1850.] EZQUERRA ON THE GEOLOGY OF SPAIN. 407 



To this last formation must also be referred the carbonate of lead 

 and the antimonial-oehre of Losaeio, in gneiss entirely surrounded by 

 granite. These rich and abundant minerals of Losaeio have not yet 

 proved profitable to the speculators, for want of an economical method 

 of carrying on their operations. The auriferous sands of Galicia, 

 which the Romans worked on so large a scale, and from which the 

 inhabitants still obtain a considerable revenue by washing, and those 

 of the Guadiana and of the Tagus, which are slightly worked in 

 Estremadura, are all derived from the disintegration of the granitic 

 rocks. The auriferous sands of the Darro and the Gerril, sung by 

 the Arab and Andalusian poets, are not worth mentioning ; they are 

 very poor, and are not derived from the same source. 



The oldest sedimentary or transition rocks, in their diiferent stages, 

 the present forms of which are owing to volcanic eruptions, are in 

 Spain most rich in mineral wealth. The whole range of the Cordil- 

 leras of the province of Granada down to the sea, and almost the 

 whole coast from near Gibraltar to beyond Carthagena, belong to 

 this period ; consisting of slates, argillaceous schists, and mountain 

 limestone, or rather metalliferous limestone. Fossils are very scarce. 

 The Silurian formation is well characterized in the Sierra Morena, 

 from Santa Cruz de Mudela to Almaden, with its remarkable deposit 

 of Cinnabar. It also occurs in the mountain-chain of Asturia, which 

 contains coal of good quality. 



The secondary formations, which are shut in between the older 

 rocks and the sea, occupy a great extent in the centre of Spain, ex- 

 tending to the north and to the eastern coast. The greater part of 

 these secondary rocks belong to the Oolitic and Cretaceous periods ; 

 all the members of the series are fully developed except the Muschel- 

 kalk. 



The Devonian formation is very limited. Some traces of it occur 

 in the centre of the Asturias, and a still larger development occurs in 

 the northern part of the province of Le'on, which extends as far as 

 Galicia, following a line parallel with the mountain-chain of Cantab ria. 

 In both these localities the Devonian rocks abound with coal of an 

 excellent quality. That of the Asturias, which was already known at 

 the close of the last century, not only in the Devonian, but in other 

 formations, will hardly stand in competition with other coals, unless 

 the company by which it is worked agree to lay out larger sums in 

 working it. That of Leon is more easily obtained, and although it 

 has only been known for a few years, it is already the source of con- 

 siderable industry in Castille. It is taken to Madrid for the cast- 

 iron foundries and other works, as gas-lighting, &c. 



On the Silurian rocks of the Sierra Morena, which we have alluded 

 to, proceeding towards the south, reposes the great coal formation of 

 Espiel and Belsuez, which may be called the basin of the Guadiato, 

 the river by which it is traversed. This formation may be traced for 

 a distance of fourteen leagues from west to east, and extends to within 

 three leagues of Cordova. At Villanueva del Rio, on the right bank 

 of the Guadalquivir, eleven leagues north-east from Seville, is a small 

 basin of coal, extending over nearly a square league of ground. This 



