RECAPITULATION. 309 



here and there receive angular flints and shells brought down 

 from the hills in a more or less transverse direction by the 

 rivulets after heavy rains. 



Mr. Prestwich regards the difference of level between the 

 upper gravels and the loess as "a measure of the floods of 

 that period/' If the gravel beds were complete, this would 

 no doubt be the case ; but it seems to me that the upper-level 

 gravels are mere fragments of an originally almost con- 

 tinuous deposit, and under these circumstances the present 

 cannot be taken as evidence of the original difference. 



As the valley became deeper and deeper the gravel would 

 be deposited at lower and lower levels, the loess always 

 following it;* thus we must not consider the loess as a 

 distinct bed, but as one which was being formed during 

 the same time, though never at the same place as the 

 beds of gravel. In fig. 142 I have given a diagram, the 



Fm. 142. 



CHALk 



Diagram to show the Relations of the Loess and the Gravels. 



better to illustrate my meaning; the loess is indicated by 

 letters with a dash and is dotted, while the gravels are repre- 

 sented as rudely stratified. In this case I suppose the river 

 to have run originally on the level (1), and to have 

 deposited the gravel (a) and the loess (a!) ; after a certain 

 amount of erosion which would reduce the level to (2) ? 

 the gravel would be spread out at (), and loess at (&'). 

 Similarly the loess (c r ) would be contemporaneous with the 

 gravel (c). 



* See Mr. Prestwich's paper read before the Koyal Society, June 19th, 1862. 



