112 



TERTIARY FORMATION. 



deposite belongs to the eocene formation of Mr. 

 Lyell ; and scarcely any of the fossils contained in 

 it can be identified with existing species. 



The middle tertiary constitutes the miocene forma- 

 tion of Mr. Lyell ; and comprehends the lower 

 fresh- water, the upper marine, and the upper fresh- 

 water of the vicinity of Paris. The lower fresh- 

 water contains siiicious limestone, with gypsum, 

 and the bones of extinct animals and fresh-water 

 marls. The upper marine consists of gypsum marls, 

 sands, and sandstones, and marine marls and lime- 

 stone. The upper fresh-ivater contains millstone* 

 without shells, and fresh-water marls. The depos- 

 ites of this formation contain an increased number 

 of recent shells. Indeed, all its shells are analogous 

 to those of fresh water. Being composed of a mix- 

 ture of calcareous and siiicious earths, sometimes 

 intermixed and at other times separated, when the 

 calcareous portion predominates it forms a lime- 

 stone. This limestone has often a fine grain, and 

 splintery, conchoidal fracture, resembling the tran- 

 sition marble, and receives a fine polish. Some of 

 the jets d'eau in the galleries of the Tuilleries are 

 made of this marble. Many of the harder fresh- 

 water limestones rapidly disintegrate when ex- 

 posed to air and moisture, and, falling to the state 

 of marl, are used as a manure. 



The upper tertiary, or the pliocene of Lyell, 

 includes what is called the crag in England, which 

 is made up of sand and gravel, chiefly in the coun- 

 ties of Norfolk and Suffolk, the tertiary hills of Si- 

 cily, and the sub-Apennine marls. The crag chiefly 

 rests on chalk or London clay. It would seem to 

 have been an ancient beach, where sand, gravel, 

 earth, and red ferruginous sands, containing vast 

 quantities of fossil shells, succeed each other. The 



* From this formation the French buhr millstones are ob- 

 tained. It has a cellular appearance, being full of cavities. 



