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of land and water, and that “we are face to face with a problem whose solution must be attempted and doubtless completed by the astronomer.”*

There is another branch of the subject that I cannot so easily leave. It is the answer to the question, What became of the many peculiar tropical American genera of animals and plants, when a great part of the tropics was covered with ice, and the climate of the lower lands much colder than now ? For instance, the Heliconii and Morphos are a group of butterflies peculiar to tropical America, containing many distinct genera which, on any theory of descent from a common progenitor, must have originated ages before the glacial period. How is it that such peculiarly tropical groups were not exterminated by the cold of the glacial period, or if able to stand the cold, that they did not spread into temperate regions on the retreat of the ice? I believe the answer is, that there was much extermination during the glacial period, that many species and some genera, as, for instance, the American horse, did not survive it, and that some of the great gaps that now exist in natural history were then made; but that a refuge was found for many species, on lands now below the ocean, that were uncovered by the lowering of the sea caused by the immense quantity of water that was locked up in frozen masses on the land.

Mr. Alfred Tylor considers that the ice cap of the glacial period was the cause of a great reduction of the level of the sea, amounting to at least 600 feet. But

* I have since discussed this question in the Quarterly Journal of Science for October 1874.

+ Geological Magazine, vol. ix. p. 392.

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if we admit that the ice existed in both hemispheres at the same time, we shall have to speculate on a lowering of the level of the sea to at least 1000 feet. We have many facts tending to prove that during the extreme extent of the glacial period the land stood much higher relatively to the sea than it now does. Professor Hartt believes that during the time of the drift, Brazil stood at a much higher level than at present,* and we can, on the supposition of a general lowering of the sea all over the world, account for the distribution of animal life over islands now separated by shallow seas. Thus Mr. Bland, in a paper read before the American Philosophical Society, on “The Geology and Physical Geography of the West Indies, with reference to the distribution of Mollusca,” states his opinion that Porto Rico, the Virgins, the Anguilla group, Cuba, the Bahamas, and Hayti, once formed continuous dry land that obtained its land molluscs from Central America, and Mexico. The land molluscs of the islands to the south, on the contrary, from Barbuda and St. Kitt's down to Trinidad, are of two types, one Venezuelan, the other Guianian; the western side of the supposed continuous land, namely, Trinidad, Tobago, Grenada, the Grenadines, St. Vincent, and St. Lucia, belonging to the first type; the eastern side, from Barbados to Antigua, to the second.t

Commenting on Mr. Bland's valuable communication, Mr. Kingsley justly says: “If this be so, a glance at the map will show the vast destruction of tropic land during

* “Geology and Physical Geography of Brazil,” by Ch. Fred. Hartt, p. 573.

+ Quoted in “ At Last,” by Charles Kingsley, p. 305.

almost the very latest geological epoch; and show, too, how little, in the present imperfect state of our knowledge, we ought to dare any speculations as to the absence of man, as well as of other creatures, on those great lands destroyed. For, to supply the dry land which Mr. Bland's theory needs, we shall have to conceive a junction, reaching over at least five degrees of latitude, between the north of British Guiana and Barbados; and may freely indulge in the dream that the waters of the Orinoco, when they ran over the lowlands of Trinidad, passed east of Tobago, then northward between Barbados and St. Lucia, afterwards turning westward between the latter island and Martinique, and that the mighty estuary—for a great part at least of that line-formed the original barrier which kept the land shells of Venezuela apart from those of Guiana.”*

A very similar theory has been propounded by Mr. Wallace to account for the distribution of the faunas of the Malay Archipelago, in his admirable work on the natural history of that region.f Java, Sumatra, and Borneo are separated from each other, and from the continent of Asia, by a shallow sea less than six hundred feet in depth, and must at one time have been connected by continuous land to allow of the elephant and tapir of Sumatra and Borneo, the rhinoceros of Sumatra and Java, and the wild cattle of Borneo and Java, to spread from the continent to these now sea-surrounded lands, as none of these large animals could have passed over the arms of the sea that now separate them. The smaller mammals, the birds, and insects, all illustrate this view,

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almost all the genera found in any of the islands occurring also on the Asiatic continent, and the species being often identical. On the other hand, the fauna of islands to the eastward are more closely connected with Australia, and must at one time have been joined to it by nearly continuous land. Honeysuckers and lories take the place of the woodpeckers, barbets, trogons, and fruit thrushes of the western islands, and the many mammals belonging to Asiatic genera are no more seen.

Mr. Wallace ascribes the present isolation of the islands, and their separation from the adjoining continents, to the submergence of the channels between them caused by the abstraction of matter thrown out by the numerous volcanoes. Looking, however, at the fact that at the time when these islands were probably connected with the continents of Asia on the one side and Australasia on the other, namely, at the close of the pliocene period, England was connected with the continent; Malta, as shown by its fossil elephants, with Africa; the West Indies with Yucatan and Venezuela; it seems to me more probable that the cause was not a local one, but a general lowering of the waters of the ocean all over the world to at least one thousand feet,-produced by the prodigious quantity of water locked up in the frozen masses that covered a great part of both hemispheres.

The wide diffusion of the Malayan dialects over the Pacific, reaching as far as the Sandwich Islands, shows the great extension of that race in former times. On numerous islands in Polynesia there are cyclopean ruins utterly out of keeping with their present size and population. Who can look at the pictures of little Easter Island, with its gigantic images standing up in unworshipped solitude, without feeling that that insignificant islet could never have supported the race that reared the monuments. But if that and other islands were once hills overlooking peopled lowlands, the sense of incongruity vanishes. We see the images, not gazing gloomily over the ocean that narrowly circles them in, but proudly looking across wide plains peopled by their worshippers, who from their villages and fields behold the gods they adore, and implore their protection and support.

Was the fabled Atlantis really a myth, or was it that great continent in the Atlantic laid bare by the lowering of the ocean, on which the present West Indian islands were mountains, rising high above the level and fertile plains that are now covered by the sea ? Obscurely the accounts of it have come down to us from the dim past, but there is a remarkable coincidence between the traditions that have been handed down on the two sides of the Atlantic.

In a fragment of the works of Theopompus, who lived in the fourth century before the Christian era, is an account of a conversation between Silenus and Midas, the king of Phrygia, in which the former tells the king that Europe, Asia, and Africa were surrounded by the sea, but that beyond them was an island of immense size, in which were many great cities, and nations with laws and customs very different from theirs. Plato, in his “ Timæus and Critias,” relates that Solon was told by a priest of Sais, from the sacred inscriptions in the temple, how Solon's country “once opposed a power

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