lying single or piled in heaps, but all arranged in nearly straight
lines.); in other parts, of a red sandy clay, often with an admixture of
pumiceous matter. Although these basins are connected together like a
necklace, in a north and south line, by smooth land-straits, the streams
which drain them do not all flow north and south, but mostly westward,
through breaches worn in the bounding mountains; and in the case of the
second basin, or that of Rancagua, there are two distinct breaches. Each
basin, moreover, is not drained singly; thus, to give the most striking
instance, but not the only one, in proceeding southward over the plain of
Rancagua, we first find the water flowing northward to and through the
northern land-strait; then, without crossing any marked ridge or watershed,
we see it flowing south-westward towards the northern one of the two
breaches in the western mountainous boundary; and lastly, again without any
ridge, it flows towards the southern breach in these same mountains. Hence
the surface of this one basin-like plain, appearing to the eye so level,
has been modelled with great nicety, so that the drainage, without any
conspicuous watersheds, is directed towards three openings in the
encircling mountains. ((It appears from Captain Herbert's account of the
Diluvium of the Himalaya, "Gleanings of Science" Calcutta volume 2 page
164, that precisely similar remarks apply to the drainage of the plains or
valleys between those great mountains.) The streams flowing from the
southern basin-like plains, after passing through the breaches to the west,
unite and form the river Rapel, which enters the Pacific near Navidad. I
followed the southernmost branch of this river, and found that the basin or
plain of San Fernando is continuously and smoothly united with those
plains, which were described in the Second Chapter, as being worn near the
coast into successive cave-eaten escarpments, and still nearer to the
coast, as being strewed with upraised recent marine remains.

I might have given descriptions of numerous other plains of the same