absolutely unwarranted, and consequently the whole conclusion is
believed to be unjustified. Nor is the author's assumption (line 5, p.
361), that "the thrust * * * is measured by its weight divided by the
tangent of the * * * angle of repose" at all obvious.

The author presents some very interesting photographs showing the
natural surface slopes of various materials; but it is interesting to
note that he describes these slopes as having been produced by the
"continual slipping down of particles." The vast difference between
angles of repose produced in this manner by the rolling friction of
particles and the internal angles of friction, which must be used in all
earth-pressure investigations, has been repeatedly called to the
attention of engineers by the writer.[H]

The writer's experiments are entirely in accord with those of the author
in which the latter claims to demonstrate that "earth and water
pressures act independently of each other," and the writer is much
delighted that his own experiments have been thus confirmed.

In Experiment No. 3, the query is naturally suggested: "What would have
been the result if the nuts and washers had first been tightened and
water then added?" Although the writer has not tried the experiment, he
is rather inclined to the idea that the arch would have collapsed. With
regard to Experiment No. 5, there is to be noted an interesting
possibility of its application to the theoretical discussion of masonry
dams, in which films of water are assumed to exist beneath the structure
or in crevices or cracks of capillary dimensions. The writer has always
considered the assumptions made by many designing engineers as
unnecessarily conservative. In regard to the author's conclusions from
Experiment No. 6, it should be noted that no friction can exist between