draulic press and
subjected to a sufficient pressure it will exhibit properties somewhat
similar to soft clay or quicksand under pressure. It will flow out of an
orifice or more than one orifice at the same pressure. This is due to
the fact that practically voids do not exist and that the pressure is so
great, compared with the molecular cohesion, that the latter is
virtually nullified. It is also theoretically true that solid stone
under infinitely high pressure may be liquefied. If in the cylinder of a
hydraulic press there be put a certain quantity of cobblestones, leaving
a clearance between the top of the stone and the piston, and if this
space, together with the voids, be filled with water and subjected to a
great pressure, the sides or the walls of the cylinder are acted on by
two pressures, one almost negligible, where they are in contact with the
stone, restraining the tendency of the stone to roll or slide outward,
and the other due to the pressure of the water over the area against
which there is no contact of stone. That this area of contact should be
deducted from the pressure area can be clearly shown by assuming another
cylinder with cross-sticks jammed into it, as shown in Fig. 10. A glance
at this figure will show that there is no aqueous pressure on the walls
of the cylinder with which the ends of the sticks come in contact and
the loss of the pressure against the walls due to this is equal to the
least sectional area of the stick or tube either at the point of contact
or intermediate thereto.

Following this reasoning, in Fig. 11 it is found that an equivalent area
may be deducted covering the least area of continuous contact of the
cobblestones, as shown along the dotted lines in the right half of the
figure. Returning, if, when the pressure is applied, an orifice be made
in the cylinder, the water will at once flow out under pressure,
allowing the piston to come in contact with the cobblestones. If the
flow of the water were controlled, so as to stop it at the point where
the stone and water are both under direct pressure, it would be found
that the pressures were totally independent of each other. The aqueous
pressure, for instance, would be equal at every point, while the
pressure on the stone would be through and along the lines of contact.
If this contact was reasonably well made and covered 40% of the area,
one would expect the stone, independently of the water, to stand 40% of
the pressure whi