122 Mr Lyell on the Loamy Deposit of the Rhine. 



existed, for those waters must have been at rest from which 

 the loess, with its unbroken shells, was thrown down as sedi- 

 ment. Probably the relative levels of different parts of the 

 country now covered by loess, have been altered by the eleva- 

 tion of some tracts, and the depression of others, since the loess 

 was formed. In order to possess data for speculating on this 

 point, we must have more accurate observations on the highest 

 levels which the loess ever attains above the Rhine and above 

 the sea. 



This singular formation is so homogeneous in its mineral 

 character, whether it rests on gravel, volcanic matter, granite, 

 red sandstone, or any other rock, that it cannot be compared to 

 the local alluviums which different rivers and torrents may have 

 produced in various parts of the same hydrographical basin. It 

 may not all have been deposited at one time, or in one vast lake ; 

 but it seems to have been derived from some common source, as 

 from the sediment of one great river like the Rhine, continuing 

 to overflow a certain district, and always bringing down the same 

 kind of sediment. 



I subjoin a list of the fossil shells which I collected myself, 

 from the loess of the various districts which I have mentioned 

 in this paper. 



