HILL: GEOLOGY OF JAMAICA. ae 
and wide reaching are the influences of solution that it must be con- 
stantly considered in a discussion of the region. 
The summit of the plateau is a roughly serrated hilly country, in- 
dented by cockpits (sinkholes), subcircular basin valleys, and deep drain- 
ageways leading to the sea. In many places the surface is marked by 
Jagged honeycombed rocks, between which grows a dense tropical foliage. 
Knife-edgod lateral salients, like those which characterize the Central 
Mountains, are missing from this topography. Steep bluffs, undermin- 
ing benches, caverns, and sinkholes abound. 
The Cockpit Country. — The origin of the ragged summit topography 
of the White Limestone Plateau, and the evolution of the numerous in- 
berior basin valleys of which they are antecedent, can be best illustrated 
by a description of “the cockpit country,” as it is locally called; this, 
with its modifications, includes the whole of the high interior portions 
of the parishes of St. Ann, Trelawney, St. James, Hanover, Westmore- 
land, Manchester, and St. Elizabeth, to the west and north of the 
Clarendon ridges, although the cockpits are limited to a rough district 
embracing tho corners of Trelawney and St. James. In the interior of 
the western half of the island the hills are sharply rounded conical 
points. Towards the coast there are long flat-topped ridges with steep 
slopes, such as the John Crow Ridge of Portland, Yallahs Ridge of St. 
Thomas, Long Mountain of St. Andrew, the Healthshire Hills of St. 
Catherine, the Portland Hills of Clarendon, and others. Still another 
type are flat-topped circular mesas with steep walls, such as occur in 
Parts of Westmoreland and Hanover. 
The cockpits are primarily deep funnel-shaped sinkholes, from which 
tho drainage percolates downward into the cavities and fissures of the 
underlying rocks. The steep acclivities of these holes ascend into 
pointed conical ‚hills. Their origin and evolution is shown upon the 
Accompanying figure. The pits vary in depth from shallow circular 
basin-like depressions surrounded by low mammillary hills (Fig. 7, 1) 
which mark the youthful stage of their formation, to deep-sided sinks 
often 500 feet in depth, denoting the acute stage of development (Fig. 7, 1). 
Both these types are common on the summit region, where there is no 
surface drainage, the water settling in pools and penetrating down into 
the soluble and open textured substructure, carrying with it lime in 
Solution and leaving behind as soil and in the cavities of the limestone 
a blood red residuum of iron and clay, as may be seen in many fine 
Vertical sections eut along the line of the newly constructed Montego 
Bay Railway. : 
