AMPLIFICATION OF THE LAW OF POISEUILLE 53

the product of the pressure multiplied by the time of efflux to
be constant. The velocities ranged from 0.00011 to 0.00175
cm per second. From these experiments Glaser concluded that
" The velocity of efflux in this mixture is within very wide limits
without influence upon the magnitude of the viscosity." But
in experimenting with tubes of varying diameter, he obtained
remarkable results a part of which are given in Table XVIII.
We observe with Glaser that the fluidity rapidly falls off
as soon as the diameter falls below a certain limit. But this
limit depends upon the fluidity of the mixture, as was proved

f

0.5 1.0

Fadius of Tube

1.5

Fia. 18.—Eighty, eighty-five and ninety per cent mixtures of colophonium.
and turpentine give fluidities, multiplied by 10"~6, 10~~8 and 10~10 respectively,
which, vary with the radius of the tube. Such mixtures are apparently plastic
and do not obey the laws of viscous flow.

l!
II

by working in the same way with. 80 arid 90 per cent colopho-
nium mixtures, the true fluidities of which are approximately
2 X 10~~6 and 2 X 10~10 respectively. Since with smch rapidly
increasing values, the viscosities are inconvenient to plot, we
have changed his viscosities to fluidities. All of Ms values are
plotted in Fig. 18, using apparent fluidities as ordinates and
radii as abscissas. . We note that the points lie, for the most