130 PRINCIPLES OF STRATIGRAPHY 



dents brought about by outside agencies, become polygenetic, i. c, 

 become a union of originally separate rivers, but all of them begin 

 as simple types. 



Simple or Monogene Rivers. 



Five simple or monogene types can be recognized. I. Conse- 

 quent streams, II. Insequent streams, III. Overflow streams, IV. 

 Glacial streams, V. Subterranean streams. 



I. Consequent Streams. These are the streams which come 

 into existence upon a new land surface. Such a land surface may 

 be young or rejuvenated, but so far as the river is concerned, it is 

 a new land. The mode of origin may be A. by origination (de 

 novo), B. by extension, and C. by inheritance. In all cases the 

 consequent is distinguished from the insequent type by the fact 

 that it starts upon a sloping land surface and cuts primarily 

 downward rather than headward, although this latter also occurs. 

 From the other types it is distinguished by not having primarily a 

 stored supply at its head, as in the overflow river from a lake, or 

 in the stream supplied by the melting of a glacier. Its supply of 

 water is derived from the run-off and the ground water. 



A. AVtc'/v originated consequents may be classed as principal 

 and as tributary, the former entering the sea or receiving basin 

 direct, the others being tributary to other consequents, which may 

 or may not be principal ones. Calling the principal type the conse- 

 quent of the first order, its consequent branches would be those of 

 the second order, their consequent branches would represent the 

 third order, and so forth. These streams may next be divided 

 according to the type of land they come into existence on, the three 

 types being: i. Constructional surface consequents, 2. Destruc- 

 tional surface consequents, and 3. Deformational surface conse- 

 quents. The consequents arising on constructional surfaces may 

 be divided into (a) coastal plain consequents, or those originating 

 on a newly emerged coastal plain, elevated by purely epeirogenic 

 movements of the land or by negative eustatic movements of the sea, 

 or by the drainage of an elevated water basin; (b) fan delta conse- 

 quents, or those originating on dry deltas of other streams or on 

 landslides; (c) moraine and till surface consequents, or those com- 

 ing into existence on a sloping surface of deposition of glacial 

 detritus; and (d) lava and volcanic cone consequents, or those orig- 

 inating on the slopes of volcanoes or on lava flows. Consequents 

 arising on a surface of destruction, upon simple elevation, are almost 

 wholly represented by peneplain consequents, i. e., those developing 



