particles of sand and surrounding water unless there is a tendency of
the latter to move; and that water in motion does not exert pressures
equal to those produced when in a static condition, the reduction being
proportional to the velocity of flow.

The author's conclusion (p. 371), that "pressure will cause the
quicksand to set up hydraulic action," does not seem to have been
demonstrated by his experiments, but to be only his theory. In this
instance, the results of the writer's experiments are contrary to the
author's theory and conclusion.

The writer will heartily add his protest to that of the author "against
considering semi-aqueous masses, such as soupy sands, soft concrete,
etc., as exerting hydrostatic pressure due to their weight in bulk,
instead of to the specific gravity of the basic liquid." Again,
similarly hearty concurrence is given to the author's statement:

"If the solid material in any liquid is agitated, so that it is
virtually in suspension, it cannot add to the pressure, and if
allowed to subside it acts as a solid, independently of the water
contained with it, although the water may change somewhat the
properties of the material, by increasing or changing its cohesion,
angle of repose, etc."

On the other hand, it is believed that the author's statement, as to
"the tendency of marbles to arch," a few lines above the one last
quoted, should be qualified by the addition of the words, "only when a
certain amount of deflection has taken place so as to bring the arch
into action." Again, on the following page, a somewhat similar
qualification should be added to the sentence referring to the soft clay