: Commonwealth Shipping Committee
: 43.97 MB
6 December l911
.] distance equal to its depth would not meet the case, as in
some cases it would be unworkable, and in others would be dangerous. An
overburden consisting of strong clay near the top and looser material beneath,
would, when falling. shoot out over the slope formed by the loose material when
falling. and masses of the clay might roll
over the ledge and drop into the quarry.
A safer method would be to remove it. in steps or lifts, not exceeding, say, 6 or 8
feet in height, ...