208 THE PHENOMENA OF DRIFT, OR 



but more commonly there is only one terrace besides the bank. 

 So far as I have observed, they almost always occur where there 

 is a considerable expansion of the banks of the stream, and more 

 or less of a gorge exists at the lower extremity of the basin through 

 which the stream issues. I find Connecticut river to be thus ter- 

 raced through almost its whole course, in numerous separate 

 basins. PI. VIII, fig. 14 shows these terraces, as they appear in 

 Wethersfield, Vermont, seen from the opposite side of the river 

 in Claremont. 



Whatever may be the fact in regard to similar terraces at the 

 mouths of rivers, where they are exposed to the action of the sea, 

 it is clear that those in the interior must have been mainly pro- 

 duced by the waters of the river itself. For even if we admit 

 the land to have been once low enough to bring every successive 

 basin along a river upon the coast, yet the barrier at the low^er part 

 of the basin must have prevented an influx of the waves suffi- 

 cient to wear away the softer deposits that bordered on the river. 

 And I conceive that the waters of the river are sufficient to pro- 

 duce the existing terraces, if we only suppose, what no one will 

 deny, that they gradually wear down their barriers. Nor do I 

 conceive that the river must lower its bed by sudden and suc- 

 cessive vertical movements of the land, or tlie water, in order to 

 produce terraces. As to the manner in which the river might 

 produce them by its ordinary movements, I must refer to my Final 

 Report on the Geology of Massachusetts, since the description 

 would be too long to inti-oduce in this place. 



But whatever theory we adopt as to the mode in which these ter- 

 races have been formed, nearly all will admit that the work began 

 when the waters that deposited the clay and sand above the cbift, 

 had so far retired, whether by the upheaving of the surface, or the 

 subsidence of the waters, that the upper ten-ace of the rivers was 

 left bare ; and that the work has continued nearly to tlie present 

 time. Dr. Buckland supposes them to be the result of lakes, 

 formed by moraines ; and that they were gi'adually formed as the 

 barriers of those lakes were cut through. If this be a correct view^ 

 we cannot regai-d these terraces as belonging to the period of drift 

 exclusively ; but as reaching also into the alluvial period : indeed, 



