54 Instihde of France. 



if a shell is a salt- or a fresh-water one ; but they do not weaken 

 the fact of there beii\i^ immense beds where there are only shells 

 well known to be of fresh -water origin; and thev even account 

 for our also finding these shells dispersed in beds of marine 

 formation. 



M. de Scrres places the lignites or bituminized woods among 

 the fossils which are nnwt frequently mixed with terrestrial and 

 fresh- water shells ; and this renders it probable that these woods 

 have grown on the spot where they are now found, besides 

 agreeing with all the other facts, which show that the surface of 

 the present globe was dry, and peopled with animals and ter- 

 restrial vegetables, previous to the last irruption of the seas. 



Two young and expert naturalists, Messrs. Desmarets and 

 Leman, have found ia the fresh-water strata of our neighbour- 

 hood, even shells of those small eiiinmostractcB which are called 

 cypris, and even the seeds of the plant known by the name of 

 chara. These seeds had been taken for shells, and the name 

 oi oyrngoni'es was given them. 



The geological system of the environs of Paris, which formed 

 the chief object of the observations and discoveries of Messrs. 

 Brongniart and Cuvier, is now followed up with great zeal by 

 several learned naturalists. Messrs, de Tristan and Bigot de 

 Morogue have carefully described the districts adjoining the 

 Loire; and M. Omalius de Halloy, mining engineer, in following 

 up these inquiries, and those of our associate M. Desmarets, 

 is occupied in laying down all tlie boundaries on a chart. The 

 beds of this system deposited upon chalk rc])resent an irregular 

 and curvilinear trapezium, of which the southern side parallel 

 to the Loire runs along this river on the south from Cosme 

 to below Blois ; the eastern side passes near the towns of Mon- 

 targis, Nemours, Montereau, Villenoxe, Sezanne, Epernay, 

 Laon, Crepy, and La Fere ; the northern side near the towns of 

 Chaunv, Noyon, Coiupiegne, Clermont, Beamnont, Chaumont, 

 and Gisors ; lastly, the western side descends by Mantes, Hou- 

 dan, Epernon, Auneau, and along the Loire to the vicinity of 

 Vendome, fnnn which it rejoins the Loire at Blois. All this 

 space is surrounded with chalk ; and the chalk, in which M. de 

 Hallov has recognised three very distinct modifications, is sur- 

 rounded itself, except towards the sea, with a compact cal- 

 careous substance usore ancici:t, which forms a great part of 

 Berry, Burgundy, and Lorraine, extending to Vosges, and which 

 reappears beyond the Black Forest in Franconia and Hesse. 

 The formations of ; lie system of Paris send out various ramifi- 

 cations over this chalk, while the agriculture, industry and re- 

 sources of a district are frequently detailed by the geology of its 



soil. 



