226 



CALCAIRE GROSSIER. 



Feet. Inches, 



7. Stinkstone, a bituminous limestone with ') 



bones and river shells, the roof of > 1 to 2 feet, 

 the coal - - - - y 



8. Coal 



0 



6 



9. Bituminous schist 



0 



6 to 8 



10. Coal 



2 



0 



11. Bituminous clay - - - 



6 



0 



12. Molasse and sandstone 



66 



0 



The bituminous strata, and shaly limestone, possessed 



all the char- 



acters of beds in the regular coal formations in England : probably, 

 the fetid quality of the limestone No. 7, was derived from the abund- 

 ance of animal matter which it might contain. JNo. 2. is subcrystal- 

 line, and, in its mineral characters, bears a near resemblance to moun- 

 tain limestone. 



Above the London clay, there is no calcareous formation, except 

 in the Isle of Wight, but in the Paris basin there are two ; of which 

 the lowest is called Cnlcaire grossier. 



Le calcaire grossier, or coarse limestone of Paris, is deposited 

 upon the plastic clay, as the latter is upon the subjacent chalk : be- 

 tween the plastic clay, however, and the calcaire grossier, there is a 

 bed of sand ; but geologists are not determined, to which of the two 

 formations it belongs. The calcaire grossier differs in its quality in 

 the different beds, but it may be described generally as a yellowish 

 earthy limestone, which bears some resemblance to Portland stone in 

 its fracture, texture, and colour; but it is not oolitic. The strata of 

 limestone alternate with argillaceous marl and shale, and with calcare- 

 ous marl. 



The lowest bed of calcaire grossier is soft, and much intermixed 

 with green particles and sand ; it contains a great number of the fos- 

 sils called nummulites, on account of their being flat and round, and 

 resembling in shape a small coin. Tfie shells in this bed are in high 

 preservation. In the beds immediately above, called the middle 

 beds, there are a prodigious number of marine shells, and also the 

 stems and impressions of leaves of plants that are not marine. In 

 the lowest and middle of the calcaire grossier, no less than six hun- 

 dred different species of shells are found. 



In the upper part of the calcaire grossier, the strata are several 

 feet thick, and yield a hard coarse-grained and durable limestone : 

 it is from these sti-ata that the bebt building-stone is procured. It 

 is often nearly filled with shells of the genus cerithium, and has hence 

 been sometimes called calcaire d ceriies. 



Between the strata of building-stone, there often occur thin strata 

 of flint or chert ; in some parts these siliceous strata enlarge into 

 thick beds of chert, {silex come,) or into beds of sandstone contain- 

 ing marine shells; in the beds of this sandstone, at Pierrelaie, fresh- 

 water shells have been discovered, mixed with numerous marine 



