Geology and Min6ralogy. 8T 



volumes (whether ice or water) known to have been associated 

 with thera. 



" B. Inductive Studies. — (1) All streams in nature are due pri- 

 marily to pressure and weight. (2) The path of any stream par- 

 ticle tends to the parabolic form. (3) All must seek the lines of 

 least resistance, and inasmuch as a vertical force (gravity) deter- 

 mines the flow, the lines of least resistance will be the lines of 

 quickest descent for streams. (4) All streams therefore tend to 

 fellow the thalwegs of each other as opportunity arises. (5) 

 Increased pressure as weight implies the increased mobility or 

 velocity of a stream. (6) Increased velocity implies corrasive 

 action rising in a high geometrical ratio. (7) From the forego- 

 ing the profiles of all stream channels formed individually by one 

 stream type only should therefore be similar in general appear- 

 ance. (8) The forms developed by the general stream have been 

 worked out bj'^ means of these principles. (9) But the forms 

 deduced for the general stream are matched in nature in the case 

 of the ordinary water stream (which has been definitely observed 

 moreover to have formed its own channel profiles). (10) There- 

 fore any group of such similarly shaped, similarly situated, and 

 similarly associated profiles as those deduced for the general 

 stream can be satisfactorily explained by stream action. (11) 

 But such groups of forms occur in regions of recent glaciation. 

 (12) They can be satisfactorily explained, therefore, by stream 

 action. (13) Moreover, glaciers themselves are streams. (14) 

 Glaciers in recent times occupied the same general relations (as 

 to size, surface, and so on) to cirques, lake basins, over-deepened 

 valleys, and other associated forms which the general stream type 

 has been deduced to occupy with regard to its own channel forms. 

 (15) With the exception of a glacier no other stream in these 

 glaciated regions is known which had the power to fashion the 

 typical cirque, rock basin and spur "facet." (16) Glaciers there- 

 fore, in all probability, formed the typical cirques, the fiord and 

 Alpine basins, the spurless chasms of Alpine regions, as also the 

 hanging valleys and the "steps" and "treads" in Alpine valleys. 



" C. Apparent Lack of Ice Gorrasion as Evidenced by a Study 

 of Present Glaciers. — The channel form is adjusted to the strength 

 of the stream. Upon a reduction of stream volume a readjust- 

 ment of the channel grade is set up, and the stream appears most 

 inert at the locations of the maximum energy exerted by the 

 larger stream. This is the case with present-day glaciers. The 

 recent ice-floods formed cirques, rock basins, and other forms 

 adjusted to their own size and strength, while the deglaciated 

 valleys of to-day evidence the very recent retreat of the last ice 

 flood. The channel grade, therefore, must now be readjusted. 

 This being so, morainic material must fall out along the old cut- 

 ting curves, and the ice generally must be most inert at spots 

 like fiords and lake basins. This explains the apparent anomaly 

 otherwise of the association of inert and banded glaciei's with 

 cirques and rock basins, and the occupation of old ice-cutting 

 curves by moraines." h. e. g. j. b. 



