We need not be surprised that interglacial beds should be well developed underneath the bottom-moraine of that great glacier, while they have not yet been recognised below the corresponding morainic accumulations of our Highlands and Uplands. The conditions in the low-grounds of the Baltic coast-lands favoured their preservation, for the ice in those regions formed a broad _mer de glace_, under the peripheral areas of which sub-glacial erosion was necessarily at a minimum and the accumulation at a maximum. In our Scottish mountain-valleys, however, the very opposite was the case. The conditions obtaining there were not at all comparable to those that characterised the low-grounds of northern Germany, etc., but were quite analogous to those of Norway, where, as in our own mountain-regions, interglacial beds are similarly wanting. It is quite possible, however, that patches of such deposits may yet be met with underneath our younger moraines, and they ought certainly to be looked for. But whether they occur or not in our mountain-valleys, it is certain that some of the older alluvia of our Lowlands must belong to this horizon. Hitherto all alluvial beds that overlie our upper boulder-clay have been classified as post-glacial; but since we have ascertained that our latest _mer de glace_ was succeeded by genial interglacial conditions, we may be sure that records of that temperate epoch will yet be recognised in such Lowland tracts as were never reached by the glaciers of the succeeding cold epoch. Hence, I believe that some of our so-called "post-glacial" alluvia will eventually be assigned to an interglacial horizon. Amongst these may be cited the old peat and freshwater beds that rest upon the upper boulder-clay at Hailes Quarry, near Edinburgh. To the same horizon, in all probability, belong the clays, with Megaceros, etc., which occur so frequently underneath the peat-bogs of Ireland. An interesting account of these was given some years ago by Mr. Williams,[CH] who, as a collector of Megaceros remains, had the best opportunity of ascertaining the nature of the deposits in which these occur. He gives a section of Ballybetagh Bog, nine miles south-east of Dublin, which is as follows:-- 1. Boulder-clay. 2. Fine tenacious clay, without stones. 3. Yellowish clay, largely composed of vegetable matter. 4. Brownish clay, with remains of Megaceros. 5. Greyish clay. 6. Peat. [CH] _Geol. Mag._, 1881, p. 354.