796 THE GEOGRAPHICAL SIGNIFICANCE OF FLOODS, 



ing stream corrasive effects 1 Whichever is taken, the problem 

 resolves itself into a summation of excessively numerous and 

 relatively small activities. Is the valley the summation mainly 

 of many thousand flood- thrusts; or is it rather the " integration 

 of an infinity " of normal and drought stream effects ? 



If now it can be shown that floods of great strength produce 

 characteristic and important forms in valley channels; and 

 furthermore that these characteristic and dominant forms remain 

 virtually unaltered until the return of an equally great, or still 

 greater, flood, we should obviously feel inclined to assign b}^ far 

 the more important corrasive effects to flood-action. 



Moreover, if a study of very small flood-channels, such as road- 

 side storm-gutters and brooklets; of larger examples such as 

 those of rivers and shorelines; and of mighty channels also such 

 as Alpine and Sierran canons, channels undoubtedly subject to 

 former intense glacial action — if a study of these, we say, should 

 reveal, in each type, the presence of peculiar and prominent 

 contours all of similar shapes; and not onl}^ so but a similarity 

 of situation in each case for such contours, the difference in size 

 being the only essential point of distinction; and furthermore 

 the size being in direct proportion to the size of the various 

 floods — then indeed we might reasonably feel much more 

 strongly supported in our contention. We would be prepared, 

 of course, to admit the corrasive properties of streams in 

 their normal or even in their drought stages; nevertheless, since 

 the flood-contours are only seriously modified, or possibly effaced, 

 by other deluges, land-reduction would appear to be virtually 

 accomplished by gread flood-corrasion.* 



Thus if this simple principle be grasped, it will at once be 

 seen how geographical methods will be revolutionised. For 

 seeing that shorelines, stream-developed valleys and fiord-contours 

 are the work of comparatively Titanic forces, it would be useless 

 for one to study the methods of the harmless drought-stricken 



* Similarly for land-reduction by wind-action, the work of the great wind- 

 storm should altogether overshadow the effects of the intergale and the 

 zephyr stages. 



