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difficulty of understanding how the existing flora of the Faroe Islands, which is of Scandinavian origin, could have reached them without a land connection with northern Europe in Post-glacial times. Mr. A. R. Wallace, however, has shown that the distribution of plants can be effected by other means than those necessary for the distribution of terrestrial animals, and that it is very unsafe to draw inferences from island floras similar to those which may be drawn from their mammalian faunas. His remarks on the flora of the Azores are very convincing, and he concludes with saying that, we have in such facts as these a complete disproof of the necessity for those great changes of sea and land which are continually appealed to by those who think land connection the only efficient means of accounting for the migration of animals and plants."

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The Scandinavian character of the Faroe flora can be explained by other means than the great elevation which would have been required to unite it to Scotland, and we may therefore dismiss Professor Geikie's view of the geography of this period as quite unwarranted by the facts which are known to us. Professor Dawkins stands on safer ground when he assumes that the coast-line during the occupation of Britain by Neolithic man coincided roughly with the 10-fathom contour, but, as already stated, there is good reason for believing that some of the Cornish forests date from a time when the sea did not reach beyond the line of 15 fathoms, and whether the Neolithic invasion took place under these geographical conditions, or at an earlier epoch, it is certain that there was a time when the position of the English and French coasts was approximately that indicated by the inner line on the map, Plate XV.

It is equally clear that in the south of England subsidence

"Island Life," 1880, p. 479.

continued, and that the sea encroached farther and farther on the forest-clad land, the submerged levels being covered with a greater or less thickness of marine clays and sands, while the valleys were converted into estuaries and filled with thick accumulations of alluvial mud. These are the conditions which now exist on our southern and southeastern shores; everything points to a recent submergence, with pauses during which peat beds were formed, and there is no evidence of any more recent upheaval.1 Similar phenomena occur as far north as Lancashire and the south of Yorkshire, but are not found much farther north. I am informed by Mr. Hugh Miller that on the east coast north of Durham there is no proof that the valleys have ever been cut to a lower level, since the Glacial period, than their present depth; and when we reach the Forths of the Forth and Clyde the phenomena connected with valley erosion are altogether different. There are buried forests, and they are covered by marine alluvial clays, but the forests seldom run below low-water mark, and the marine clays are now raised high above it, forming wide plains or "carse-lands" from 30 to 45 feet above mean sea-level.

In Scotland, therefore, it is clear that the last movement was one of upheaval, and it would appear that this upheaval was contemporaneous with or later than what we may call the Neolithic subsidence of England, for the Carseclays contain relics of Neolithic man. If the last movement which our islands have experienced had been similar throughout their extent, England would have had her carse-lands, and the lower tiers of raised beaches which

1 The raised beaches of Brighton, Selsea, Portland, and the Cornish coasts are generally regarded as much older than the submerged forests. They probably date from the previous elevation (Palæolithic time), and must not be confounded with the 25 and 50-feet terraces of the Scottish coast.

occur on the Scottish shores would have been traceable along the rocky coasts of Wales and Ireland. As a matter of fact, the lowest or 25-feet beach descends to lower and lower levels along the east coast of Ireland, and coincides with the present level of the sea in the neighbourhood of Dublin.

We may therefore conclude that though the buried. forests of Scotland grew, like those of England, during a period of subsidence, either this subsidence did not last so long in the former country as it did in England, but was succeeded by a reverse movement while the south of England was still sinking, or else that after the subsidence had affected both countries to the same extent, an upheaval took place in Scotland while the greater part of England and Ireland remained in a stationary condition. It is only on one of these two suppositions that the phenomena of raised beaches and buried forests in England, Scotland, and Ireland can be satisfactorily accounted for.

CHAPTER XIV.

SUMMARY OF THE GEOGRAPHICAL EVOLUTION OF THE

IN

BRITISH ISLES.

N this concluding chapter it is my intention to review the series of geographical mutations which have been described in the preceding pages, to take note of the relative age of the diverse physical districts which make up the British Islands, and to consider how far the geographical restorations which have been attempted can be regarded as consecutive stages in the building and fashioning of that part of north-western Europe which may be called the British region, meaning by this term not only the actual land-tracts which constitute Great Britain, Ireland, and the adjacent islands, but also the narrow seas which separate them from one another and from the continent of Europe.

Geologists can hardly now subscribe to the Huttonian dictum that no traces are to be found of a beginning in the world's economy, but the glimpses which we have obtained into the physical conditions of the earliest Cambrian epoch do not warrant us in attempting any definite delineation of land and sea. Nor is our knowledge of the succeeding Palæozoic periods sufficiently complete to make our reconstructions more than guesses at the truth. Indeed, the geologist who is attempting to restore the geography of any epoch of Paleozoic time may be compared to an archæologist who is examining the ruins of a temple

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