JERSEY CONGLOMERATE. 273 rock on which the fort stands, is a thick vein of mica. Most of the principal fissures range north and south, shifting occasionally a little to the east or west of that bearing. They succeed one another with such exceedingly short intervals that the coast line, for a distance of several miles, can only be compared to the edge of a saw. The indentations are not deep, but their number is countless; and many of them terminate quite abruptly. This condition comes to a climax in the picturesque bay called the Grêve au Lançon, and the headland called Grosnez Point. The south-western extremity of the coast of Jersey is almost equally broken, but not so regularly indented; and this is the case also with Plat Rocque, the south-eastern corner. The Corbiére rocks and the coast from the Corbiéres to the east, as far as St. Brelade's, present as great a variety of form and broken outline as can be found on any coast. We have not yet described the newer conglomerate of the north-eastern corner of Jersey. It is a very singular mass, not at all easy of explanation. For the most part, it is composed of rounded pebbles of all sizes, up to several cubic yards, of which the greatest number, though not the largest of the stones, are chlorite, schists, and other rocks of no great hardness. With these, or replacing them altogether, are large patches made up of pebbles of syenite, hornblende, hornstone, quartzite, and other minerals and rocks, with a vast multitude of jaspery rocks, all indiscriminately mixed and firmly cemented together. Occasionally, angular masses of rock, chiefly chlorite, are cemented into a dark green breccia. On the beach where this conglomerate prevails, there are not only a multitude of pebbles, evidently derived from it, but also a singular profusion of common chalkflints, often of large size, and not always more worn than they are on the south coast of England. The condition of the pebbles and the singular result of their rapid accumulation on the coast will be considered in the next chapter, but the view of the T boulders of Saie Harbour, given in the next page, may be referred to as interesting in reference to the above remarks on the conglomerate, admirably shown in the locality alluded to. On the beach at Grouville Bay, south of the extreme point at which the conglomerate is found, there are also chalk-flints in large numbers, but generally smaller and fragmentary. The proportion of such pebbles is, however, still very large. The conglomerate behind and near St. Catherine's Harbour dips about 30° E.N.E.; and this dip is constant for a distance of more than half a mile. The extreme limit of the deposit seems to be from the middle of St. Catherine's Harbour to the eastern side of Bouley Bay, a distance, in a direct line, of rather more than three miles. The precise geological age of this conglomerate being at present undetermined, and the beds dipping considerably and for the most part to an easterly quarter, it is possible that there may be some connection between them and the Alderney sand-stone. There is, indeed, nothing in common between the two, beyond this general relation to a north and south axis of elevation lifting up the islands through an angle of about 30°. That the Alderney sand-stone is on the north and east of that island, and the Jersey conglomerate on the south and east of Jersey, suggests the possibility that the principal east and west axis lies between the two, and agrees with the position of Guernsey and Sark. These obscure connections, traceable between the islands, introduce hypotheses that may help to direct future enquirers. They can hardly be regarded at present as more than suggestive; but if it should appear that the Alderney sand-stone and the newer conglomerate are contemporaneous, the older Jersey conglomerate may, perhaps, belong to the Cherbourg grits. At a point behind St. Catherine's, and again on the descent of the carriage-road to Bouley Bay, there are small deposits of a very fine red sand-stone, with clayey bands. These deposits are nearly horizontal, and are no doubt modern, but there is FREQUENT UPHEAVALS OF LIMITED EXTENT. 275 nothing in them to mark their precise date. They are situated far above the present level of the sea, and must have been deposited before or during the last great elevation. It becomes, then, quite certain, whatever we may decide as to older disturbances and original elevation, that numerous movements of upheaval, of different amounts and in different directions, have affected the Channel Islands at various times. It is also certain that many of these have been such as to affect each island differently, thus proving the limited extent of the elevating action in such cases; for, had it been large, it must have affected uniformly the comparatively small area containing all the islands and the surrounding sea. Many details have been omitted in this sketch of the crystalline and metamorphic and other older rocks of the Channel Islands, but the outline given may, perhaps, be useful and suggestive. Let us pass on now to the modern deposits, the recent changes of level, and the recent destruction of the coast. CHAPTER XI. GEOLOGY AND MINERALOGY OF THE CHANNEL ISLANDS. MODERN DESTRUCTION AND RENOVATION. THE magnificent scenery, so much admired on the coast of all the Channel Islands; the wild desolation that reigns when the receding tide lays bare needle points, or exhibits alternate floors and walls of granite, in places where a few hours ago the water presented a smooth, but treacherous surface; the broken cliffs, detached headlands, natural arches and recesses, and gloomy caverns; the grotesque rocks, some prominently jutting out, some fallen from above and angular, some rounded and smooth; -all these are the results of an action of wind and water that is going on every year, winter and summer, and that is always tending to reproduce, with little essential variety, the very forms and outlines it is constantly destroying. Scenery representing these picturesque appearances, is pictured with great accuracy in many of the illustrations in this volume.* Such * See more especially the following views:-Cliff and Roche Pendante in Alderney, Chapter I. Gouliot Rock in Sark, Chapter II. Various views of Jersey in Chapter III. The Corbière in Guernsey, Chapter X. chapter. The Burons, Chapter XII. The rocks in the The views in the present Chapter XIII. St. Catherine's Bay, Jersey, Chapter XVIII.; and the Coast Scene in Guernsey, Chapter XIX. These have all been selected and drawn with a special view to illustrate the wild coast scenery of the principal islands. SUBTERRANEAN FORCES. 277 representations are not the less valuable because in a few years they must refer to things of the past, for there will still be in the same, or some near place, a similar specimen of rock scenery, produced on similar material by identical causes. To understand the secret history of the picturesque in these islands, it was necessary that the nature and origin of the rocks should be in some measure learnt, and in the last chapter it has been attempted to give a brief outline of these. It remains now to consider the modern changes, the forces now at work, and the result of their combined agency in our own, or very recent times. In all this, however, we must speak in geological language. What is meant by modern and recent, is very old in comparison with human records, and dates back to a time, when, if men existed, they belonged to races long extinct; races, whose only remains hitherto found are fragments of broken flint or harp stone, wherewith savages might perform those few actions that proclaim their human intellect. The modern influences we allude to in this chapter are several; they include subterranean movements, producing slow upheaval or depression of large tracts; the destroying and reproducing action of the waves in breaking up hard rocks, and accumulating the debris at a distant point; the action of rain and changing temperature; and the action of organic life, modifying in various ways the inorganic forces. That there are forces of the kind just mentioned, the reader, not accustomed to geological investigations, must take for granted. Proofs of them exist in abundance; but it would involve explanations not justified in a work of this kind, to present them to the reader. They are readily found and all the results mentioned are every day events in nature. Assuming then that the syenites and porphyries of the Channel Islands, covered, perhaps, at one time, with numerous and thick deposits, have been slowly brought into their present position, |