1823.] the principal Mountain Chains of Europe. 141 



pied by the coal measures, and surrounded by zones of carboni- 

 ferous limestone, the whole reposing on one vast tract of old red 

 sandstone. Of these basins, the largest is situated in South 

 Wales, and occupies the greater part of Glamorganshire, extending 

 into Monmouthshire on the east, and Caermarthen and Pem- 

 brokeshire on the west. The next in importance occupies the 

 south of Gloucester, and the north of Somersetshire. It is parti- 

 cularly interesting to the geologist, because the more recent 

 formations sweep over a part of it ; and their relations with the 

 coal series may here be ascertained by actual sections. Coal 

 shafts being sunk even from the lower oolite through the lias and 

 new red sandstone into the coal measures. The third basin in 

 point of extent is intermediate in position between the other two 

 occupying the forest of Dean, between the Severn and the Wye. 

 Trap rocks (principally basalt, greenstone, and amygdaloid], 

 are associated with and overlie many of these districts, especially 

 those of Northumberland, Staffordshire, and Shropshire. 



(E.) France. 



As we have already traced coal fields in the north of Europe, 

 apparently connected with the central system of Scotland, so we 

 might naturally look for the resumption of those of the south- 

 western English counties in the opposite regions of France. It 

 is true, indeed, that in the south of Somerset and through 

 Devonshire, no coal has been observed ; being probably con- 

 cealed by the advance of the overlying deposits of new red sand- 

 stone which are there in close contact with the transition chains. 

 These transition chains cross, as is well known, from Devon to 

 the peninsula of the Cotentin in Brittany ; and we find, as might 

 be expected, a small coal field reposing against their eastern side 

 at Litry on the south-west of Bayeux ; further south, where the 

 Loire enters between the continuation of these chains, between 

 Angers and Nantes, are more extensive deposits of this formation. 



In the centre and south of France, there are some limited coal 

 deposits lying in the valleys of the Loire, the Allier, the Creuse, 

 and the Dordogne, the Aveyron and the Ardeche between 

 ridges proceeding from the primitive central group connected 

 with the Cevennes, and also on the south-east between the 

 Cevennes and the Rhone. 



Several particulars concerning some of these districts may be 

 found in the account of the geological speculations of Mr. Rouelle 

 in the first volume of the Geographie Physique, forming part of 

 the great Encyclopedie Methodique ; the Annales des Mines 

 for 1821 contains some information concerning of those near St. 

 Etienne, department of the Loire, and a full account of those 

 of the Aveyron. 



From the south of France we may proceed to Spain, which 

 could not so conveniently be included in any other part of our 

 .survey. Coal is here mentioned as occurring in eight places in 



