CORRASION BY GRAVITY STREAMS. 321 



Conclusions— A. Inductive Studies. 



(1) Cirques, hanging valleys, rock basins, facetted spurs 

 (orspurless walls), smoothed cols, "steps" and "treads" 

 occur in all recently glaciated regions. 



(2) In proportion to the intensity of the recent glaciation 

 so are these peculiar land profiles pronounced in number, 

 size, and appearance. 



(3) In localities not glaciated recently such peculiar land 

 profiles are absent. 



(4) All these forms are matched in miniature along any 

 channel determined by thunderstorm waters. 



(5) Along the beds of even large stream channels similar 

 forms occur to those just enumerated. 



(6) The forms in all these cases are similarly situated 

 with respect to their enveloping channels. 



(7) The forms in each case are adjusted to the size of the 

 various stream volumes (whether ice or of water) known 

 to have been associated with them. 



B. Deductive Studies. 



(1) All streams in nature are due primarily to pressure 

 as weight. 



(2) The path of any stream particle tends to the para- 

 bolic form. 



(3) All must seek the lines of least resistance; and inas- 

 much as a vertical force (gravity) determines the flow, the 

 lines of least resistance will be the lines of quickest descent 

 for streams. 



(4) All streams therefore tend to follow the thalwegs of 

 each other as opportunity arises. 



(5) Increased pressure as weight implies the increased 

 mobility or velocity of a stream. 



