346 M. F. Le Play on the Geology of [May 



of diallage, which possesses generally a green or greenish- 

 brown colour. They are very hard, and are not easily 

 decomposed. Near Almaden, in the bottom of a valley, a 

 great quantity of blocks of euphotide exist, which are 

 employed for fencing in the road to Madrid. It is com- 

 pact, and admits of a fine polish, the diallage frequently 

 approaching the appearance of actinote. It deserves to be 

 noticed that in the cinnabar veins of Almaden, large por- 

 tions of a rock analogous to euphotide are met with. At 

 Guarena, and upon the banks of the Guadiana, near Merida, 

 euphotide occurs in the tertiary beds. On the right bank 

 of the Guadiana, near Badajoz, the same rock is met with, 

 associated with dolomite and travertine, or porous lime- 

 stone, containing fresh water fossils. Sometimes the dial- 

 lage is distinct in the felspar basis ; it often contains actinote 

 passing into asbestus, pyrites, quartz, green talcose mica, 

 and chlorite in small scales. To the south-west of Albu- 

 querque, there are, fragments of euphotide similar to those 

 of Almaden, and considerable quantities are found on the 

 greywacke, which extends as far as Portugal to the west of 

 this city, in which country it very probably occurs in situ. 



Near Cazalla, in the Sierra Morena, large blocks of 

 euphotide are strewed about, consisting of greenish felspar, 

 and of olive-green diallage, interspersed with small frag- 

 ments of protoxide of iron, which are sometimes so abun- 

 dant as to form the principal portion of the rock. At 

 Pedroso, Fuente del Arco, and Higueira, rocks possessing 

 a granitic structure, consisting of felspar and quartz, occur. 

 They appear to be of the same nature as euphotide. Asso- 

 ciated with the euphotide of Almaden, there are trap blocks 

 on the tops of the hills, having often the aspect of basalt, 

 and are obviously euphotide or diorite, cooled under diffe- 

 rent circumstances. 



2. Mica Slate shewing itself near Albuquerque, in contact 

 with granite, is composed of a clay-slate basis, impregnated 

 with mica or talc, and gradually passes into clay-slate. 

 Near Cordova it also occurs in the midst of transition rocks, 

 and in contact with granite at Pedroso, where the quartz 

 predominates, and gives the rock the appearance of gneiss. 



3. Secondary Rocks. — These correspond with those of the 

 rest of Europe, and afford a strong presumption of the 



