CLASSIFICATION OF RIVERS 131 



on an uplifted, slightly tilted peneplain or plain of subaerial denuda- 

 tion. Streams originating on a newly ice-scoured surface may be 

 noted as of this class, but of minor importance. If surfaces of purely 

 marine denudation are of sufficient extent to have streams originate 

 on them on elevation, these would also be classed here. Finally, 

 consequents arising on a surface of deformation include several 

 types : those formed on a simple dome, those formed on a series of 

 anticlines and synclines, and those formed on tilted fault blocks. 

 In the first case we have radial consequents of the n^'' + i order 

 tributary to another consequent of the n*'^ order which may be the 

 first (principal consequent) or any higher order. In rare cases 

 domes of deformation rise directly out of the sea, when the radial 

 consequents are of the first order, n being zero. In the anticlinal 

 and synclinal folds we have transverse consequents flowing down 

 the limbs of the anticline, and longitudinal consequents flowing in 

 the synclines. The first belong to the n*'^ -(- i order, the second to 

 the nt'\ In exceptional cases a transverse consequent may flow into 

 the sea, the shore of which may be formed by an anticline, or the 

 syncline may be filled by an arm of the sea or by a lake. Conse- 

 quents flowing down the back slopes of inclined fault blocks are in 

 all essentials like those flowing down the limbs of anticlines. 



B. Extended consequents are streams of an older type which 

 become extended across the newly emerged coastal plain. These 

 streams do not dififer from those originating on the coastal plain, 

 except in their greater volume of water and hence greater erosive 

 power. They will, therefore, cut deeper than the others, becoming 

 the master streams of their respective regions, and directing to a 

 large extent the further development of their drainage system. 

 Streams extended across a dry delta may also be classed here, as 

 are those extended across a plain of glacial deposition. In so far 

 as the older part of the stream is concerned it may be simple or 

 complex, monogene or polygene. 



C. Inherited consequents. These are consequents which are 

 superimposed upon a complex terrane by learning to flow upon a 

 coastal plain which once covered the complex rocks, and which 

 directed the course of the river, though long since removed by 

 erosion. Superimposed consequents are believed to be illustrated 

 by the lower courses of the Housatonic and Connecticut rivers in 

 southern New England. The coastal plain strata which apparently 

 once extended over this area have been entirely removed by erosion. 

 (Dodge-i2.) The coastal plain strata may be replaced by layers of 

 volcanic ash (Gunnison River), by drift, by river, or eolian deposits, 

 or, in exceptional cases, by glacial ice. 



