Art. I.J Clakk, Drainage Modifications 5 



of the Walhonding drainage. Of course there are the usual 

 indications of piracy from one side of the ridge to the other, 

 but only very limited areas are affected by any of these cases. 

 Many of these piratical modifications, however, are of sufficient 

 magnitude and local interest to repay well the time that would 

 be required to work them out carefully. The discovery of the 

 high and unbroken character of the ridge between these two 

 streams demolished what had been considered the most im- 

 portant of our working hypotheses. However the fact had 

 been demonstrated beyond a peradventure, so a new turn was 

 taken and the possibility observed that perhaps one of the two 

 cols that had been located on Owl and Mohican Creeks had not 

 been based on sufficient data. Professor Tight had located 

 these cols some two years previously, and in order that the 

 work might be reviewed with as little bias as possible, it was de- 

 cided that the writer, who had not been on the ground before, 

 should make a trip into that region. Professor Tight suggested 

 in a letter that probably no eroded col would be found on the 

 Mohican. The writer's opinion was that none would be estab- 

 lished on Owl Creek. In the sequel it was demonstrated that 

 both suggestions were untenable and the original inferences the 

 only ones that could be supported by the evidences of the field. 

 Leaving the old Mt. Vernon River at the little village of How- 

 ard, Owl Creek enters the mouth of a pre-glacial valley which 

 gradually narrows and whose rock floor gradually rises as Mill- 

 wood is approached. In the lower portion of this valley its 

 floor is covered to an undetermined depth with bowlder clay, 

 and at a point a mile or such a matter frt)m Howard the valley 

 is filled more than half way across with a heap of morainic ma- 

 terial rising 50 feet or more above the level of the present val- 

 ley floor. As one approaches Millwood the glacial drift thins 

 out so that there is left but a comparatively shallow stratum of 

 soil on the rock floor of the old valley, and the creek itself has 

 cut a gorge into this rock floor. The maximum depth attained 

 by this gorge probably does not exceed 40 feet. This maximum 

 depth of gorge, accompanying the maximum elevation of the 

 old rock floor, occurs perhaps a mile East of Millwood. From 



