deviation
from the vertical in their zig-zag descent, as in Fig. 15. Thus, the
majority of favoured situations in this mine are situated on the
foot-walls of a part of the fracture, somewhat as in Fig. 16. As the
rocks dip at a flatter angle than on other parts of the field, these
fractures also are more nearly horizontal, though, as usual, they are
not-parallel to the dip of the strata. In consequence of the greater
twist effects to the field here, they run more diagonally to the strike
of the rock layers.
The
general pitch of the lines of favoured situations agrees more with the
line of, and pitch of, the main obstructions to the downward movement
of the water than with the exact pitch of the strike of the rocks; but