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



generally been taken advantage of by invaders, for military 

 stations. 



Estramadura, therefore, may be described as an elevated 

 plain, 550 metres (1804 feet) above the level of the sea, and 

 500 (1640 feet) above the plain which borders the Guadal- 

 quiver, through which the Guadiana runs, at an equal dis- 

 tance from the Guadalquiver and Tagus, in a direction a 

 little to the south of west, while the Sierra Morena, which 

 traverses the south of the district, triples, in many places, 

 the difference between the banks of the Guadalquiver, and 

 the numerous partly isolated chains afford variety to a 

 country which is always of a rude character. The different 

 formations met with in this district may be considered in 

 the following order, beginning with the most ancient 

 rock : — 



1. Granite constitutes a very considerable portion of 

 Estramadura. Between Garlitos and Almaden, an isolated 

 tract of this formation occurs, extending from north-east 

 to south-west- The rock is composed of white felspar, 

 reddish-brown mica, and small portions of quartz, in minute 

 quantities, and possesses often a foliated structure. The 

 most important mass of granite, to the south of the Gua- 

 diana, is that which lies on the north border of the Sierra 

 Morena, extends from the east of Puerto Blanco to the 

 west of Benalcezar, and is surrounded by hills of schist. 

 The soil is derived from the disintegration of the granite. 

 To the north-west of this basin, a considerable extent of 

 granite is met with, the limits of which are marked by 

 Castuera, Campanario, Quintana, Zalamea, Malpartida, 

 and Bengareucea. On its eastern boundary the formation 

 is covered with granitic sand, and the rock possesses an 

 olive-green colour, derived from the mica. 



In the middle of the formation, near the ancient mine of 

 El-Chantre, which has been long abandoned, the felspar 

 has, in decomposing, assumed a grayish appearance, and 

 the rock is covered with rusty stains, produced by the action 

 of the weather upon the mica. About Quintana the granite 

 consists of small grains, the hyaline quartz and felspar 

 forming a beautiful white basis, through which mica is 

 plentifully distributed. Here also occur large tabular 

 masses of granite, sometimes 100 feet in diameter, which 

 have become polished by the atmospheric influences. At 



