t be required in practice.

It is thus seen that both these conditions can be fulfilled with
practical illustrations; that is, for an angle of repose of 90 deg., that
material which has weight and no thrust, and for an angle of repose of
zero, that solid material which has thrust but no weight.

Mr. Goodrich says the author has given no experiments to prove his
statement that the arch thrust is greater in dryer sand. If Mr. Goodrich
will make the experiment partially described as Experiment No. 3, with
absolutely dry sand, and with moist sand, and on a scale large enough
to eliminate cohesion, he will probably find enough to convince him that
in this assumption the writer is correct. At the same time, the writer
has based his theory in this regard on facts which are not entirely
conclusive, and his mind is open as to what future experiments on a
large scale may develop. It is very probable, however, that an
analytical and practical examination of the English experiments noted on
pages 379 and 380, will be sufficient to develop this fact conclusively.

The writer is forced to conclude that some of the criticisms by Mr.
Goodrich result from a not too careful reading of the paper. For
instance, he states:

"'It is conceded' (line 2, p. 357, for example) when the writer,
for one, has not even conceded the accuracy of the assumptions."

A more careful reading would have shown Mr. Goodrich that this
concession was one of the writer's as to certain pressures against or on
tunnels, and, if Mr. Goodrich does not concede this, he is even more
radical than the writer.

And again:

"'Nor can anyone * * * doubt that the top timbers are stressed more
heavily than those at the bottom' is emphatically doubted and
earnestly denied by the writer."

It is unfortunate that Mr. Goodrich failed to make the complete
quotation, which reads:

"Nor can anyone, looking at Fig. 5, doubt," etc.

A glance at Fig. 5 will demonstrate that, under conditions there set
forth, the writer is probably correct in his assertion as relating to
that particular instance. Further:

"For instance, the author's well-known theory that the pressures
against retaining walls are a maximum at the top and decrease to
zero at the bottom, is in absolute contradiction to the results of
experiments conducted on a large scale by the writer on the new
reinforced concrete retaining wall near the St. George Ferr