by the elevation and remain generally in
very narrow channels.

East of Cardenas the general elevation of the plain is low, sloping
gradually both north and south from the axis of the island. Considerable
areas of this plain are found among the various mountain groups in the
eastern half of Santa Clara province, beyond which it extends over the
greater part of Camaguey and into Oriente. Here it reaches the northern
coast between isolated mountain groups, extending as far east as Nipe
Bay, and toward the south, merges into the great Cauto Valley.

From Cabo Cruz the plain extends along the northern base of the Sierra
Maestra to the head of the Cauto Valley. Its elevation near Manzanillo
is about 200 feet, whence it increases to 640 feet at El Cristo. In the
central section of Oriente, the Cauto River and its tributaries have cut
channels into this plain from 50 to 200 feet in depth. In the lower part
of the valley these channels are sometimes several miles across and are
occupied by alluvial flats or river bottoms. They decrease in width
toward the east and in the upper part of the valley become narrow
gorges.

A large part of this plain of Cuba, especially in the central provinces,
is underlaid by porous limestone, through which the surface waters have
found underground passages. This accounts for the fact that large areas
are occasionally devoid of flowing surface streams. The rain water sinks
into the ground as soon as it falls, and after flowing long distances
under ground, emerges into bold springs, such as those of the Almendares
that burst out of the river bank some eight miles south of the City of
Havana. Engineers of the rope and cordage plant, just north of the City
of Matanzas, while boring for water, found unexpectedly a swift, running
river, only ten feet below the surface, that has given them an
inexhaustible supply of excellent water.

Most of the plains of Cuba above indicated have been formed by the
erosion of its surface, and are covered with residual soil derived from
the underlying limestones. Where they consist of red or black clays they
are, as a rule, exceedingly fertile. Certain portions of the plains,
especially those bordering on the southern side of the mountains of
Pinar del Rio, are covered with a layer of sand and gravel, washed down
from the adjoining highlands, and are, as a rule, inferior in fertility
to soils derived from the erosion of limestone. Similar superficial
deposits are me