364 GROOM : EFFECT OF FAULTS ON CHARACTER OF SEASHORE. 
parallel to the fault, and extending to a distauce of a foot or several 
feet from the fault, can be detected. In the larger dislocations large 
blocks of limestone or shale may be broken off and jammed up at 
various angles, together with more triturated material, between the 
lips of the fault. The portion of rock mechanically affected has not 
the appearance of being greatly altered chemically, but the shear and 
fault planes, which generally cross the bedding and joint planes at an 
angle, have divided up the rock into a mass of rhombohedral or 
irregularly-shaped fragments, forming a kind of loose breccia lining 
the sides of the fault, the fragments of which, however, have not been 
cemented together by subsequent infiltration into a hard rock. This 
material is accordingly easdy removed by the waves, and thus 
channels are eroded along lines of faulting. The fractured margins 
of even the most important faults, however, do not generally extend 
to more than a foot or so from the fault itself, so that though 
mechanical disruption greatly aids the denudation of the fault in a 
vertical direction, the widening must be accomplished mainly by the 
abrading action of the sea-water. 
Where two faults meet, or are only at a short distance apart, 
still more of the rock may be removed, and in this way permanent 
pools, or v-shaped inlets are produced. 
Prof. T. McKenny Hughes, whose experience of field geology 
is well-known, informs me that he has observed many facts similar to 
those described above. He says — " I have seen many cases quite con- 
firmatory of the view you maintain. Along the coast S. and W. of Tor- 
quay for instance there are many examples, and also round Ilfracombe. 
Some good examples may be seen on the coasts of Cardiganshire, 
south of Aberystwith. But better still are seen on the south coast 
of the Isle of Man. There are some on the shelving limestone shore 
at Biarritz. Cases of weathering along joints are as well illustrated 
in the Lower Greensand at Hunstanton as anywhere. The rock 
perishes along the joints, and large portions disappear altogether, 
leaving a series of cushions of rock, delightful to small boys, who 
jump from one to the other with leaping poles. From the cliff above 
these are seen to be only the more weathered portions of the jointed 
rock that forms the whole shore. The Clints or bare limestone 
