the era of depression beneath the sea. 3. And, lastly, on the land re-emerging from the sea the second ice or glacial period began. The climate during the marine depression must obviously have been milder than that of either of the glacial periods, because of the moderating effect of the wide extent of sea. The exact relation of the boulder clays with marine shells, in the centre and south of Britain, to the detritus left behind by the ice-sheet in the north, has not as yet been satisfactorily ascertained. It is very probable that the elevation of land in the north was simultaneous with a southern depression, which allowed of icebergs depositing their burdens in the eastern counties, in the valley of the Thames, and as far south as Selsea, on the coast of Sussex. _Three Climatal Changes represented on the Continent._ These changes of climate have also been observed on the continent of Europe. The Swiss geologists have shown that the Alpine glaciers extended farther than they do at the present time, and that they present two stages of extension, the first of which is of greater magnitude than the second. The Alpine blocks and moraines have been traced far down into the plains of Lombardy, northwards into the valley of the Rhine, and in France as far south in the valley of the Rhone as Valence. The admirable essay and map brought by MM. Falsan and Chantre, before the meeting of the French Association for the Advancement of Science at Lyons, in 1873, show that there were two periods of glaciation in the valley of the Rhone, the one being due to the movement of an ice-sheet irrespective of the lower hills, the other being merely the work of the glaciers localized in the valleys. These in all probability correspond in point of time with the like stages of the complicated glacial phenomena in Britain. At this time the glaciers of the Pyrenees, now so small, extended at least from thirty to forty miles from their present position down into the plains, leaving behind most astounding evidences of their presence in the valley of the Garonne and elsewhere. On the Spanish frontier, for example, one of the precipitous sides of the valley, near the Pont du Roy, is so smoothed and polished that it is bare of vegetation except in the deep grooves, which offer a precarious support to the roots of ferns and of dwarf beeches. The hills of Dauphiny also and Auvergne were crowned with glaciers, and those of the latter have been shown by MM. Falsan and Chantre to have been conterminous with those of the Alps.