GLACIAL SUCCESSION IN EUROPE. 137 



when there was 12 or 14 inches in circumference of solid bone almost as hard and sound 

 as ivory, it was snapped across." It is remarkable that in this one small bog nearly one 

 hundred heads of Megaceros have been dug up. 



Mr Williams' observations show us that the Megaceros-beds are certainly older than 

 the peat-bogs with their buried timber. When he first informed me of the result of his 

 researches (1880), I did not believe the Megaceros-beds could be older than the latest 

 cold phase of the Ice Age. I thought that they were later in date than our last general 

 mer de glace, and I think so still, for they obviously rest upon its ground-moraine. But 

 since I now recognise that our upper boulder-clay is not the product of the last glacial 

 epoch, it seems to me highly probable that the Megaceros-beds are of interglacial age — » 

 that, in short, they occupy the horizon of the interglacial deposits of North Germany, &c.; 

 The appearances described by Mr Williams in connection with the "grey clay" seem 

 strongly suggestive of ice-action. Ballybetagh Bog occurs at an elevation of 800 feet 

 above the sea, in the neighbourhood of the Three Rock Mountains (1479 feet), and during 

 the epoch of great valley-glaciers the climatic conditions of that region must have been 

 severe. But, without having visited the locality in question, I should hesitate to say 

 that the phenomena necessarily point to local glaciation. Probably frost, lake-ice, and 

 thick accumulations of snow and neve might suffice to account for the various facts cited 

 by Mr Williams. 



I have called special attention to these Irish lacustrine beds, because it is highly 

 probable that the postglacial age of similar alluvia occurring in many other places in 

 these islands has hitherto been assumed and not proved. Now that we know, however,; 

 that a long interglacial stage succeeded the disappearance of the last general mer de 

 glace, we may feel sure that the older alluvia of our lowland districts cannot belong 

 exclusively to postglacial times. The local ice-sheets and great glaciers of our "third" 

 glacial epoch were confined to our mountain regions ; and in the Lowlands, therefore, 

 which were not invaded, we ought to have the lacustrine and fluviatile accumulations b£ 

 the preceding interglacial stage. A fresh interest noW. attaches to our older alluvia, 

 which must be carefully re-examined in the new light thus thrown upon them. 



Turning next to the Alpine Lands of Central Europe, we find that geologists there 

 have for many years recognised two glacial epochs. Hence, like their confreres in 

 Northern Europe, they speak of "first" and "second" glacial epochs.* Within recent 

 years, however, Professor Penck has shown that the Alps have experienced at least three 

 separate periods of glaciation. He describes three distinct ground-moraines, with 

 associated river-terraces and interglacial deposits in the valleys of the Bavarian Alps, 

 and his observations have been confirmed by Professor Bruckner and Dr Bohm. t The 



* Morlot, Bulletin de la Soc. Vaud. d. Sciences nat., 1854, 1858, 1860 ; Deicke, Bericht. d. St. Gall, naturf. ges., 

 1858 ; Heer, Urwelt der Schweiz; Mohlberg, Festschrift d. aarg. naturf. Ges. z. Feier ihrer 500 Site., 1869 ; Rothpletz, 

 Denkschr. d. schweizer. Ges. f. d. ges. Naturwissensch., Bd. xxviii., 1881 ; Wettstein, Geologie v. Zurich u. Umgebung, 

 1885 ; Baltzer, Mitteil. d. naturf. Ges Bern, 1887 ; Renevier, Bull, de la Soc. helvet. d. Sciences nat., 1887. 



t Penck, Die Vergletscherung d. deutschen .Alpen, 1882 ; Bruckner, " Die Vergletscherung des Salzachgebietes," 

 Geogr. Abliandl. Witn, Bd. i. ; Bohm, Jahrb. der Jc. h. geol. Beichsanst, 1884, 1885 ; see also O. Fraas, Neues Jahrb. f. 

 Min. Geol. u. Palceont., 1880, Bd. i. p. 218; E. Fugger and C. Kastner, Verhandl. d. k. Jc. geol. Beichsanst, 1883, p. 136. 



