1862.] 



41 



district through which the valley passes ; thnt 

 only the Seine valley contains granite from the 

 Morvan, the Oise slate-rock debris from the Ar- 

 dennes, the Marne nothing older than oolitic 

 debris, whilst the Therain and the Somme valleys 

 contain nothing but debris of the chalk and ter- 

 tiary strata. The same rule applies to the English 

 area ; but the fact is not so apparent, owing to 

 various conflicting elements pointed out by the 

 author who shows, by a map of the two coun- 

 tries, how great are the range and spread of these 

 beds, and how large a proportion of our drift- 

 gravels are of fluviatile origin. 



The High-level Gravels. From the facts re- 

 corded by the several independent observers 

 abroad, and from his own observations in this 

 country, the author arrives at a general proposi- 

 tion illustrated by the accompanying diagram, 

 which shows, 1. D, a major valley or plain of 

 denudation anterior to the excavation of the river- 

 valley. 2. e, anon-fossiliferous drift on the slope 

 and base of D. 3. C, the river- valley. 4. d, the 

 high- and c, the low-level gravels. 5. , recent 

 alluvium. 6. A, the present river-channel. 



The high-level gravels (d) appear on both sides 

 of the valley, and their connexion before the ex- 

 cavation of C is pointed out. This is one of the 

 points insisted upon by the author ; the two 

 having been generally considered as contempo- 

 raneous, or even sometimes the higher-level de- 

 posits as newer than those of the lower level. It 

 is to be observed that the phenomena here re- 

 ferred to relate to broad valleys, and not merely 

 to river-channels. 



The loess is not shown in the diagram, other- 

 wise the section represents the condition of the 

 case on the supposition that all the parts are 

 complete. But this rarely happens. Some low- 



