the Environs of Paris. 21 



That part of this formation which borders the Loire, and 

 in general all that to the south of Montargis, Neuville, &c. 

 is coyered by a sandy deposit, which might to a certain 

 degree be considered as a fifth and last series, confounding 

 itself with the sands covering the northern part of the 

 Sologne. This sand is generally composed of tolerably sized 

 grains of crystalline quartz, and is accompanied by rounded 

 fragments of the same ; rounded pebbles of white flint , 

 (silex) occur on the surface, at least in the neighbourhood of 

 the Loire. I shall return to the consideration of this sandy 

 deposit, whose geological epoch I shall however not ven- 

 ture to determine ; contenting myself by making known 

 the different opinions that may be entertained on this subject, 

 when I shall in the sequel have exposed some facts, which 

 may serve to develope these ideas. 



It will be seen, from the above, that the principal forma- 

 tions of the Paris basin, notwithstanding their successive 

 superposition, have a real geographical disposition, dividing 

 the country to a certain degree into physical regions, dis- 

 tinguishable by their aspect, and agricultural productions. 



It may have been remarked in the first place, that the 

 calcaire a cerites forms the greater part of the basin on the 

 north of the Marne and the Seine, and a great band on the 

 south of that river, between Versailles and Houdan. If this 

 country is considered in a physical and agricultural respect, 

 it will be observed that it has an unequal surface, furrowed 

 by numerous valleys, of a dry nature, in which the cultiva- 

 tion is much varied, and remarkable for the produce of ^ 

 considerable quantity of wine. 



The country between the Marne and the Seine, commonly 

 known by the name of Brie, is on the contrary wet and 

 covered with marshes, owing to the clay accompanying the 

 siliceous limestone, and the millstone, by which the surface 

 is almost every where covered. 



The sandy formation of the second marine epoch, has not, 

 ^s a principal formation, sufficient geographical extent, to 

 constitute a physical region ; but all the platforms wherp i^ 

 pccursj are covered by large forests. 



