1862.] 171 



Reference is first made to the Loess of the valley of the Rhine, 

 and the author accepts Sir Charles Lyell's explanation that it is the 

 result of a river-deposit ; but he does not agree in the explanation as 

 to the mode which led to the actual results, so far as the present 

 district is concerned. 



One difficulty in understanding the spread of the loess in England 

 and France has always been the greatly different levels on which it 

 occurs, being present in the bottom of the valleys, and occurring on 

 ground 100, 200, and 300 feet higher. This evidently places it 

 beyond the reach of inundations with the valleys formed as they are 

 at present, and the prior origin of which the common covering 

 of loess might lead one at first to infer. But if, instead of start- 

 ing at the present low levels, the valleys be taken at the level the 

 author showed them to have had at the period of the upper high- 

 level gravels, it will give a base for the original river-levels of 100 to 

 200 feet above the existing valleys, and therefore it will reduce the 

 difference of level of the higher deposits of loess to be accounted for, 

 to 100 or 150 feet. In many cases it is less, but it is still consider- 

 able. It thus brings the whole of the loess within the possible range 

 of inundations of the old Post-pliocene rivers at different periods of 

 their age ; the higher beds of loess having been deposited during 

 floods at an early period, and before the excavation of the present 

 river- valleys, and the lower beds having been deposited after the ex- 

 cavation of the valley, and while some of the old meteorological con- 

 ditions still prevailed. 



The author shows that the loess is, in fact, like the high- and low- 

 level gravels, always connected with river- valleys, although it extends 

 much beyond the limits of these beds, rising to much higher levels, 

 and extending far beyond their limits. He then shows that in the 

 valley of the Somme, the difference between the highest levels of the 

 loess and the upper gravels thus becomes reduced to 60 or 80 feet ; 

 in the Oise, to apparently about 50 feet ; in the Seine valley, to 

 about 120 to 150 feet ; and in the Bresle valley to 70 feet. 



The loess contains the same mammalian remains and the same 

 species of land mollusca as the gravels. Of freshwater mollusca it 

 contains hardly any. 



Notwithstanding the extension of the loess over the higher grounds 

 flanking the river-valleys, still such grounds are always bounded by 



