544 



DIFFERENT HEIGHTS AT WHICH BOWLDERS ARE FOUND 



conditions may have existed in our latitudes when there was a very different proportion 

 between land and water. Following up the important observations of Humboldt and 

 Lyell, upon the influence of continental masses and great seas upon climate, Mr. Darwin 

 materially adds to the cumulative proofs, that temperature is not dependent solely upon 

 latitude. 



Thus, the conditions of the difficult problem which we have to solve are now much 

 more fully brought before us than in any former discussion of the subject. We have 

 in running water a power, the extent of which has, however, yet to be worked out. 

 We have also a vera causa in the icefloe, which, it appears to me, goes much further 

 towards explaining the difficulty, than any hypothesis which has yet been framed ; al- 

 though it would, perhaps, be premature to assert that it completely settles the question, 

 still less that such agency can be considered the only one by which bowlders may have 

 been transported. 



It still remains for us to say a few words on the present relative heights at which the 

 bowlders occur, although, if their deposit by icefloes be admitted, much difficulty is 

 obviated, as the bottom of a sea in which the bowlders were dropped, may have often 

 been so full of inequalities, as to present, when desiccated, an outline similar to many 

 of our undulating and even hilly countries. But the striking and sudden differences of 

 altitude at which these blocks and shells are found, in the same district, seem to call for 

 additional explanation. The difference of height between the top of Moel Tryfan, 

 and the plains of Salop and Cheshire (1400 to 1600 feet), is almost too great to 

 admit of the supposition that such was the submarine surface. If, indeed, we admit 

 that in this district, such vast submarine inequalities existed, still we should have to 

 account for others of much greater amount in foreign countries 1 ; and, therefore, it is 



1 Illustrating the apparently inexplicable position of certain bowlders in relation to tbe present outlines of 

 the earth's surface, I would cite one of many cases which have fallen under my observation in and upon the 

 flanks of the Alps. 



N. 



Alps .. , 



och.) HO. 



) h 



S. Central chain of Alps. 



Bavaria. 



This wood-cut represents a transverse section across the Tyrolese mountains which flank the valley of the 

 Inn west of Inspruck. To the south, the older transition rocks (c) are flanked by the granitic nucleus of the 

 chain (d). To the north are the great masses of limestone (b) (crystalline and dolomitic), which representing 

 our oolitic series and lias, attain heights of 6000 feet above the sea, and beyond them the lower hills of green 

 sand (a) and tertiary deposits of Bavaria. In one of the loftiest combs of the Alpine limestone, called Hogel- 

 poch, considerably above Seefeld, and at a height of at least 3000 feet above the valley of the Inn, is an ac- 

 cumulation (*) of blocks of gneiss, granite, porphyry, chlorite slate, &c, materials which can have been derived 

 only from the central mountains (c and d), and from which they are now completely cut off by a deep valley. 

 My present belief is, that there was a period in which the blocks in the valley and those on the summits of the 



