312 Charles Maclaren, Esq., on the 



surfaces of hollow recesses, into which a large iceberg or floe could 

 not enter ? The glacier, on the other hand, striates rocks under 

 these various circumstances before our eyes. A more radical dif- 

 ficulty yet applies to the iceberg theory. Whence did the water 

 come on which the ice floated ? Shall we say, from the sea ? This 

 would amount to the very bold assumption that the Alps had been 

 submerged to the depth of 6000 or 7000 feet for many thousand 

 years, and then raised up again, within the post-tertiary period ! 

 Passing over other objections, the assumption is refuted by the fact, 

 that the Erratic Formation, or " Terrain Morainique" of the Swiss 

 plain, rests, not upon marine beds, such as the sea in its supposed 

 long sojourn should have left there, but upon a stratified deposit 

 called the " Alpine Diluvium,'' which in its upper part contains the 

 bones of the existing Swiss Mammalia, and at the bottom those of 

 Eiephas primigenius associated with fresh-water shells. Pictet, the 

 learned palaeontologist of Geneva, holds that the formation of this 

 Diluvium belongs to the modern or current period, that its fauna 

 was essentially the same with the present one, no new species hav- 

 ing been added, but merely a few having died out. He thinks, 

 however, that the Diluvium of Switzerland is more recent than the 

 deposits bearing that name in Europe generally. (Pictet, Memoire 

 sur des ossements trouves dans les graviers stratifies des environs de 

 Mategnin. Geneve, 1845 ; C. Martins et B. Castaldi, sur les Ter- 

 rains Superficiels de la Vallee du Po compares a ceux du Bassin 

 Helvetique, 1850). Perhaps it may be said that the icebergs floated 

 on a natural lake. But if so, we ask, with Forbes, what were its 

 boundaries, and where were the barriers which maintained a vast 

 sheet of water at a level of 2000 feet above the surface of the coun- 

 try ? " Such barriers cannot be pointed out, consistently with what 

 is known as to the unchanged condition of the superficial deposit in 

 Switzerland generally, since the period of the transport of erratics." 

 On a survey, then, of all the facts known respecting the distribution 

 of the Swiss boulders and the constitution and agency of glaciers, 

 the evidence seems decidedly to preponderate in favour of Charpen- 

 tier's doctrine, that the Alpine blocks found on Jura and in the 

 plain were transported by glaciers. There are no doubt some dif- 

 ficulties attending this conclusion, but these may be removed by 

 future research. 



Ancient Glaciers 1 Rate of Motion. 

 Several questions present themselves respecting the glacial period 

 in the Alps, to which satisfactory answers cannot be given. We 

 cannot tell what caused it, or how long it endured, or what length of 

 time has elapsed since it ceased — that is, since the glaciers retreated 

 from the plain to those higher valleys in the mountains which they 

 now occupy. Agassiz thinks that a fall of mean temperature equal 

 to 8 degrees centigrade, or 14£ of Fahrenheit, would give the glaciers 



