CHAP. IV.] ST. THOMAS TO BERMUDAS. 295 
ash, as it were, is left behind. One per cent. seems a very small 
proportion, but we must remember that it represents one ton in 
every hundred tons of material removed by the action of water 
and of the atmosphere; and the evidences of denudation on a 
large scale are everywhere so marked, that even were some por- 
tion of this one per cent. residue further altered and washed 
away, enough might still be left to account fully for the whole 
of the red earth. The vegetable soils containing a large pro- 
portion of red earth are accumulated, usually to no very great 
depth, in hollows, the fine ultimate sediment naturally finding 
its way down to the lowest point. Fig. 74 gives an excellent 
illustration of the formation of one of the intercalated beds. 
The soil of the garden, which consists of red earth mixed with 
decayed vegetable matter, rests upon limestone. The sand- 
glacier creeps over it, and it is covered by a series of beds, 
twenty to thirty feet thick, dipping at an angle of 30°. The 
water percolating through the sandstone gradually removes the 
organic matter, and the inorganic residue is left. 
Wandering about among the pretty hill-and-dale scenery of 
Bermudas, one is not at first conscious of a singular omission, 
until all at once it bursts upon him that there is not a drop of 
water to be seen anywhere—no river, stream, or lake, not even 
a ditch or a duck-pond. The heavy rain falls upon the porous 
sand-heap, and runs through it as if it were a sieve. After a 
heavy shower, it may remain for a little collected in pools along 
the beaten road, or it may rush down a steep incline; but an 
hour after the rain is over every trace of it has disappeared. 
From the whole of the islands about low-water mark being 
composed of the same porous rock, the sea-water passes through 
it horizontally as freely as the rain-water passes through it ver- 
tically ; so that up to high-water mark, and probably consider- 
ably above it, on account of capillarity, the rock is completely 
saturated. There are some marshes and ponds on the main isl- 
and, the marshes covered with a luxuriant vegetation; but in 
