290 ON THE PARTICULAR ORDER OF 



conglomerate rocks, fine red sandstone, shales, clays, 

 and marls, and especially remarkable for including 

 gypsum and rock salt. 



The magnesian limestone and the red marl are 

 associated by some English Geologists, under the 

 name of a formation ; and in a similar way, all the 

 strata, of whatever nature, consisting of various lime- 

 stones, sandstones, shales, and clays, which lie be- 

 tween the last described bed and the ferruginous sand, 

 are united in a similar group, by the name of the 

 oolithe formation. I must refer to the authors them- 

 selves, and particularly to Conybeare, for all points 

 of a local and minute nature ; and shall here merely 

 give the principal beds as they are enumerated, where 

 the series is most complete. 



I ought still however to remark, that not only is 

 this principal formation divided into three, viz., a 

 lower, a middle, and an upper one, but that there 

 are even inferior subdivisions, since the lias, for 

 example, is itself a series and not a single rock. 



The first which thus follows is, in England, known 

 by the name of Lias, and it consists of limestone of 

 various characters, in numerous beds, alternating 

 with clays and shales. It contains a great variety of 

 organic remains, chiefly marine, with some very re- 

 markable amphibious animals, of extinct genera and 

 species. 



It is here but justice to the general reader to state, 

 that all those geologists who have investigated the 

 English strata, have not agreed in their manner of 

 grouping the inferior beds. At this particular point, 

 for example, certain marls, clays, and sands, have, 

 by some, been thrown into a group distinct from the 

 beds, and inferior to the next rock, or the oolithe ; 

 while, by others, the clays are enumerated as be- 



