192 SILURIAN AND DEVONIAN EPOCHS. 



of the globe, so often disturbed, must have presented great varia- 

 tions in the relative extent of land and sea, and successively passed 

 through many different shapes, to reach its present state. But, 

 even in Europe, the only part of the world in relation to which 

 positive information has been obtained, it is very difficult to say 

 what may have been its condition in the most ancient epochs. 

 The reason of this is, that having for a long time confounded, under 

 the name of transition formation, deposits of very different epochs, 

 we are not now able to distinguish, with sufficient clearness 

 throughout, the limits of different formations comprised in it. Nor 

 do we know, and this is a great obstacle to tracing the continents 

 of the ancient world, what parts were successively sunk at each 

 catastrophe, and the extent of which we can only know from induc- 

 tion. It was not until after the appearance of the jura'ssic forma- 

 tion, the limits of which are clearly marked, that we are able to 

 distinguish, with precision, the shape and extent of lands in the 

 midst of seas in which these deposits were formed. 



By the term epoch of 1 his or thai formation, we understand the 

 period of time during which the formation was produced beneath 

 the sea, around the upheaved deposits of the preceding epoch. 

 For example, the jura'ssic epoch indicates the time during which 

 the deposits of the Jura were formed in the seas where the 

 upheaved deposits of the trias and all that preceded were traced. 

 The term, sea of such an epoch, as jura'ssic sea, creta'ceous sea, 

 &c., is often used in the same sense. 



Silurian and Devonian epoch. At the time when the Silurian 

 and Devonian systems were formed in the midst of seas, it is evi- 

 dent there were different portions of land in Europe uncovered, 

 which resulted as much from the upheaval of the Hundsruck as 

 from previous catastrophes : we have seen those of considerable 

 extent which entirely escaped these deposits, and which, in conse- 

 quence, must have been raised above the waters in which they were 

 formed. In France, there was at least one island, of the Cambrian 

 formation, near the gulf of St. Malo, on a part of Brittany and of Nor- 

 mandy; the great granitic plateau, which comprises Limousin, Au- 

 vergne, &c., where the upheaval of the Hundsruck was manifest by 

 the direction of certain uptilted beds of gneiss, arid by the anfractuosi- 

 ties in which the coal formation was subsequently deposited, must 

 have been, at that time, above water, and, perhaps joined, at the 

 south, to the ancient group which preceded the Pyrenees. The 

 mountains of iMaures also existed, and, perhaps, a part of the 

 formations comprised between Toulon and Inspruck, in a south- 

 west and north-east direction. Some parts of the centre of Vosges, 

 and of the Black Forest, Eiffel, the Hundsruck, where the first 

 upheaval is clearly indicated, and Ardennes, were necessarily 

 above water, as well as the county of Nassau, the Hartz, all the 

 centre of Germany, including Saxony, Bohemia, and Moravia. 

 TV same is true of Scandinavia, and a part of the British islands. 



