1850.] EZaUERRA ON THE GEOLOGY OF SPAIN. 409 



richness and the quantity of the ore, is most promising. The non- 

 argentiferous galena is generally more regular, and a few productive 

 veins of sulphate and oxide of antimony also occur, as, e. g. in the 

 neighbourhood of Ateca, in the province of Zaragoza. 



In several places the rocks of the oolitic group have been affected 

 by volcanic eruption, by which they have been altered, their colour 

 and structure changed, and all trace of fossil remains obliterated, so 

 that it becomes difficult even for a practised geologist to classify them 

 properly. Thus it is not extraordinary that travellers en chaise de 

 poste have fancied that they saw in the centre of Spain variegated 

 marls and red sandstones, trusting only to the external aspect of the 

 rocks seen from the road. I am satisfied that further and more de- 

 tailed observations will show that the oolitic and liassic formations 

 are more extensively developed than has hitherto been supposed, i. e. 

 that they will be discovered over a great portion of the South of the 

 Peninsula. 



Other phaenomena, which farther observations may perhaps tend 

 to generalize, are the thermal springs which rise up in the Jurassic 

 formations at or near the point of junction with the more recent for- 

 mations. We may mention, by way of example, the hot springs of 

 Fitero in the province of Navarra, Arnadillo in the province of 

 Logrono, and Alama near Calatayud. There are also cold sulphu- 

 reous springs like those of Paracuellos in Aragon, and those of Gra- 

 valos in Castille. It must, however, be observed that these same 

 phsenomena also occur in the cretaceous formations, although not so 

 frequently ; amongst these latter are the *' Caldas de Catalogna," 

 and the " Caldas des Asturias," with the geological conditions of 

 which I am not quite acquainted, but I believe them to belong to the 

 cretaceous beds. It is probable that similar cold sulphureous springs 

 existed during the tertiary (pliocene) period ; at least it is only by 

 such a supposition that we can explain the origin of the vast deposits 

 of sulphur which are worked at Hellin and Benamaurel in the pro- 

 vince of Albacete, and of that of Libros in the province of Teruel, the 

 argillaceous beds of which are studded with Flanorbis and Limnceus 

 internally filled with native sulphur. 



The Cretaceous formation covers the whole southern slope of the 

 great chain of the Pyrenees, extending westwards into the Basque 

 country, to the mountains of Santander, and part of the Asturias. 

 To speak more correctly, this cretaceous zone of the shore of the 

 Cantabrian sea is rather a continuation of that which comes from 

 France along the northern slope of the Pyrenees. The cretaceous 

 zone of the southern slope also extends towards the west through 

 Navarre, a portion of the Basque pro\dnces, the province of Burgos, 

 and the mountains of Leon, so that the great cretaceous deposit of the 

 south of France and the north of Spain is divided in two by the 

 transition and plutonic rocks of the Pyrenees, the Jurassic rocks of 

 Biscay, and the Devonian rocks of the Cantabrian mountain-chain. 

 From Figueras in Catalogna to Oviedo in the Asturias is a distance 

 of more than seven geographical degrees. 



The Spanish cretaceous zone stretches towards the south with very 



