1835.] Estramadur a and the North of Andalusia. 345 



Zalamea, a species of black porphyry appears, consisting of 

 a basis of amphibole and felspar, through which felspar 

 is disseminated ; M. Le Play calls it Melaphyre. Although 

 granite appears so frequently among the transition rocks 

 on the table land of Estramadura, it is seldom met with 

 among the rocks of the same formation in the Sierra 

 Morena, afid when it does occur among these mountains, 

 it is generally in a deep bed of a rivulet, as at Villaharta, 

 in the channel of the Rio Cuzna. Here the greywacke and 

 schist appear to be impregnated with the debris of the 

 granite. On the south of Pedroso, granite, to a small 

 extent, occurs, which, in decomposing, has given origin to 

 a thick layer of sand overlying it. 



On the north of the Guadiana, the rock appears at 

 Albuquerque, containing very large felspar crystals, which, 

 in decomposing, become gray, and give the rock an appear- 

 ance like trachyte. The quartz is reddish. The town pre- 

 sents a remarkable appearance, in consequence of the houses 

 being built among immense masses of rock, which has pro- 

 duced the most tortuous streets imaginable. At Malpartide 

 another tract appears, where, from the nature of the soil, 

 large reservoirs of water have been formed for washing the 

 wool, which forms the staple product of the industry of this 

 country. The hills in this neighbourhood are covered with 

 rounded blocks of granite, lying over the granite soil, and 

 appearing to have no connexion with the subjacent rocks. 

 Hence, the inhabitants consider these the work of human 

 industry. M. Le Play explains their origin very satisfac- 

 torily, by considering these masses to have been connected 

 by narrow necks to the subjacent rocks, and that this bond 

 of union gradually decomposed, and left the main portion 

 of the blocks above the disintegrated matter. The Sierra 

 de Montaches, consists of granite, but the effect of external 

 causes in decomposing it are not nearly so apparent as at 

 Malpartida. A long band of granite extends from the 

 Tagus, by Truxillo, south easterly to Torjta, at no great 

 distance from the Guadiana. Detached blocks are observed 

 distributed as at Malpartida, upon the hills, the origin of 

 which admits of a similar explanation. 



Euphotide and diorlte. — These consist of compact felspar, 

 containing a great quantity of crystals, or lamellar pieces 



