The writer thinks it is unfortunate that the author has not had an opportunity of visiting with him many trenches in which no break had occurred, and yet in which the bracing had to be strengthened continually near the top. This was especially true of a horizontally sheeted and braced shaft of large area. The writer believes that it is not out of place to express the hope that the author may still change his viewpoint, and may eventually regard only as phenomena well-braced trenches which in sand or gravel do not show evidences of heavier pressure near the top.
Referring now to tunnel pressures, the author [states]:
“If there was no settlement of the earth,
, in relation to
, * * * but, as most of the weight of
is carried by the sides, in case of sufficient settlement, the vertical unit pressure,
