304 The Viscosity of Pitch-like Substances. 
The authors entertained at one time the idea that the 
elastic viscous recovery might only be found to occur with 
substances which were mixtures; one constituent of which 
might be elastic and the other viscous. With the object of 
testing the matter some cylinders of sodium stearate were 
prepared. It was found that elastic viscous recovery occurred 
in this substance similar in every respect to that observed with 
such mixtures as glass or pitch. The viscosity of the substance 
is given in the general table. 
Shoemaker’s Wax. 
It was desirable that determinations of the viscosity of the 
same substance should be made by the method here described 
and also some other. It was found that shoemaker’s wax 
was, on the one hand, just sufficiently viscous to allow 
cylinders to be made from it for determination with the 
torsion method, and just sufficiently fluid to admit of its 
viscosity being determined by allowing a spherical body to 
drop through it. 
The mean value obtained by the torsional method working 
with two different-sized cylinders was w=4°7x10°. This 
value is open to considerable doubt, for cylinders of shoe- 
maker’s wax sag in the centre rather too quickly to give 
really reliable results, and would have to be supported by a 
fluid of the same density in the manner explained earlier in 
the paper. 
The Stokes method adopted for comparison gave very 
variable results. A steel bicycle-ball answered as the spherical 
body, the measurements of which showed it to be wonderfully 
true ; nevertheless it did not fall vertically, but irregularly 
from side to side in its descent. This may have been due to 
the ball rotating owing to lack of uniformity. The wax itself 
should have been fairly homogeneous, for it bad been poured 
when liquid into the containing cardboard cylinder. 
The position of the sphere was found from time to time by 
means of the X-rays. It took a fortnight to travel 1:8 em. 
The value for the coefficient of viscosity obtained varied 
from 6 x 1.0° to 23 x 10°, the mean value being about 10 x 10°. 
This is of the same order of magnitude as that obtained by the 
torsion method. This latter is probably too small because the 
sagging of the rod in the torsion experiment was so great that 
the torque could not be applied long enough to reach the 
“steady state. 
Observations were made with paraftin-wax and modelling- 
clay to ascertain the character of their behaviour. Paraffin- 
