cf the Bnvirons of Paris* 2$, 



from ihc continent by the valley of Bievre and that of tho 



hills of Jouy. 



But afterwards, from St. Cyr to Orleans, there is no 

 longer ciuy complete interruption, although the rivers Bievre, 

 Ivette, Orge, Etampcs, Essonne, and Loing, cut deeply 

 into the continent on the east coast, while the rivers of 

 Vesgre, Voise, and Eure, do the same towards the west. 



'I'he most rugged and uneven part of the surface, and 

 that which would furnish most islands, would be what h 

 vulgarly called the GatinoU Frangois^ and particularly that 

 part in which the forest of Fontaincbleau is situated. 



The slopes of this immense platform are generally very 

 abrupt ; and all the ravines which we find in them, as well 

 as those of the valleys, and the wells dug in the high parts, 

 show that its physical nature is the same every where, 

 being formed of one prodigious mass of fine sand which 

 covers the whole surface, passing equally over all the other 

 soils or inferior platforms which this great plain overlooks. 



The edge of this platform towards the Seine, from th« 

 Maulde to Nemours, will therefore form the natural limit 

 qf the basin which we are about to examine. 



From below its two extremities, ?*. e. towards theMaulde 

 and a little beyond Nemours, immediately issue two 

 portions of a platform of chalk, which extends in every 

 direction and to a great distance, in order to form the wholt? 

 of Haute Normandie, Picardy, and Champagne. 



The interior edges of this great girdle, which pass from 

 the east by Montereau, Sezaime, and Epernay ; from the 

 west by Montfort, Mantes, Gisors, and Chaumont, in order 

 to approach Compiegne, and which form at the north-east 

 a considerable re-entering angle which embraces the whole 

 of the Laonnois, complete, together with the sandy coas^ 

 now described, the natural liniit of our basin. 



But there is tliis great difference, that the sandy platform 

 which comes from Beauee is higher than the others, and 

 is consequently the most modern, and finishes completely 

 the stretch of coast which we have marked ; while, on the 

 contrary, the platform of chalk is naturally more ancient 

 and lower than the rest, only ceasing to appear outside of 

 tlie girdie above mentioned ; but so far from being at an 

 end, it visibly sinks under all the other strata : we find it in 

 short wherever we dig sufficiently deep under the latter, 

 and it ev^en rises up in some places, piercing as it were 

 through the other strata. 



We may therefore conclude that the materials which 

 •ompose the basin of Paris, in the directions to which our 



C 4 incjuiric* 



