were necessarily accompanied by great migrations of flora and fauna-arctic alpine plants coming to occupy the low-grounds of Central Europe, and northern animals ranging down to the shores of the Mediterranean.

V. SECOND INTERGLACIAL EPOCH.-The enormous morainic accumulations and fluvio-glacial gravels of the second. glacial epoch are sufficient evidence of its prolonged duration. Eventually, however, it passed away and the climate by degrees became temperate and even genial. The arctic-alpine flora and northern. fauna retreated from the low-grounds and were replaced by temperate and southern forms. The character of the plants which then occupied North Germany and Central Russia is suggestive of a milder and less extreme climate than is now experienced in those regions and the mammalian fauna of the epoch, which included the hippopotamus and Elephas antiquus, was in keeping with the flora. Britain would appear to have been connected with the Continent at this time, and land-passages probably joined our Continent to North Africa. Again, however, the climate began to deteriorate, accompanied by renewed migrations of flora and fauna, and as the third glacial epoch approached, much low-lying land in Northern and Northwestern Europe was submerged. The long duration of this interglacial phase is shown by the great depths to which the rivers of the epoch succeeded in eroding their valleys.

VI. THIRD GLACIAL EPOCH.-At the climax of this epoch a most extensive ice-sheet again overwhelmed the major portion of the British Isles and a vast area of the Continent. It did not, however, attain the dimensions of its predecessor. From the Alps great glaciers again descended to the low-grounds, where they dropped the terminal moraines of the "inner zone." These moraines form most conspicuous objects, and extend in curving lines between the highly denuded moraines of the first and second glacial epochs. Like these they are accompanied by well-marked sheets and terraces of fluvio-glacial gravels. Many of the other mountains of Europe were similarly snow-clad and glaciated, while rubble-drifts accumulated in extraglacial regions.

VII. THIRD INTERGLACIAL EPOCH.-The third glacial epoch eventually passed away like its predecessors and was gradually succeeded by temperate conditions. Of this change the most direct evidence we have is that furnished by the youngest interglacial beds of the Baltic coast-lands. It is probable, however, that a considerable proportion of the old alluvial deposits of Britain and Ireland, which have hitherto been classed as of postglacial age, really belong to this interglacial epoch. Amongst these are the clays, etc., with Irish deer, red-deer, etc., which underlie the older peat-bogs. In the Baltic area the interglacial beds contain in some places arctic forms, in others a temperate marine fauna, in yet others they have yielded mammoth, woolly rhinoceros, horse, Irish deer, and urus. It is obvious that these beds cannot be strictly contemporaneous. Some probably belong to

the beginning, others to the middle of the third interglacial epoch, while others again may pertain to its close. They show us clearly, however, that after the disappearance of glacial conditions the Baltic became tenanted by a temperate North Sea fauna, while the adjacent lands supported a corresponding terrestrial fauna and flora.

VIII. FOURTH GLACIAL EPOCH.-In the early stages of this epoch the low-grounds of Scotland were submerged to the extent of 100 ft. at least, while an arctic marine fauna lived round the coasts. Eventually the various mountain-districts of our islands were cased in snow and ice, large glaciers filling all the Highland fiords and calving their icebergs in the sea-a condition of things implying a snow-line not exceeding 1,000 to 1,600 ft. in elevation. But the greatest development of ice was witnessed in the Baltic area. The Scandinavian peninsula once more supported an icesheet that broke away in icebergs at the mouths of all the fiords of Western Norway. Finland was well-nigh overwhelmed, while the Baltic basin was occupied by a great ice-stream which invaded North Germany and Denmark. Later on, as the ice-sheet melted away, a wide area in Scandinavia was submerged in a cold sea which communicated widely with the Baltic. In the Alps large glaciers flowed for long distances down the great valleys, but came far short of attaining the dimensions reached by those of the preceding glacial epoch. At the same time small local glaciers appeared in the high valleys of some of the mountainranges of Middle Europe.

IX. FOURTH INTERGLACIAL EPOCH.-At the climax of this epoch temperate conditions prevailed, and extensive forests of deciduous trees spread far north into regions where such trees no longer flourish. The British Isles now formed part of the Continent. The cold sea had retreated from Scandinavia, and the Baltic was converted into a great lake. Eventually, however, submergence again ensued, but the sea, which now invaded Scandinavia and communicated with the Baltic, was tenanted by a fauna indicative of more genial conditions than obtain at pres

ent.

X. FIFTH GLACIAL EPOCH.-This epoch is characteristically represented by local or valley moraines in the British Isles, the position of which indicates that the snow-line reached in Scotland an average height of 2,500 ft. The disappearance of the genial conditions of the preceding temperate epoch was marked by the submergence of the Scottish coast-lands to a depth of about fifty feet below their present level. Here and there in the northwest of Scotland, glaciers reached the sea and dropped their moraines on the beaches of the period. To the same epoch may be assigned the formation of most of the corrie rock-basins of the British Isles -each of these basins marking the site of a glacier of more or less limited size. The submergence in Scotland probably commenced in the preceding temperate epoch, as it did likewise in AM. JOUR. SCI.-THIRD SERIES, VOL. XLIX, No. 289.—JAN., 1895.

Scandinavia. In the Alps the fifth glacial epoch is marked by the moraines of the so-called "second postglacial stage "-moraines that indicate a renewed advance of the glaciers of that region.

XI. FIFTH INTERGLACIAL EPOCH.-This epoch was heralded by the re-emergence of the land and the retreat of our valley-glaciers. Again the British area attained a wider extent than at present, but we cannot tell whether it became united to the Continent. The upper "buried forests" in the peat-bogs of Northwest Europe show that this epoch was characterized by drier conditions and a remarkable recrudescence of forest-growth-conditions recalling those of the preceding interglacial epoch.

XII. SIXTH GLACIAL EPOCH.-To this epoch belong our latest raised-beaches, which indicate a limited submergence not exceeding, in Scotland, twenty to thirty feet. The climate once more became humid and less favorable to forest-growth. Hence forests decayed while peat-bogs extended their area. The snow-line stood at an elevation in Scotland of 3,500 ft.—and thus nourished a few small glaciers in our loftiest mountain-groups.

XIII. THE PRESENT.-Marked in Britain by the retreat of the sea to its present level, and by the return of milder and drier conditions and the final disappearance of permanent snow fields.

It will be observed that in this short résumé I have abstained from the use of the term "post glacial." The word has been applied to deposits of such widely different ages that it has ceased to be of any value for classificatory purposes. From late Pliocene down to the close of the Pleistocene time we have the record of a continuous series of geographical and climatic changes. Early in the cycle the glacial and interglacial phases attained their extreme development. The climax once passed, each successive cold and genial epoch declined in importance. In a word, the climatic and geographical changes became less and less marked as the cycle drew to a close. From the point of view of the present it seems absurd to speak of "fifth" and "sixth" glacial epochs, seeing that these epochs were marked only by the presence in Britain of limited snow-fields and small local glaciers. When either of these epochs is contrasted with the conditions that obtained in early glacial times they would seem to be more properly described as temperate epochs. But they undoubtedly belong to one and the same series of alternating cold and genial conditions, and from this larger point of view cannot be designated otherwise than glacial.

In the following tabular statements the glacial and interglacial succession is given in ascending order, beginning with the lowest beds-the successive stages being indicated in the several tables by the same numbers.

GLACIAL SUCCESSION IN BRITISH ISLES.

GLACIAL SUCCESSION IN NORTHERN EUROPE.

8. Ancylus-beds of Baltic area; older buried forests generally; Littorina-beds of Baltic area in part.

9. Peat overlying older buried forests; calcareous tufas, &c.; Littorina-beds in part; large valley-moraines in Norway. 10. Younger buried forests.

11. Peat overlying younger buried forests; high-level terminal moraines in Norway.

8. Temperate flora and fauna: climate at climax of stage more genial than now; conditions become more humid in later stages.

9. Humid climate: glaciers here and there reach heads of fiords.

10. Temperate flora and fauna; drier conditions.

11. Humid climate; relatively small glaciers.

GLACIAL SUCCESSION IN CENTRAL AND SOUTHERN EUROPE.

1. Lowest ground-moraines; terminal 1. Accumulations of first glacial moraines opposite mouths of great val- epoch.

leys; plateau-gravels (Alpine Lands). Oldest morainic accumulations of Central France (?)

2. Hötting breccia; lignites of Leffe, &c.; so-called Upper Pliocene alluvia of Central France.

3. Ground - moraines; terminal-moraines of outer zone; high-level gravel terraces (Alpine Lands); "Ceppo" of North Italy; Pleistocene conglomerate of Ligurian coast-lands; torrential gravel terraces of South-west Italy; erratics of raised beaches (France); older moraines of Urals, Carpathians, and mountains of Central Europe; of Central France, Pyrenees, Corsica, Appenines, Balkan Peninsula, &c.; lower breccias of Gibraltar; and rubble-drift, in part, of other regions.

4. Lignites of Switzerland, Bavaria, &c.; alluvial deposits; beach accumulations underlying rubble-drift (Northern France); terraces cut in older breccias of Gibraltar.

5. Ground-moraines; terminal moraines of inner zone; low-level gravel terraces (Alpine Lands); valley-moraines in other mountain-regions; rubble-drifts in part.

6. Alluvial deposits, &c. (?)

7. Terminal moraines in large longitudinal valleys of the Alps; small valleymoraines in the higher valleys of other mountain-regions.

8. Alluvial deposits, &c. (?)

9. Terminal moraines in higher valleys of Central Alps.

10. Alluvial deposits, &c.

11. High-level moraines in Western Alps.