348 M. F. Le Play on the Geology of [May 



considers that the quartzoze chains have not been elevated, 

 but have been, as it were, sculptured out by the gradual 

 degradation of the surrounding country, the constituents 

 of which are much less durable than the indurated quartz. 



The limestone of Llerena is very rich in metals, and forms 

 the summits of the mountains which run from south-east 

 to north-west, crossing the road from Badajoz to Seville. 

 The silver mines of Guadalcanal are situated in hills of 

 slate and greywacke, at the south-east extremity of this 

 limestone ridge. More southerly, compact and saccharoid 

 limestone is often met with, as at Cazalla and Pedroso. 



The coal formation does not occur to any great extent 

 in Estramadura, but, being distributed in small patches on 

 the surface of the transition formation, throws some light 

 on the geology of the district. Impressions of equiseta and 

 filices exist abundantly in the rocks of the coal basons The 

 valley of Espiel, which is probably united with the coal 

 bason of Valmez, is surrounded by high transition hills. 

 The predominating rock is a quartzoze conglomerate, pass- 

 ing into pudding-stone, and is often impregnated with oxide 

 of iron. 



The inhabitants raise for their own use a little coal, but 

 never dig deeper than nine or ten feet. It is very friable, 

 but possesses all the other qualities of good coal. The coal 

 basin of Fuente del Arco is surrounded by greywacke rocks, 

 and is situated at the foot of the limestone ridge of Llerena. 

 At Alanis, where coal has been dug, in addition to conglo- 

 merates and psammites, an argillaceous rock appears, con- 

 taining felspar and ochre. The bason of Villa Nueva del 

 Rio, on the Guadiana, is the only place where coal can be 

 said to be worked. The surface of the earth consists here 

 of conglomerate or pudding-stone. Below it are found 

 layers of coal and slate-clay, which is black, bituminous, 

 and contains numerous fossil impressions. The coal is of 

 good quality, but has only been extracted from the super- 

 ficial bed, by numerous pits which cover the surface. It 

 is consumed principally by the steam boats, and at the 

 forges of Pedroso. 



4. Tertiary Rocks. — Near Cordova these rocks appear in 

 the form of shell limestone, of a porous structure, contain- 

 ing the remains of many animals, and among others^ a 



