place so as to bring the particles into closer contact, and in such a
way that the internal stresses are practically those only of
compression, and the shearing stresses are within the limits possible
for the material in question.

The author has repeatedly made assumptions which are not borne out by
the application of his mathematical formulas to actual extreme
conditions. This method of application to limiting conditions is
concededly sometimes faulty; but the writer believes that no earth
pressure theory, or one concerning arch action, can be considered as
satisfactory which does not apply equally well to hydraulic pressure
problems when the proper assumptions are made as to the factors for
friction, cohesion, etc. For example, when the angle of repose is
considered as zero, in the author's first formula for _W_{1}_, the value
becomes ½ _W_{1}_, whereas it should depend solely on the depth, which
does not enter the formula, and not at all on the width of opening, _l_,
which is thus included.

The author has given no experiments to prove his statement that "the
arch thrust is greater in dryer sand," and the accuracy of the statement
is questioned. Again, no reason is apparent for assuming the direction
of the "rakers" in Fig. 3 as that of the angle of repose. The writer
cannot see why that particular angle is repeatedly used, when almost any
other would give results of a similar kind. The author has made no
experiments which show any connection between the angle of repose, as he
interprets it, and the lines of arch action which he assumes to exist.

With regard to the illustration of the condition which is thought to
exist when the "material is composed of large bowling balls," supposedly
all of the same size, the writer believes the conclusion to be