OF DENISON UNIVERSITY. 



31 



filled for the location of an eroded col and yet the peculiar topographic 

 form has been produced in an entirely different manner. 



In the case in which the new system carries a larger or smaller 

 volume of water but has not as yet reached the depth of the old system, 

 or in other words when the new system is larger or smaller but above 

 the old, the location of the col is partially indicated by the broadening 

 of the valley and the descent of the rock floor of the valley in oppo- 

 site directions from the col. Other adjacent streams usually indicate 

 also the position of the divide in which the col occurred. These con- 

 ditions may exist where there has been a modification and reversal of 



drainage without there ever having been a col at the point suggested 

 by the data and the divide which at first would seem, from map study, 

 to be a part of the old form is in reality a result of the combination of 

 the two forms. The conditions would be produced when one large 

 drainage hne is developed transverse to another with a reversal of part 

 of the old system and an increase in the volume of water ( or lapse of 

 considerable time). The relations are indicated diagramatically in the 

 accompanying figure in which the old drainage is indicated by the con. 

 tinuous wavy lines ; the new drainage, by the dotted wavy lines. 



The form at A resulting from this combination I have termed a 

 pseudocol from the fact that the data so strongly indicates the existence 



