COMPARISON OF INDIVIDUALS.

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Guernsey collections most of the specimens have been reared this way, and it is clear that this fact may so far influence the result, as to destroy the value of the generalisation. On the other hand, the same naturalist states that, by special attention to feeding, insects may be obtained actually larger than those in a state of nature. As some collections are made from larvæ kept in confinement, and some from insects caught in the perfect state, it is clear that without much preliminary caution as this, no weight and no measure, no individual observation and no mass of averages, would be of any scientific value.

Bearing in mind these possibilities, we may proceed to allude to a few facts that seem to have a bearing on the question at issue.

In the following short list, the first table contains such butterflies as, allowing for the exceptions already suggested, appear, on a careful inspection, combined with a comparison, of more collections than one, to be larger, as individuals, than their equivalents in England; the second, those which, similarly viewed, seemed smaller.

To which add (from Moths) urapterix sambucaria, which a pre-eminently trustworthy collector has never found equal to the English measurements.

There is just a fragment of a system in this: the large Coliades being French and South-English, rather than truly British, butterflies; the small species of vanessa and grapta being thoroughly English, and (as is instanced by the absence of grapta C. album in Guernsey, though found in Jersey) only in part insular. There is a fragment, then, of a system in the evidence as far as it goes; just enough to guard against generalization and to stimulate to wider and more minute enquiries.

Pieris daplidice, like grapta C. album, although found in Jersey, has yet to be discovered in Guernsey. Considering that it is taken on the coast of Kent, and even in the neighbourhood of Brighton, its absence is remarkable. Unless the south-coast specimens crossed the Straits of Dover, or unless there were certain inordinately favourable winds, their presence in Sussex and their absence in Guernsey is strange.

The polyommatus bæticus—a variety in each locality—has also been found at Brighton as well as in Guernsey. On the 5th of August, 1860, Mr. Newman, junior, forwarded it to Mr. Doubleday, who determined the species; and Mr. Newman, senior, thus notices it:-"The species is common on the Continent, and was seen in profusion along the northern coast of France, and in the Channel Islands."

Speaking generally, the characteristic species of the islands are not precisely those of France, and by no means those of England. Still, the West of England, as it approaches Guernsey in climate, does not depart widely either in its Fauna or Flora. As has been intimated in the valuable remarks by Dr. Bowerbank, quoted in the account of the sponges, there is a kind of overlapping zone in the outlying islands of Guernsey and Sark; so that these localities include much that is peculiar both in north-western Europe and south-western England and Ireland.

The result of generalisations concerning these and other species that exhibit differences, whether between the different islands or between the islands and France, may be stated in a very few words. They bear upon the important inquiry, as to whether the islands are portions of an old continent, gradually diminishing, or of a new continent, gradually increasing.

This question may be considered as settled very positively by the lists presented in the chapters on Botany and Zoology. There is too much resemblance to the natural history of Western Europe, and too large a number of species, to justify any

NO GREAT MODERN SUBSIDENCE.

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one in suggesting the bare possibility that they belong to a rising mass of land, receiving its species by migration across water. The number of species is so very large in all departments, and in all the islands, that the separation from the main land is not only certain, but must have been an event recent in the ordinary geological sense of that expression.

The very remarkable state of the land and sea bottom in the open gulf or bay in which are the rocks and islands we have been describing, coupled with some apparent historical evidence, the value of which will be considered in another chapter, has, however, induced a suspicion among many persons, both English and French, that an important depression of European land in the neighbourhood of the Channel Islands, took place so recently as about the end of the eighth century; and again, others less considerable, at many subsequent times, amounting in all to as much as 150 feet.*

At present, then, it must be sufficient to state in general language, that the zoology and botany of the island, as far as they are known, do not support such a view. The islands have no doubt been detached from France, recently enough in one sense, but not in the historic sense. Nor does it seem probable, that since the introduction of the prevailing species any of the islands have existed at a very different level, whether higher or lower, from that they now have.

While on the one hand there is no biological or historical evidence of this great depression, or of the recent separation of the islands from the main land, or from each other, so, on the other hand, is there no geological evidence of recent subsidence.

This view is adopted by M. de Quatrefages in the book already referred to, and is evidently favoured by other writers, although no tangible arguments are brought forward. A gentleman residing in Jersey is about to publish evidence to the same purport, which he considers sufficient to justify the conclusion which is here controverted, and which will be noticed somewhat more fully in a subsequent chapter on the archæology of the islands.

X

But there is evidence, and that of the strongest kind, everywhere exhibited, of the extremely rapid and powerful destroying action of the sea, which here exercises its influence under peculiarly favourable circumstances.

Nowhere on our shores is the tidal wave so powerful, nowhere are the storm waves so frequent; nowhere is there a coast consisting of material in which so much rock of extreme hardness is penetrated so thoroughly with veins of softer material. The very hardness of the granite, where it is hard, produces an unusual destruction of the softer veins; for, as already explained, every fragment removed becomes a hammer, helping to undermine what is left. Whenever one hard mass is thrown down and broken up another is soon attacked, and thus a perpetual and rapid destruction is caused, increasing constantly in area, and not diminishing in intensity.

It must not hence be concluded that there is no evidence of other disturbance than marine action in these islands. No doubt both the raised beaches and depressed peat beds point clearly to local disturbances of elevation, amounting certainly to as much as thirty feet in both directions. That these have been very partial, and that the raised beaches are among the most modern of the two, is however more than probable; while it is certain that neither of them are traceably connected with larger subsidences, such as are assumed by those who explain the separation of the islands from France, and from each other, in this way.

END OF PART THE SECOND.