146 xiLPINE ERRATICS. [Ck. XII 



mountains of Scandinavia, Scotland, and Switzerland, may have been 

 less elevated tlian at present. But if in both of the polar regions a 

 considerable area of elevated dry land existed, such a concurrence of re- 

 frigerating conditions in both hemispheres might have created for a time 

 an intensity of cold never experienced since ; and such probably was the 

 state of things during that period of submergence to which I have 

 alluded in this chapter. 



Alj^ine erratics. — Although the arctic regions constitute the great 

 centre from which erratics have travelled southwards in all directions in 

 Europe and North America, yet there are some mountains, as I have 

 already stated, like those of North Wales and the Alps, which have 

 served as separate and independent centres for the dispersion of blocks. 

 In illustration of this fact, the Alps deserve particular attention, not only 

 from their magnitude, but because they lie beyond the ordinary limits ot 

 the "northern drift" of Europe, being situated between the 44th and 

 47th degrees of north latitude. On the flanks of these mountains, and 

 on the Subalpine ranges of hills or plains adjoining them, those appear- 

 ances which have been so often alluded to, as distinguishing or accom- 

 panying the drift, between the 50th and YOth parallels of north latitude, 

 suddenly reappear, to assume in a more southern country their most 

 exaggerated form. "Where the Alps are highest, the largest erratic blocks 

 have been sent forth, as, for example, from the regions of Mont Blanc 

 and Monte Rosa, into the adjoining parts of France, Switzerland, Austria, 

 and Italy, while in districts where the great chain sinks in altitude, as 

 in Carinthia, Carniola, and elsewhere, no such rocky fragments, or a 

 few only, and of smaller bulk, have been detached and transported to a 

 distance. 



In the year 1821, M. Venetz first announced his opinion that the 

 Alpine glaciers must formerly have extended far beyond their present 

 limits, and the proofs appealed to by him in confirmation of this doctrine 

 were afterwards acknowledged by M. Charpentier, who strengthened 

 them by new observations and arguments, and declared, in 1836, his 

 conviction that the glaciers of the Alps must once have reached as far 

 as the Jura, and have carried thither their moraines across the great 

 valley of Switzerland. M. Agassiz, after several excursions in the Alps 

 with M. Charpentier, and after devoting himself some years to the study 

 of glaciers, published, in 1840, an admirable description of them, and 

 of the marks which attest the former action of gTeat masses of ice over 

 the entire surface of the Alps and the surrounding country.^ He pointed 

 out that the surface of every large glacier is strewed over with gravel 

 and stones detached from the surrounding precipices by frost, rain, light- 

 ning, or avalanches. And he described more carefully than preceding 

 ■writers the long lines of these stones, which settle on the sides of tho 

 glacier, and are called the lateral moraines ; those found at the lower 

 end of the ice being called terminal moraines. Such heaps of earth and 



* Agassiz, Etudes sur les Glaciers, and Systerae Glaciure. 



