Very recently botany has come to the assistance of geology, in a manner as remarkable as it was unsuspected. It appears that, along the coast line of Great Britain and Ireland, there are several distinct floras or groups of plants, and all geographically related to existing families on the opposite coasts of the Continent. The flora of the west of Ireland corresponds to that on the north-west of Spain—the south-west of England, and also of Ireland, presents groups allied to those on the north-west of France,—and, again, one is common to the north coast line of France, and south-east of England,—while the fourth and fifth have their types in the alpine flora developed in the Scottish and Welsh mountains, and the mixed and diversified tribes more generally distributed over Ireland, England, and Germany. The assumption implied in this botanic speculation is, that these are the remains of a state of things no longer enduring, proofs of the existence of hotter or colder climates than now prevail, and the indications of a configuration of land and sea when a great mountain barrier extended across the Atlantic from Ireland to Spain. The distribution of the second and third sets of vegetation depended on the connection of England with France and Germany, when a sea covered a large portion of the south of Europe, and the upheaval of whose bed, which constitutes the latest of the tertiary deposits, gave rise to a vast continent, comprising Spain, Ireland, the north of Africa, the Azores, and the Canaries. The alpine flora of Scotland and Wales was effected during the glacial period—to be afterward noticed—when the mountain summits of Britain were low islands or members of an archipelago extending over the Frozen Ocean, and clothed with an arctic vegetation which, in the gradual upheaval of those islands and consequent change of climate, became limited to the summits of the still existing mountains. Professor Edward Forbes, adopting in this curious speculation the views of Mr. Hewet Watson, finds a corroboration of them in the peculiar distribution of _endemic_ animals, especially of the marine and terrestrial mollusca. And he justly concludes that all the changes required for the events which he would connect with the distribution of the British flora, are borne out by the geological phenomena that prevailed during the epoch of the several tertiary deposits.