VEINS IN GRANITIC ROCK. 565 
found near Quillota, though it is less perfectly crystallized, and the 
albite is not of so clear a white colour. Like many granites and 
syenites, it contains many ovoidal spots of a darker colour than the 
rock, which appear at a distance like imbedded stones; they have, 
however, the same constitution as the rock, except that they include 
more hornblende, and both the hornblende and albite are in finer 
grains. Boulders of the same rock were abundant in the Jaguel 
Valley, one of the gorges of the Andes, and they were often of large 
size; yet no similar rock was observed in place in the hills adjoining 
the valley for the short distance—fifteen miles—which we ascended 
it. ‘This albitic rock appears to be allied to the Andeszte described by 
Mr. Darwin as intersecting the sedimentary rocks of the western 
chain of the Cordilleras, and therefore of comparatively modern 
origin. No facts were observed in connexion with the particular 
ridge here described, which indicated its age. 
From the facts which have been detailed, it appears that the transi- 
tions in the granite to syenite, and to micaceous and hornblendic 
schist, are numerous and interesting. We have found pseudo-dikes 
of argillaceous schist in granite, and not far off, where the granite 
changes to a syenite, there were similar pseudo-dikes of hornblendic 
schist, conformable in position to the argillaceous, and these were 
conformable to lines of fracture near by in a granite cliff free from the 
pseudo-dikes: and we have found these pseudo-dikes increasing in 
extent, and becoming layers of schist. 
A coarse concentric structure often characterizes the granite. On 
the road to the north of Valparaiso, along the coast, there are sections 
in which globular concretions are exhibited to view that are two to 
three feet in diameter. They readily peel off in concentric layers. 
Veins and Dikes in the Granitic Rocks. 
The granite and syenite of this region are remarkable for the num- 
ber and complication of the granitic and epidotic veins. Epidote is 
occasionally disseminated through the rock, but usually occurs in 
narrow seams composing independent veins, or forming the walls of 
the granitic veins. 
Epidotic Veins.—The veins of epidote are usually very narrow, 
seldom exceeding a fourth of an inch, and in general not over an 
142 
