218 



Scientific Geology. 



by the Connecticut, three miles above, and nearly a mile below Tur- 

 ner's Falls, of which a sketch will be given in treating of greenstone, 

 presents a good example for examination. The coarser varieties, 

 however, are not so abundant here, as at Mount Toby in Sunderland. 

 On the west side of Connecticut river, opposite Sunderland, Deerfield 

 mountain exhibits nearly every variety of the lower beds of the for- 

 mation. Let the observer pass to the east bank of the river at Whit- 

 more's ferry, three miles north of Sunderland village, and he will 

 land upon a ledge of the coarsest conglomerate that has just been de- 

 scribed. Lying directly above this, and, dipping a few degrees easter- 

 ly, as do all the strata of Mount Toby , he will find the black bitumin- 

 ous shale containing impressions of fish; 10 feet thick. Immediate- 

 ly above this succeeds a coarse conglomerate, scarcely differing from 

 that beneath, and forming a mass 200 or 300 feet thick. Proceeding 

 southeasterly to the top of Toby, not less than 900 feet above the river, 

 he will find numerous alternations of the coarsest conglomerates with 

 the finest red and grey sandstones; or rather shales. And the passage 

 from one variety to the other is not in general gradual, but sudden ; 

 so that the line between the finest and coarsest materials is well mar- 

 ked. 



It is very obvious, in such cases, that the finer layers of the rock 

 must have been deposited in still waters, and the coarser materials 

 have been the result of powerful abrading currents. And I know 

 not a more difficult point in the theory of the earth, than to explain 

 the cause of so many and so sudden changes from motion to rest and 

 from rest to motion, in the waters in which such rocks were formed. 

 The facts might perhaps be explained by supposing these deposites to 

 have resulted from the long continued action of a river, carrying 

 into the bottom of a lake or the ocean, coarser materials during 

 its floods, and the finer sediment at low water : But the different na- 

 ture of the materials composing successive layers of the conglome- 

 rate strata, show that the current must have swept over and torn up va- 

 rious rocks at different times : and consequently must have come from 

 various directions at successive periods ; except perhaps in those rare 

 cases, where it wore away the higher formations entirely. Now we 

 cannot conceive how any river should be made to pass over rocks 

 so different as we find in the alternating beds of Mount Toby, at dif- 

 ferent periods : it would require alterations in its bed, almost without 

 number. 



There is, however, one other mode of accounting for the facts in this 

 case, which may perhaps be thought more satisfactory. It seems to be 



