parallel to the fault, and extending to a distance of a foot or several feet from the fault, can be detected. In the larger dislocatious 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 easily 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 confirmatory of the view you maintain. Along the coast S. and W. of Torquay 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

plateaux round the base of Ingleborough here and there show, in addition to the effect of weathering along joints, a greater gash, due to a fault. Indeed in the cases you are describing there seems to be a close connection between the faults and master-joints. Salter has, I think, called attention to this. At Hunstanton one may see good examples of the characters you describe along the margin of the faults, complicated by the very frequent hardening of the rock by setting of the iron oxides along bands, as described by Judd in the case of the Northamptonshire ironstone."

The longest and usually the most important faults are those belonging to the north-east series. They cut off, and have apparently dislocated some of the faults belonging to the N.W. system, as may be seen in the N.E. part of fig. 2: they are themselves cut off, in other cases, by N.W. faults; thus the N.E. faults seen in fig. 2 terminate against the large, curved N.W. fault at the S.W end of the map. The blocks bounded by the N.E. faults are themselves traversed by faults or fissures running either in a N. W. or N. direction: these faults are limited to the blocks, the boundaries of which they occasionally fail to reach (fig. 2).

It is difficult to state exactly in what order the various faults and dislocations originated, but the circumstance that the continuation of a fault can rarely, if ever, be detected on the two sides of another which cuts it off, suggests that the majority of the faults belong to a single period, the large blocks bounded by the chief faults being broken up into smaller sections, the faults bounding which either terminated against the larger faults, or failed to reach them.

The down-throw of the N.W. faults was very commonly, but not quite universally, on the N.E. side (fig. 1); that of the northerly faults (fig. 2) to the W., whilst in the case of the N.E. faults the throw was usually to the S.E. fig. 2). The N.E. faults, as far as could be observed, were ordinary ones; and the hade of the last-mentioned series was high to the S.E.

It will be seen that the facts given lend no support to the view that the marine depression to the N.W. of the Devonshire (and Cornish) coast is directly due to crust movements, the throw of the N.E. faults, which are parallel to the general direction of this coast

from Morte Point to Land's End, being the reverse of that required. by this hypothesis.

The occurrence of series of faults intersecting one another at right angles is a common phenomenon, and has been particularly pointed out by De la Beche* in S. W. England. One series of faults in these cases is usually approximately parallel to the strike, and the other to the dip of the beds. Such is generally the case in Cornwall and South Devon, as may be seen from the maps and description of De la Beche and Asher. The normal strike of the beds in these regions is approximately E. and W., but in the neighbourhood of the granite it becomes modified, and the faults, mineral veins, and elvans show in many places a deflection more or less parallel to the general trend of the granite masses; the fissures, however, preserve their relations to the strike and dip of the beds. We cannot, accordingly, explain the N.E. and N. W. direction of the main faults near Westward Ho, as a deflection of the fault corresponding to the N. and W. faults of other parts of Devonshire and of Cornwall, since the former cross the strike obliquely; moreover, the latter series is represented in the district, as seen above†, though only to a small extent. The cause of this direction does not seem to be perfectly clear, and may have relation to the direction of the high ground and granite bosses, or be due to merely local conditions, such (as Mr. Ussher suggests to me) as the local development of grits in the Culm Measures of the region. In conclusion we may say, firstly, that everything points to the view that the present configuration of the shore in this region is due solely to denudation acting on a tilted and faulted series of rocks of varying hardness; and secondly, that a fjord-like structure may be produced on a small scale by marine denudation acting along a series of faults and fissures.

EXPLANATION OF FIGURES.

Fig. 1. Portion of the sea coast between tide-marks about a mile to the S. W. of Westward Ho, showing the channels which have been excavated along lines of faulting. The faults themselves are

* Report on the Geology of Cornwall, Devon, and West Somerset, 1839. + De la Beche describes a well-marked N-S. fault at Cornborough, which lies one-third of a mile to the E. of the area shown in fig. 1.

not shown in the map, but their effect in displacing the strata is visible. As far as can be judged from the survey-maps the prevalent direction of the channels in the strip of coast immediately to the S.W. is likewise N.W. The same may be said of the portion of the coast between that represented in figs. 1 and 2, as observed in the field.

Fig. 2. Map showing the principal faults which have effected the Culm Measures exposed in the intertidal platform about twothirds of a mile W. of Westward Ho. The further continuation of the map to the N.E. would show a number of other faults running respectively N.E. and N.W.; the survey map, for instance, shows about six N.E. channels, most of which traverse the whole breadth of the rock exposed.

Fig. 3. View at low water from the summit of the cliff of a portion of the shore between those represented in figs. 1 and 2, showing one of the larger N.W. faults, with a northerly one abutting against it. To the right is seen a second smaller N. W. fault. The small sandstone ridge to the left is separated from the shales to the extreme left by a strike fault. (From a photograph by Mr. Percy Groom.)

Fig. 3a. View at low tide from the top of the cliff of a portion of coast immediately to the N.E. of that shown in fig. 3; the same faults are shown together with other small ones, belonging to the N.W. and N.E. systems. (From a photograph by Mr. Percy Groom.)

Fig. 4. View from summit at cliff of part of the coast shown in fig. 2, immediately to the N.E. of the curved N.W. fault towards the S. W. of that map. The tide is partly up, and the small promontory to the N. of the fault is converted into a number of reefs. traversed by two N.E. and one N. fault. The more northwesterly-situated of the two long N.E. faults. shown in the map, is seen filled with water near the upper right-hand corner, whilst portions of the two southern branches of the westernmost of the three N. faults are seen in the fore-ground. The N. W. curved fault itself is marked by the channel crossing the sandstone ridge to the left. (From a photograph by Mr. Percy Groom.)

Fig. 5. View from summit of cliff of part of coast; on the left

is seen the sandstone band indicated in the middle of fig. 2, and terminating seawards in Rock Nose; this band is traversed by three of the N.E. faults. one at the edge of the pebble-beach, a second in the fore-ground, and a third in the distance. The somewhat rocky portion of the fore-ground is a portion of the sandstone band displaced to the N.E. along the middle N.E. fault traversing the "Mermaids' Pool." Just beyond this is the flat area of shales occurring immediately to the N.N.W. of the sandstone band. On the right-hand side is seen the uppermost part of the broad sandsandstone band occupying the N.E. portion of the map (fig. 2). Seawards appear small inlets excavated along two of the N. W. faults. (From a photograph by Mr. Wilfrid Groom.)