ff ihe Emnroiis of Paris, ^9 



,f«il, in the numerous hillocks oF gypsum which we have 

 examined. The gypsous formation is frequently terminated 

 by a mass, more or less thick, of argillaceous sand, which 

 <:oniains no shells. 



Such are the strata which generally compose the gypsous 

 formation- We were at first led to div'ule it into two, and to 

 separate the history of the marine marles of the top from 

 those of the gypsum, and of the fresh-water marles at the 

 bottom; hut the strata arc so similar to each other, and 

 accompany each other so constantly, that we have thought 

 it right merely to point out this division without making it 

 in reality. 



It now remains to sav a f^w w<^rds, as to the principal 

 <Vifferences presented hy the hillocks which helong to this 

 formation. The gypsous hillocks' form a kind of long and 

 broad zone dire ctcil from the south-east to the north-east, 

 over ahreadth of al'out six leagues (16} miles). It seems that 

 m this zone it is only the enjinences of the centre which 

 present distinctly the three masses of gypsum. Those of the 

 edges, such as the plaster quarries of Clamart, Bogneux^ 

 -Antoni, Mont Valerian, Grisy, &c., and ihoisc of the 

 extremities, such as the plaster quarries of Chelles and 

 Triel, possess only a single mass. This mass seems to us 

 to be analogous to that which the NAorkmen call the first, 

 i. e, the most superficial, since we find in it the fossils of 

 the mammiferae which characterize it ; and since we do not 

 find, in its marles, those coarse and numerous crystals of 

 lenticular gypsum which we observe in the marks of th^ 

 second and of the third mass. 



Sometiniesthe marles above, are almost entirely wanting; 

 sometimes the gypsum itself is totally wanting, or reduced 

 to a thin bed. in the first case the formation is repre* 

 sentcd by the green marles, accompanied with strontian. 

 The gypsous formations of the park of Versailles near Saint 

 Cyr, those of Viroflay, are in the former state, and those 

 of Meudon and Ville d*Avray are in the latter. 



We ought to mention here what has been said in 

 another work *, namely, that the gypsous soil of the en- 

 virons of Paris cannot be referred with accuracy to any of 

 the fv)rmations described by M. Werner or his followers. 

 We have on the above occasion assigned our reasons^ which 

 it is needless to repeat. 



* Brognlart, Mini-ralogie, torn. i. p. 177. 



D 3 Art, 



