Ch. X.] 
PARALLEL ROADS OF COQUIMBO. 
131 
rounded blocks. One of these cliffs appears in the hill behind 
Banos del Pujio, about 700 feet above the level of the sea, and 
200 above the contiguous valley. Another occurs at Aman- 
caes, at the height of perhaps 200 feet above the sea, and others 
at intermediate elevations. 
Parallel roads of Coquimbo. — We can hardly doubt that the 
parallel roads of Coquimbo, in Chili, described by Captain 
Hall, owe their origin to similar causes. These roads, or shelves, 
occur in a valley six or seven miles wide, which descends from 
the Andes to the Pacific. Their general width is from 20 to 
50 yards, but they are, at some places, half a mile broad. 
They are so disposed as to present exact counterparts of one 
another, at the same level, on opposite sides of the valley. 
There are three distinctly characterized sets, and a lower one 
which is indistinct when approached, but when viewed from a 
distance is evidently of the same character with the others. 
Each resembles a shingle beach, being formed entirely of loose 
materials, principally water-worn, rounded stones, from the 
size of a nut to that of a man's head. The stones are prin- 
cipally granite and gneiss, with masses of schistus, whinstone, 
and quartz mixed indiscriminately, and all bearing marks of 
having been worn by attrition under water *. 
The theory proposed by Captain Hall to explain these ap- 
pearances is the same as that which had been adopted to 
account for the analogous parallel roads of Glen Roy in Scot- 
land f . The valley is supposed to have been a lake, the waters 
of which stood, originally, at the level of the highest road, until 
a flat beach was produced. A portion of the barrier was then 
broken down, which allowed the lake to discharge part of its 
waters into the sea, and, consequently, to fall to the second 
level ; and so on successively till the whole embankment was 
washed away, and the valley left as we now see it. 
As I did not feel satisfied with this explanation, I applied to 
* Captain Hall's South America, vol. ii. p. 9. 
f See Sir T. D. Lauder, Ed. Roy, Soc. Trans., vol. ix., and Dr. Macculloch, 
Geol. Trans., 1st Series, vol. iv. p. 314. 
K 2 
