THE TEE-ADAMITE EARTH. 



205. We shall now briefly explain the stratigraphical charac- 

 ters by which these several dates have been ascertained. 



I. SYSTEM or VENDEE. In the earlier researches of M. Elie 

 de Beaumont, the Hundsruck system, the elevation of which 

 appeared to precede immediately the Silurian period, was assumed 

 to be the earliest catastrophe of that kind of which the crust of 

 the earth afforded any ^evidence. Observations more multiplied 

 and exact, and a more elaborate discussion of the phenomena, 

 discovered by his own labours and those of other geologists, have, 

 however, conducted him to the conclusion that four of the exist- 

 ing mountain systems were produced at much earlier epochs. 

 The first of these, to which the French province of La Vendee 



has given its name, is repre- 

 sented with the Cumbrian 



Cambrian j> i? Sea. beds horizontal at its base, in 



the section fig. 118, where 

 a represents the mountain 

 range, and b the Cumbrian 

 deposit. 



We may therefore imagine b to be the sea of the epoch, which 

 succeeded this elevation, in the bottom of which the Cumbrian 

 formation was deposited. It is in this sense that the Cumbrian 

 sea is to be understood, and a like form of expression will be 

 used in a corresponding sense in other cases. 



The date of the catastrophe by which the Vendee system was 

 pushed up, must therefore be prior to the deposition of the 

 Cumbrian strata. 



This mountain system has hitherto been but little studied. 

 Traces of it are shown by M. de Beaumont to exist in schists of 

 Belle-Isle, of the embouchure of the river Villeine, in the mica- 

 schists or gneiss on the banks of the river Blavet (dep. Morbihan), 

 in Beaupreau, and Bourbon- Vendee. 



206. II. SYSTEM OF FINISTERE. By the catastrophe which 



produced this system, the 

 Cumbrian formation &, fig. 119, 



Fig. 119. was uplifted, and in the period 



Green-' slate Sea. O f tranquillity which followed, 



the waters deposited the strata 

 of green slate of Longmynd 

 in Wales. These last, c, are 

 accordingly seen in horizontal 

 strata along the base of the system. 



The date of the catastrophe is therefore posterior to the deposi- 

 tion of the Cumbrian formation, and anterior to that of the green 

 slate of Longmynd and Westmoreland. 

 12 



