Charles Maclaren, Esq., on the Erratics of the Alps. 285 



On the Erratic Formation of the Bernese Alps, and other 

 parts of Switzerland. By Charles Maclaren, Esq., 

 F.R.S.E., F.G.S., and Member of the Geological Society 

 of France. Communicated by the Author. With Map 

 and engraved Illustrations. 



The erratic blocks, or " travelled stones," of Switzerland have 

 long afforded matter of speculation to geologists, though they are 

 rarely noticed by the crowd of fashionable tourists who ramble over 

 its mountains every summer. These blocks are extremely nu- 

 merous, and present themselves in singular and unexpected situa- 

 tions ; they are often of vast size, in some instances as large as a 

 house ; and they are occasionally found at the distance of fifty or a 

 hundred miles from the parent rock. The mode of their trans- 

 portation constitutes a problem about which volumes have been 

 written, and which can scarcely yet be said to have received a sa- 

 tisfactory solution. Fifty years ago, the favourite theory was, that 

 they had been forced along by currents of water. More recently, 

 some have conjectured that they were floated on currents of mud ; 

 but at present, geologists may be divided into two categories, those 

 who believe that the boulders were transported on rafts of floating 

 ice, and tbose who hold that they were conveyed by glaciers of vast 

 size, which had at one period covered all the low country. In the 

 following notes, which are partly the result of two short tours in 

 Switzerland, and partly derived from works written on the subject, 

 originality or novelty of view has not been aimed at. My object 

 has been to shew how the phenomena present themselves to a tra- 

 veller pursuing some of the common routes, and to indicate how the 

 facts are explained by the prevalent hypotheses. 



Map I., representing a part of the Bernese Oberland, well known 

 to tourists, is copied from the map of Keller. 



T, the east end of the Lake of Thun. 



B, the Lake of Brienz. 



L, the Lake of Lungern, in Unterwalden. 



Br, the Village of Brienz. 



F F, the Faulhorn group of mountains. 



M n, the Village of Meyringen. 



G d, the Village of Grindelwald. 



R, the Pass of the Grimsel, leading from the Valley of Hash to 

 the sources of the Rhone (o o) in the Valais. 



r r r , the upper part of the River Aar, which, after a course of 

 25 miles in the Valley of Hasli, flows through the Lakes of 

 Brienz and Thun, and thence proceeds northward to the Rhine, 

 of which it is the largest tributary. 



J WN S V, the principal mass of the Bernese Oberland, comprising 

 one of the most extensive groups of snow-clad mountains in the 



VOL. LIII. NO. CVL— OCTOBER 1852. U 



