and Geognostical Constitution of Spain. 271 



shoot up from them, and also occasion a great uniformity in the 

 nature of Spain, as it brings the climate of a great part of this 

 country to that of a higher latitude. The whole middle part 

 of Spain from the Ebro to the Sierra Morena, and from the 

 frontiers of Portugal to the high mountain range which forms 

 the Avater-shed between the Atlantic Ocean and the Mediter- 

 ranean Sea, is formed by them into a widely extended table-land, 

 of which tiie different plains, separated from each other by 

 ranges of mountains, arc from 2000 to 2500 feet above the level 

 of the sea ; but, in regard to it, we have to remark, that the table 

 land of Old Castile in general occupies rather a higher level than 

 that of New Castile. The southern part of Spain also possesses 

 single table lands, which, however, have neither the extent nor 

 the connection of those situated in the middle of the penin- 

 sula. 



Geognostical Structure. 

 The principal mountain chains differ not only in their exter- 

 nal aspect, but also in their internal composition : they appear 

 more as different individuals than as members of a single sys- 

 tem. They have this in common with one another, that their 

 nucleus consists, in whole or in part, oi primitive and transition 

 rocks ; but not only the species, but also the relations of these, 

 vary in the different chains. A great body of granite, which 

 seldom reaches the highest points of the country, and contains 

 subordinate beds of gneiss and other primitive rocks, ranges 

 through the Pyrenees properly so called. It is surrounded by 

 a predominating mass of crystalline slate and of transition rocks, 

 among which the most abundant are clay-slate and limestone 

 On the contrary, on the western continuation, in the Biscayan 

 mountains, the older rocks are not widely distributed, and ap- 

 pear first in Gallicia, at the western extremity of the northern 

 mountain chain, where, according to Humboldt, granite accom- 

 panied by crystalline slates appear again, and in great extent. 

 The princii)al mass of the mountain chain which separates Old 

 from New Castile is composed of gneiss and granite. In the 

 chain of mountains extended between the Tagus and the Gua- 

 diana, according to Link, the principal rock is granite. The 

 long ridge of the Sierra Morena contains principally transition 



