THE POI-ISriED ROCKS OF ROCHESTER. 



265 



might, indeed, be a small accumulation of earthy materials on 

 the side, from the tendency to slide sideways from the front ; but 

 this effect must be relatively small. We cannot, therefore, make 

 application of this theory with much safety to the waved form of 

 portions of the earth, or those sudden elevations and depressions 

 which are so common in our country. To refer to no others than 

 thos(! presented in Prof. Ilitchc-ock's Geology of Massachusetts, 

 ought not other evidence than the mere existence of the form of 

 the surface to be re(iuired ? According to Agassiz, an examina- 

 tion of the moraines in the Alps would prove their composition 

 such as the theory supposes, rough and angular blocks of the 

 rocks mixed in confusion with the finer materials. Similar proof 

 should be obtained before it can be reasonably maintained, that 

 such appearances are in truth moraines. The dashing of mighty 

 waters, with their reaction, might leave the sand and gravel in 

 the peculiar fonn which these supposed moraines present, and the 

 whole result be that of diluvial action. In this section of the 

 country are such appearances on a great scale ; but in many in- 

 stances, the composition of them, the sand and gravel, finer and 

 coarser, and in regular layers, has been so far exhibited at their 

 base, and on their sides, or towards their top, that there can be 

 no doubt about them. It is lamentable that Geology has 

 so often earned the application of favorite hypotheses to a ruin- 

 ous extent. 



To the polishing of the surface there is not the same difficulty 

 in the application of the theory ; for Agassiz shows, that the pol- 

 ishing actually takes place under the glacier, and this effect, the 

 polished surface, actually exists under our feet. The rock chiefly 

 polished here is the limestone above the calciferous slate of Eaton, 

 iiard, slightly granular, pretty compact, and bituminous. In a few 

 places, the geodiferous lime-rock on this, is the polished stone, but 

 is here only a thin layer, while the other is a thick stratum. The 

 polished surface is found in many places in the city on both sides 

 of the Genesee, so that many acres are polished sometimes forty 

 rods in length ; just west of the city are a hundred rods un- 

 covered, and in other places ten rods, four rods or a few feet 

 only in length, but in different directions, making it highly 

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