302 Charles Maekren, Liaq., on the 



as a goodiy house of three storeys ! Now, M. Charpentier ascer- 

 tained from its composition, that the boulder is a portion of a rock on 

 the south-east part of the valley (near t). From this point it had 

 travelled round by the valley, e, (for there is no other outlet), per- 

 forming a journey of 150 miles, to A, where it now lies, a monument 

 of the vast powers which nature has at her command, and of tlfe 

 mighty physical changes which this part of Europe has undergone. 



We have further evidence of glacier agency in the fact that the 

 blocks and debris on the two sides of the Rhone are kept wonderfully 

 distinct. The valley of Entremont, for example, at p, and the val- 

 leys of St Nicolas and Saas between b and n. bring down from the 

 Pennine chain or southern ridge (if t), thousands of fragments great 

 and small, of the rocks pecular to each, talcose granite, chloritic 

 gneiss, diallage, and serpentine. These abound along the left side 

 of the valley, and are diffused far and wide over the Swiss plain ; 

 but what on a first view seems strange, none of them have been car- 

 ried across the valley to c or q. Those from 6, for instance, are i 

 found high on the slopes of Jura at /, a hundred miles from their 

 parent rock, while they are not found on the ridge (y v) just opposite. 

 Now, a similar law of distribution is peculiar to a glacier. The de- 

 bris which collects on its right and left flanks, forming its lateral 

 moraines, may be carried many miles downwards ; and yet (unless 

 they are forced together at a narrow gorge) not a block will pass 

 from the one side to the other, though the space which divides them 

 may be small. Had the blocks been transported on masses of float- 

 ing ice, and acted upon, of course, by winds and currents, this re- 

 markable separation could not have been maintained. 



While the larger portion of the fragments derived from the Great 

 Valley went eastward, and were diffused over the space kfh i, another 

 portion, and at a later period, as M. Guyot thinks, went in the op- 

 posite direction, and formed the western glacier, whose course was 

 through the Lake of Geneva (G), to the western part of Jura. Its 

 right moraine was midway between /and g; its left ran along the 

 south shore of the lake, and its frontal or terminal moraine was at S. 

 To me, however, it appears that the whole ridge of Jura from S to h 

 should be considered as part of the terminal moraine. 



The blocks on the middle region of Jura, from / westward, and 

 above the Lake of Neuchatel (N), from two zones. The upper 

 reaches an elevation of 2000 feet ; the elevation of the lower is from 

 500 to 1000 feet; and between them is a zone 1000 feet broad, 

 nearly destitute of blocks. The granites of Mont Blanc from u, and 

 the various rocks of the Pennine chain from t to p, constitute the 

 higher zone almost exclusively. They are found in the lower zone 

 also, but mixed with others. Though Jura is the extreme boundary 

 of the erratic basin, the blocks are much more numerous on it than 

 in the plain — a fact quite in harmony with the glacier hypothesis, 

 for the plain would only receive the blocks which happened to be 



