22 M. D'Omalius D'Halloy on 



La Beauce, or the great platform of freshwater limestone 

 between the Seine and the Loire, is remarkable for its uni- 

 formity and the almost exclusive culture of corn. 



The sandy deposit covering the freshwater limestone, 

 forms a particular region on the SE. of la Beauce, corres- 

 ponding to the country commonly named Gatinais, which is 

 low, wet, unproductive, and generally covered by forests. 



This same sandy deposit, mixed with the mud of the 

 Loire, gives rise, along that river from Orleans to Blois, to a 

 vineyard so considerable, that it may be regarded as a small 

 physical region, separating la Beauce from La Sologne. 



What has been said on the physical and geographical ex- 

 tent of the portion of the basin on the south of the Seine, is 

 sufficient to make known that of the limits of these countries; 

 I shall confine myself therefore to a rapid sketch. 



It has been seen in the work of Messrs. Cuvier and Brong- 

 niart, that these limits are clearly defined between Mantes 

 and Epernon ; as also to beyond Gue-de-Longroi, on the 

 east of Chartres, where the right bank of the Voise forms a 

 well determined inclination, forming the edges of the Pari- 

 sian rocks, opposite the chalk plain of the environs of 

 Chartres. This plain is, like those on the north of the Seine, 

 low and even, rising towards the hills of le Perche. 



These limits afterwards take a SW. direction, passing 

 near Bonneval, and follow the banks of the Loire, at a cer- 

 tain distance, as far as opposite Vendome, whence they bend 

 towards Blois. There is here no physical demarcation ; the 

 surface of the Parisian formation is almost on the same level 

 with the chalk plain, arising from the inferior formalions 

 having ceased, as has been above stated. 



It afterwards becomes extremely difficult to assign the 

 true limits of the Parisian rocks on the south of the Loire, 

 because they lose themselves under the sandy deposit of 

 intermediate origin, which I have noticed above. Never- 

 theless some outcrops and quarries expose freshwater lime- 

 stone .along the left bank of the Loire, from Blois to Cosne; 

 but with this difference, that the chalk which was hid in 

 the northern part of the Sologne by sand, reappears beyond 



