580 CHILL 
by a large number of greenstone dikes. Much of the rock is compact, 
without any traces of crystallization; and this variety in some of the 
dikes contains minute crystals of calc spar. ‘The compact greenstone 
passes into a crystalline rock (diorite) of an olive-green colour, con- 
taining distinct acicular crystals of hornblende. 
In the “ third cuesta” on the road from Quillota to San Felipe, the 
following varieties were observed in dikes along the road. 
1. A compact dark olive-green rock, breaking with a rough frac- 
ture. It is easily cut with a knife, and is translucent on the edges, 
in which respect, as well as in general appearance, it resembles ser- 
pentine. 
2. A similar greenstone, a few rods distant, porphyritic with indis- 
tinct crystals of feldspar, which give it a dull spotted appearance. 
The disseminated crystals are about an eighth of an inch thick. 
3. Near the last, a grayish-green rock with a smooth fracture and 
a few acicular crystals of hornblende half an inch or less in length. 
In the “ second cuesta,” between Quillota and San Felipe, the rock 
constituting it undergoes remarkable variations of character. It is 
mainly composed of feldspar. Ascending from the southwestward, we 
met with: 
1. A compact graystone, having a grayish colour, in some places 
becoming slightly reddish. It contains a little epidote, of a dull-green 
colour, disseminated through the feldspar base. It breaks with a 
smooth conchoidal fracture, and is rather tough. 
2. A few rods beyond ;—a similar rock, but having a coarser tex- 
ture, and containing distinct crystals of feldspar and a few nodules 
of chlorite. 
3. A few rods beyond ;—the rock is more epidotic and contains a 
larger proportion of chlorite nodules: it is also more porphyritic than 
No. 2. The colour varies, as we proceed, to a brownish-purple. 
A. Farther up the ascent;—the same rock as the last takes a brown- 
ish-red, or even a brick-red colour, and is delicately porphyritic ; 
the epidote occurs crystallized in small geodes, an inch or so in dia- 
meter ; and other geodes contain minute quartz crystals : these geodes 
are very numerous. ‘The epidote crystals are about a fifth of an 
inch long, and have the usual pistachio-green colour. 
This variety continues along for several rods, with little variation 
except in the shade of red colour, which in some places is very deep 
and brownish. 
5. At the summit, the rock is brownish-black and very compact and 
