GLACIAL SUCCESSION IN EUKOPE. 139 



first of these epochs a large glacier flowed from Mont Dore. After its retreat a prolonged 

 interglacial epoch followed, during which the old morainic deposits and the rocks they 

 rest upon were much eroded. In the valleys and hollows thus excavated freshwater 

 beds occur which have yielded relics of an abundant flora, together with the remains of 

 Elephas rneridionalis, Rhinoceros leptorhinus, &c. After the deposition of these fresh- 

 water alluvia, glaciers again descended the valleys and covered the interglacial beds with 

 their moraines. Similar results have been obtained by M. Rames from a study of the 

 glacial phenomenon of Cantal, which he shows belong to two separate epochs. 4 ' 5 ' The 

 interval between the formation of the two series of glacial accumulations must have been 

 prolonged, for the valleys during that interval were in some places eroded to a depth of 

 900 feet. M. Rames further recognises that the second glacial epoch was distinguished 

 by two advances of valley-glaciers, separated by a marked episode of fusion. Dr Julien 

 has likewise noted the evidence for two episodes of fusion during the first extension of 

 the glaciers of the Puy de Dome. 



Two glacial epochs have similarly been admitted for the Pyrenees ; t but Dr Penck 

 some years ago brought forward evidence to show that these mountains, like the Alps, 

 have experienced three separate and distinct periods of glaciation. J 



We may now return to Scotland, and consider briefly the changes that followed upon 

 the disappearance of the local ice-sheets and large valley -glaciers of our mountain regions. 

 The evidence is fortunately clear and complete. In the valley of the Tay, for example, 

 at and below Perth, we encounter the following succession of deposits : — 



6. Recent alluvia. 



5. Carse-deposits, 45 feet above sea-level. 



4. Peat and forest bed. 



3. Old alluvia. 



2. Clays, &c, of 100-feet beach. 



1. Boulder-clay. 



The old alluvia (3) are obviously of fluviatile origin, and show us that after the 

 deposition of the clays, &c, of the 100-feet beach the sea retreated, and allowed the Tay 

 and its tributaries to plough their way down through the marine and estuarine deposits 

 of the " third " glacial epoch. These deposits would appear to have extended at first as 

 a broad and approximately level plain over all the lower reaches of the valleys. Through 

 this plain the Tay and the Earn cut their way to a depth of more than 100 feet, and 

 gradually removed all the material over a course which can hardly be less than 2 miles 

 in breadth below the Bridge of Earn, and considerably exceeds that in the Carse of 

 Gowrie. No organic remains occur in the " old alluvia," but the deposits consist princi- 

 pally of gravel and sand, and show not a trace of ice-action. Immediately overlying 



* Bull. Soc. gM. de France, 1884 ; see also M. Boule, Bull, de la Soc. philomath, de Paris, 8 e Ser. i. p. 87. 

 t Garrigou, Bull. Soc. gM. de France, 2 e Ser. xxiv. p. 577 ; Jeanbernat, Bull, de la Soc. d'Hist. nat. de Toulouse, 

 iv. pp. 114, 138 ; Piette, Bull. Soc. gM. de France, 3 e Ser. ii. pp. 503, 507. 

 J Mitteilungen d. Vereinsf. Erdhunde zu Leipzig, 1883. 



