this also implies the necessity for the stream strength to 

 decrease in a similar ratio upon decrease in velocity. 

 The latter is the main point which has been neglected 

 hitherto in discussions upon glacial erosion. 



From the foregoing it is evident that all streams follow 

 the thalwegs of each other as opportunity offers. In the 

 case where a younger stream is too large to be wholly con- 

 tained in a channel of an older stream, then the thalweg, 

 however, may be seen to be the location of maximum 

 stream energy. 



We are now in a position to discuss the energy of a 

 stream in its relation to corrosion. Although the kinetic 

 energy increases as the product both of the cube of the 

 velocity and the increase of the cross-section, nevertheless 

 there are the three directions to be considered along which 

 this energy may be expended. These are the vertical, 

 longitudinal and lateral directions, all perpendicular to 

 each other and along each of which the e 

 in a certain proportion. 



Let OA, OI 





