260 Scientific Intelligence. 
traversed by veins or dykes of porphyritic granite. Only at the northern 
extremity, viz. between Aracéna and Lleréna, in the villages of Zufre | 
and Santa Olalla, is a great syenitic outburst visible. 
The most important of these granitic ramifications to the east, is that 
which passes by the Sierra de Gridos, Sierra d’Avila, and the Guadar- ’ 
rama, to Somo Sierra, in a direction from southwest to northeast. The 
great granitic outburst of Truxillo and of the mountains of Toledo 
does not extend so far to the east. A third, which is not so well mark- 
as the other two, 7. ¢. does not appear on the surface with the same . 
oo is that which has probably given its present form to the a 
pr 
ierra Morena. It terminates at Linares, in the province of Jaen 
deposits. There are some however of considerable importance. All 
the copper deposits of the district of Rio Tinto occur in talcose schist, 
in the vicinity of the granite. The famous mines of Guadalcanal 
Ca i 
covered at Hiendelencina, in the province of Guadalaxara, traverse 
the real gneiss, and are also not very distant from the granite of Somo 
Sierra. 
The plutonic rocks themselves are still less rich in useful metals 
compared with their great development. he most important deposit 
ation must also be referred the carbonate of lead and the antimo- 
nial-ochre of Losacio, in gneiss entirely surrounded by granite. Th 
nd abundant minerals of Losa ve not yet proved profitable 
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, aré 
hot worth mentioning; they are very poor, and are not derived from 
the same source. 
stone, or rather metalliferous limestone. Fossils are very sca 
The Silurian formation is well characterized in the Sierra Morena, from 
Santa Cruz de Mudela to Almaden, with its remarkable deposit of Cin- 
