566 CHILL 
eighth of an inch. The rock each side of the vein is in most instances 
discoloured for three-fourths of an inch or more. 
a. This discoloured portion sometimes partakes of the green colour 
of this mineral from impregnation with it, and occasionally when so, 
the walls of the vein have a compact structure, a dark polished surface, 
and a dull green colour. 
6. In other cases, the adjoining rock has a rusty or half-decomposed 
aspect, and the mica, which is elsewhere black, is here altered to a 
dull brownish colour. 
c. In the majority of instances, however, especially when the rock 
traversed is feldspathic, the gray or white of the feldspar is changed 
to a deep flesh-red, or brick-red. The feldspar has evidently re- 
ceived this tint from its proximity to the epidotic vein, and it is due 
beyond doubt to oxyd of iron, one of the constituents of epidote. In 
many places where the seam of epidote can scarcely be distinguished 
on account of its minuteness, its position is marked by this flesh-red 
band. 
These epidotic veins occur both in the granite, gneiss, and syenite, 
and they have the same characters in all these rocks. They also 
intersect the veins of granite, and it is especially through these veins, 
that the flesh-red bands are most distinct. In many places, epidote 
forms the walls of these veins; again, it is found running irregularly 
through them in various directions, and crystallizing where in favour- 
able positions; again, it enters apparently into the constitution of the 
vein, so as to forrn a compound rock of epidote and feldspar, the feld- 
spar having throughout a deep flesh-red colour. ‘There are instances 
of feldspar which is flesh-coloured, though not containing epidote ; yet, 
in such cases, veins of epidote are always abundant in the vicinity, 
and frequently intersect the granitic vein. 
Neat crystallizations of epidote were not observed, though imperfect 
and minute crystals were not rare. ‘The epidotic veins contain no 
foreign mineral excepting feldspar, and in these instances we have 
considered them feldspathic veins with walls of epidote. In one 
instance the feldspar constituted less than half the width of the vein. 
There is no uniformity of direction in these veins; they cross very 
irregularly, and many disappear after continuing for a few feet. 
Figure 4 is a map of the veins on the surface of a block of syenite 
but ten feet square, observed on the coast near the Valparaiso light- 
house. The rock has a dark colour, and contains a large proportion 
of black hornblende. ‘These veins, so various in direction, have the 
