ON CERTAIN ELASTIC PROPERTIES OF DRAWN 
TUNGSTEN WIRES. 
L. P. SIEG-. 
The Wires . — The wires used in these experiments were fur- 
nished through the kindness of Dr. A. G. Worthing of the Nela 
Laboratory of the General Electric Company, of Cleveland, 
Ohio. There were five specimens from each of two different sets 
of wires. Thus each group of five wires was drawn from the 
same original swaging. The wires range in radius from .002397 
cms. to .02584 cms. Tungsten is very hard and brittle, and can 
be drawn only by experts. The tungsten has previously to 
be made very free from impurities, and then worked and swaged 
into a rough wire. This is then drawn down while red hot 
through holes drilled in diamonds. Even after this apparently 
successful treatment, the wires show a tendency to fray and 
split when clamped. Thus their structure is far from uniform 
and homogeneous. 
The Apparatus . — The wires were used as suspensions of torsion 
pendulums, and the relations among period, amplitude, moment 
of inertia, radius of wire, etc., were determined. The coefficient 
of rigidity and the logarithmic decrement also were determined. 
The details of the apparatus, and the method of timing have 
previously been reported. 1 
Relation Between Period and Amplitude . — These wires were 
found to deviate from substances that obey Hooke’s Law in that 
the period was found to vary with the amplitude. In figure 28 
is shown the relation between these for a typical experiment. 
In the experiment represented by this curve the length of the 
wire was 25 cm., and its radius .0051 cm. The greatest ampli- 
tude chosen is seen to be only about 16° per cm. of length of 
the wire, and for so fine a wire this is not an excessive twist. In 
fact no appreciable shift of the zero took place. Further it was 
shown by separate experiments that the restoring torque was 
proportional to the torsion, even beyond the twist employed. So 
here is a case where Hooke’s Law holds statically, and yet kineti- 
cally there is a wide departure from it. The change in period 
1 Iowa Acad. Science, Proc. XVII, p. 185 : XVIII, p. 115 ; XIX, p. 189. 
