Gilbert, Jukes, Davis and others, that ordinary river chan- 

 nels such as those of the Thames and the Amazon have 

 been developed by their contained streams, and it has also 

 been shown by Gilbert, that the form of the channel shows 

 that it is the flood and not the normal stream which does 

 the work of channel formation. Now all this is easily 

 understood, because the action of both flood and normal 

 water streams falls within the experience of every observer. 

 But let it be supposed that certain cosmopolitan agencies 

 had caused periodic and long continued floods, say once 

 every 100 years. Then suppose some intellectual beings 

 with ephemeral existences only to become interested in the 

 origin of ordinary stream developed valleys. Not one of 

 them had ever seen a flood, nor had there been any record 

 of a flood since they had commenced scientific investiga- 

 tions. They would naturally be at a loss to account for 

 the deep rock basins, the cutting curves and the general 

 width of the channels, seeing that at these spots the normal 

 streams appeared to be least active. After a time some 

 one might draw attention to the huge heaps of debris among 

 and through which the normal stream bubbled at one place 

 and became dammed in another to form ponds. The idea 

 of the existence of former floods would now be suggested 

 and generally adopted. At this stage someone might be 

 emboldened to announce a flood origin for the larger 

 channel profiles, such as the rock basins and the main 

 cutting curves, but this idea would be received with dis- 

 favor because no one had seen the action of a flood, and 

 inasmuch as the water in the deep pools of the channel 

 appeared to occupy the exact spots where the stream 

 revealed its least competence, so would it seem utterly 

 ridiculous to expect these spots to have been the sites of 

 maximum energy simply as a result of increasing the stream 

 volume. Of course such a conclusion would not be reached 

 from a consideration of dynamical principles, but simply 



