of Serpentine, SfC. in the Apennines. 185 



gists, iSj on the contrary, one of the last rocks of that forma- 

 tion, if even it belongs to it, i. e. if it were wished abso- 

 lutely to comprehend in the transition series the calcareous 

 sandstone of the Apennines and the Alpine limestone, which 

 is, as I shall endeavour to prove, of the same epoch as that 

 of the Apennines, and perhaps even more ancient. 



Article III. 



Determination of the epoch to which the Sandj/ Lime-^ 

 stone immediately beneath the Serpentines belongs. 



It is not sufficient to have recognised, as clearly as may 

 be desired, the order of the superposition of the rocks I 

 have above described ; it must now be determined, if possi- 

 ble, to which epoch of formation, i. e. to which of the great 

 divisions of rocks comprising the crust of the globe, these 

 should be referred, with which we are at present engaged, 

 or at least the lowest of them, for they nearly determine the 

 age of the others. 



Geologists have generally admitted the three great divi- 

 sions which are not volcanic, established by Werner and his 

 numerous disciples : the primitive rocks ; the transition 

 rocks ; and the secondary or rocks of sediment ; but the 

 latter, lately studied with more care, have shewn the neces- 

 sity of a subdivision, and I consider myself to have been one 

 of the first to establish it under the names of inferior, middle, 

 and superior sediment rocks, giving each of these groups as 

 precise limits as the state of science would permit. 



I shall neither recall here the motives of these divisions,, 

 nor the characters of the formations they contain : these are 

 known circumstances, developed in geological works, the 

 details of which would too much lengthen this memoir. I 

 shall content myself by calling to recollection, as a circum- 

 stance less known, and what is not perhaps admitted by all 



