570 CHILE 
The small interior veins, in the cases here explained, often appear 
like distinct veins running through gneiss or mica slate, as is seen in 
the figures. 
One remarkable vein in the same region, has a longitudinal struc- 
ture, and consists of eleven stripes of alternating quartz 
and gneissoid granite, although but a foot wide. (Figure 9.) 
It occurs in a dark-coloured granite approaching gneiss ; 
and as the coating either side is rather soft and epidotic, 
its removal has caused the vein to stand out quite distinct 
from the inclosing rock. ‘The alternations are as follows: 
—1, quartz, forming the centre ;—2, a stripe of gneissoid 
eranite on either side of the quartz ;—3, another layer of 
quartz on each side ;—4, a repetition of the gneissoid granite ;—5, 
narrow stripes of gneiss;—6, external stripes of quartz, containing 
some epidote disseminated or in seams. ‘The third of these stripes is 
less distinct on one side of the centre than on the other. Although 
the several component portions of this riband vein are distinct in their 
characters, yet there are no traces of a line of fissure separating the 
stripes; on the contrary they form a single solid crystalline mass, 
which would break as soon across the quartz as along the line sepa- 
rating it from the gneiss on either side. ‘There are other examples 
of this structure in the same region, but none was observed with so 
numerous alternations. 
Direction and Dip.—Allowing equal importance to all the veins, 
small as well as large, we could deduce from their direction only the 
fact that there is no prevailing course. But from the larger veins 
alone we arrive at results of some interest. 
One of the largest veins observed runs along the coast for half a 
mile or more, commencing a short distance beyond St. Anthony’s 
Castle to the southwest of the city; it is the same that has afforded 
the sections exhibited in figures 6, 7, 8. Its direction is southeast by 
south and northwest by north. Another vein in the same region 
follows a southeast and northwest direction. Over the hills south 
and southwest of the city, the feldspathic granite veins stand out in 
broken walls, the inclosing rock having been removed by decompo- 
sition and wear. Large veins not far distant run in a southeast by 
south and northwest by north course, and dip to the northward and 
eastward fifty degrees. ‘Two veins in the same vicinity have a south- 
east by east and northwest by west course, and dip nearly with the 
preceding. Another vein, four feet broad, within a fourth of a mile of 
if 
PAG 
