412 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



for statuary purposes, ou account of its preserving almost indefinitely 

 its natural whiteness. We also possess other small detached lacus- 

 trine deposits in the centre of Spain, as e. g. at Libros near Teiiiel, at 

 Calata^nid, where fine specimens of sulphate of magnesia are collected, 

 at Helhn and Benamaurel, already quoted for the production of sul- 

 phur, at ^lohna d'Aragon with its Neritma, nov. sp., and several 

 other localities. 



It is well knoTMi that the surface of Spain is very mountainous and 

 broken up. The only plain of any extent is that of La Mancha in 

 New Castille, from Tembleque to Santa Cruz de Mudela, a distance of 

 twenty leagues, and elevated more than 2000 feet above the level of 

 the sea. All the other lacustrine plams of the tertiary period have 

 been washed out and furrowed by ante-historic torrents, and by the 

 great rivers which traverse them, which have carried off the greatest 

 portion of their mass, and have moreover cut out the rapines which 

 surround the partial and isolated hills, the horizontal summits of 

 which once formed the bottom of the ancient lake. Other plateaux, 

 on the other hand, are, as we have already pointed out, the bottoms 

 of the cretaceous ocean, which, while being upraised to a considerable 

 elevation, have accidentally preserved their original horizontahty. In 

 all the other formations, and even in the cretaceous beds, the strata 

 have generally been tilted m a thousand ways, dipping in ever}" direc- 

 tion, and with eveiy possible degree of inclination, being sometimes 

 quite vertical and even partially reversed. On seeing all these up- 

 heavals, all these dislocations, and all the different characters of 

 mountains which have resulted therefrom, it is at once evident that 

 many instances of eruptive rocks must be looked for. 



In point of fact our soil has never been at rest, nor is it so even at 

 present. The plutonic eruptions which have pierced the gneissoid 

 rocks have been already pointed out in the western districts ; the 

 euphotides, diorites, and black porphyries are more frequent in the 

 central parts of Spain ; and the trachytes are almost exclusively con- 

 fined to the shores of the Mediterranean, and particularly to the 

 southern portion between Marbella and Carthagena. The remarkable 

 and singular deposit of quicksilver of Almaden and xllmadenejos must 

 have been occasioned by the action of the euphotides and other 

 analogous volcanic rocks which have burst forth in this district and 

 moulded the mountains or Sierras in such a singular manner. The 

 veins and other metalliferous deposits of Carthagena, Mazarron, and 

 Sierra Almagrera, which pelded such wealth to the Carthaginians 

 imder Hannibal, and from which we still derive considerable benefit, 

 are certainly contemporaneous with the basalts of Cabo-de-Gata and 

 of Vera, and the trachytes of Mazarron. 



Earthquakes are still often felt at Granada and along the coast of 

 the province of Alicante, where their effects have been very disastrous. 

 Much further in the interior, in the small Sierra del Tremedal or di- 

 strict of Albarracia,in the province of Teruel, eruptions and shocks have 

 been very frequent since the most remote periods ; the black porphyry 

 is there seen traversing the altered strata of the oolitic formation. 

 The old inhabitants of the country speak of sinking of the ground 



