232

FLUIDITY AND PLASTICITY

rather than orifices or very short tubes, for the flow of a plastic
material through an orifice gives no idea of the mobility of the
material, just as the flow of a liquid through an orifice is largely
independent of the viscosity of the liquid. Flow through an

1300

1200

1100

1000

900

800

700

600

500

400

SOO

200

100

•I = 15
I- =16

f-

L

I

L

7

i

I

v

7

7

1

V

7

0 10 20 30 40 50 60 70 80 90/ 100 110
FIG. 81.—Hydraulic flow of a plastic material after experiments of Simonis.
orifice does, however, lead to a knowledge of the friction constant
of the plastic substance, as proved by the experiments of Simonis
(1905).
Simonis used 40 g of Zettlitz earth with 100 g of water
to which were added successive portions of a dilute solution of