CHAP. IV. ] ST. THOMAS TO BERMUDAS. 293 
remain permeable to water, and soluble, so that this process of 
solution and deposition of cement in the interstices of the stone 
goes on constantly. The extreme result is a compact marble- 
like limestone, in which the grains of sand are combined in a 
continuous magma with stalagmite or travertine. 
This dissolving and hardening process takes place irregularly, 
the water apparently following certain courses in its percola- 
tions, which it keeps open, and the walls of which it hardens; 
and in consequence of this, the rock weathers most unequally, 
leaving extraordinary rugged fissures and pinnacles, and piling 
up bowlders, the cores of masses which have been eaten away, 
more like slags or cinders than blocks of limestone. The ridge 
between Harrington Sound and Castle Harbor is a good exam- 
ple of this. It is like a rockery of the most irregular and fan- 
tastic style, and there seems to be something specially produc- 
tive in the soil, for every crack and crevice is filled with the 
most luxuriant vegetation, massing over the stones and strain- 
ing up as tier upon tier of climbers, clinging to the trees and 
rocks. Frequently the percolation of hardening matter, from 
some cause or other, only affects certain parts of a mass of rock, 
leaving spaces occupied by free sand. ‘There seems to be lit- 
tle doubt that it is by the clearing-out of the sand from such 
spaces, either by the action of running fresh water or by that 
of the sea, that those remarkable caves are formed which add 
so much to the interest of Bermudas. 
Wherever, throughout the islands, a section of the limestone 
is exposed of any depth, it is intersected by one or two horizon- 
tal beds of an ochre-like substance, called locally “red earth ;” 
and the same substance is met with in greater purity in cracks 
and pockets all through the limestone. This red earth, mixed 
with varying proportions of decayed vegetable matter and coral- 
sand, forms the surface layer of vegetable soil. As Smith says, 
when this red earth is pure, the soil is inferior; when it is black 
—that is to say, when it contains much decomposed vegetable 
