250 THEORY OF THE EARTH. 



Under the chalk are found deposits of green 

 sand, of which its lower strata contains some orga- 

 nic remains. Beneath this are ferruginous sands. 

 In many countries both of these deposits are agglu- 

 tinated into heds of sandstone, in which lignites, 

 amber, and remains of reptiles, are also observed. 



Under this, we find the great mass of strata 

 which compose the Jura chain, and that of the 

 mountains by which it is continued into Suabia 

 and Franconia, the principal ridges of the Apen- 

 nines, and multitudes of beds in France and 

 England. It consists of limestone-schists, rich 

 in fishes and Crustacea ; vast beds of oolites, or 

 of a granular limestone ; grey marly limestones, 

 with pyrites, characterised by the presence of am- 

 monites, of oysters with recurvate valves, named 

 Gryphaeae, and of reptiles, which are remarkable 

 on account of their forms and structures. 



Large beds of sand and sandstone, often pre- 

 senting vegetable impressions, support all these 

 Jura deposits, and are themselves supported by a 

 limestone, the innumerable shells and zoophytes 

 contained in which induced Werner to give it 

 the much too general name of Shell-limestone, 

 and which is separated by other beds of sandstone, 

 of the kind denominated variegated sandstone, 

 from a still older limestone, which has been not 

 less improperly called Alpine limestone, because 

 it composes the High Alps of the Tyrol ; but 



