CHAP. xvi. THE LOESS IN BELGIUM. 331 



derived from the disintegration of the crystalline rock, which 

 must have decomposed in the atmosphere before the mud 

 had reached this height. Entire shells of Helix, Pupa, and 

 Sucrinea, of the usual living species, are embedded in the 

 granitic mixture. We may therefore be sure that the valley 

 bounded by steep hills of granite existed before the tranquil 

 accumulation of this vast body of loess. 



During the re-excavation of the basin of the Ehine succes 

 sive deposits of loess of newer origin were formed at various 

 heights ; and it is often difficult to distinguish their relative 

 ages, especially as fossils are often entirely wanting, and the 

 mineral composition of the formation is so uniform. 



The loess in Belgium is variable in thickness, usually 

 ranging from ten to thirty feet. It caps some of the highest 

 hills or table-land around Brussels at the height of 300 feet 

 above the sea. In such places it usually rests on gravel, and 

 rarely contains shells, but when they occur, they are of recent 

 species. I found the Succinea oblonga, before mentioned, 

 p. 327, and Helix hispida in the Belgian loess at JSTeerepen, 

 between Tongres and Hasselt, where M. Bosquet had pre 

 viously obtained remains of an elephant referred to E. primi- 

 genius. This pachyderm and Rhinoceros tichorhinus are 

 cited as characterising the loess in various parts of the valley 

 of the Rhine. Several perfect skeletons of the marmot have 

 been disinterred from the loess of Aix-la-Chapelle. But 

 much remains to be done in determining the species of mam 

 malia of this formation, and the relative altitudes above the 

 valley-plain at which they occur. 



If we ascend the basin of the Neckar, we find that it is 

 filled with loess of great thickness, far above its junction with 

 the Rhine. At Canstadt near Stuttgart, loess resembling 

 that of the Rhine contains many fossil bones, especially those 

 of Elephas primigenius, together with some of Rhinoceros 

 tichorhinus, the species having been lately determined by 



