vertical measure of strength »>.• ^reat . : so soon as a stream 

 becomes of negligible depth, so soon does it lose its corrasive 

 power either in a vertical or lateral direction. From a 

 consideration of these various points it may be shewn that 

 the tendency of a stream is to develop a flattish floor to its 

 channel, the width of such floor bearing a definite relation 

 to the volume and velocity of the stream. That is to say 

 a valley floor formed by a glacier of a definite size is not 

 adjusted to the needs of any other glacier of different 

 volume then the whole channel will be widened symmetri- 

 cally and the old profiles will be removed altogether. If 

 we reduce the volume, the new glacier will not be able to 

 utilise the old floor in its entirety, but will proceed first to 

 iill up the greater irregularities of channel form and then 

 to excavate a narrower but similarly shaped channel along 

 the floor of that which had been determined by the greater 

 volume. 



Similarly during this stage smaller "steps" and smaller 

 cirques will be developed within the older and larger 

 examples. It is evident that a large glacier must produce 

 a much greater channel than thai produced by a stream of 

 lesser volume, even if of much greater mobility. A 

 moment's reflection would thus be sufficient to convince 

 those who deny the efficacy of ice as a rock corrader, that 

 the peculiar floors of hanging valleys (of Alpine Regions) 

 of cirques, and the "treads" of •'steps" could not be used 

 as channel Moors in their entirety bv the ordinary water 



stages of attack. It would le ;, mei-iiu iiic;l impossihil 

 for any water stream in California, to utilise the wholt 

 the lower 2,000 feet of the Yoseraite as a channel, and s 

 appeal to ordinary stream action as having formed I 



