425 
1910-11.] Energy in Torsionaily Oscillating AVires. 
the interval which elapses after starting the experiment until the first 
reading is taken. A rough idea of the value of a to be taken is got from 
the curve with scale readings as ordinates and number of oscillations as 
abscissae, when the distance from the y axis of the line which the curve 
approaches asymptotically gives the value of a. If a wrong value of a be 
taken, the points in the curve of log y against log ( x-\-a ) will not lie in a 
•80 *90 (Logy) 1-0 1-1 
straight line, a curve convex to the origin being obtained if the value of a 
be too large, and a curve concave to the origin it the value of a be too small. 
This is seen* to be the case in diagram 1, when with a — 90 the curve is 
concave, and with a = 110, convex. The value of a which gives the straightest 
line is taken, and from the tangent of the angle included by the line and 
the axis along which log y is measured n is found, and b can then be got 
by substitution. 
* The scale readings y on the diagrams correspond to a rotation through 1° per T75 cm. 
of scale. 
