230 Royal Society:— 



On the other hand, along the outer bank there will be a general 

 tendency to descent of surface-water which will have a high velo- 

 city, not having been much impeded by friction ; and this will wear 



away the bank and carry the worn substance in a great degree down 

 to the bottom, where, as explained before, there will be a general 

 prevailing tendency towards the inner bank. 



Now, further, it seems that even from the very beginning of the 

 curve forward there will thus be a considerable protection to the 

 inner bank. Because a surface stream-line C D, or one not close to 

 the bottom, flowing along the bank which in the bend becomes the 

 inner bank, will tend to depart from the inner bank at D, the com- 

 mencement of the bend, and to go forward along D E, or by some such 

 course, leaving the space G between it and the bank to be supplied 

 by slower-moving water which has been moving along the bottom of 

 the river perhaps by some such oblique path as the dotted line F G. 



It is further to be observed that ordinarily or very frequently 

 there will be detritus travelling down stream along the bottom and 

 seeking for resting-places, because the cases here specially under 

 consideration are only such as occur in alluvial plains ; and in 

 regions of that kind there is ordinarily*, on the average, more de- 

 position than erosion. This consideration explains that we. need 

 not have to seek for the material for deposition on the inner bank 

 in the material worn away from the outer bank of the s;?me bend 

 of the river. The material worn from the outer bank may have to 

 travel a long distance down stream before finding an inner bank 

 of a bend on which to deposit itself. And now it seems very clear 

 that in the gravel, sand, and mud carried down stream along the 

 bottom of the river to the place where the bend commences, there 

 is an ample supply of detritus for deposition on the inner bank of 

 the river even at the earliest points in the curve which will offer any 

 resting-place. It is especially worthy of notice that the oblique 

 flow along the bottom towards the inner bank begins even up stream 

 from the bend, as already explained, and as shown by the dotted 

 line F G in fig. 3. The transverse movement comprised in this 



* That is to say, except when by geological changes the causes which have 

 been producing the alluvial plain have become extinct, and erosion by the river 

 has come to predominate over deposition. 



