. received March 6, 1911. Read same date.) 
In the preceding paper the law of torsional oscillation 
y n (x + a) = b, 
where y — range of oscillation, x = number of oscillations since start of ex- 
periment, and n, a, b constants for any one experiment, is considered with 
reference to wires of various materials, together with the effects produced on 
the constants of that empirical equation, and in particular on the constant n, 
by altering the initial conditions of the experiment. The wires were subjected 
to changes of length, diameter, temperature, and rigidity, and the resultant 
changes in the values of n, a, and b were given in detail. It was noted that 
the application of a large extensional force had a great effect in some cases, 
notably in the case of several of the metals after having been raised to a red 
heat in the electric furnace. The present work was undertaken to find the 
effect produced by a repeated application of an extensional force and by a 
repeated application of a twist to one end of the wire, the other end being 
held firm, thus tending to induce fatigue in the wires, the supposition 
being that such treatment would have an effect in the mode of oscillation 
when tested immediately afterwards. The latter step is necessary since it 
has been shown (Peddie, Trans. Roy. Soc. Edin., vol. xxxix., 1897-1898) 
that rapid partial recovery from fatigue is possible. 
The apparatus used for imparting these continued strains is a modifi- 
cation of an earlier machine used by Dr Peddie in these investigations, and 
was designed by him, the cost of construction being defrayed by means of a 
Royal Society grant given for the purpose. 
The accompanying photograph shows the complete apparatus, with the 
battery and rheostat introduced into the circuit, but unfortunately the wires, 
which are in position for being fatigued, are not evident. The various parts 
of the apparatus will be seen to better advantage in the following diagram, 
and the description will be facilitated by the use of the various letters. 
The whole apparatus is supported by a three-legged table, in height 4J 
