SOUFRIERE, AND ON A VISIT TO MONTAGNE PELRE, IN 1902. 
355 
coast-lines and the lower grounds generally, they are very accurate; but in the 
interior only the more important points, the principal mountain summits and the 
like, have had their position sufficiently determined. The rest of the country has 
apparently been sketched in more or less carefully—but many of the details as, for 
example, the courses of the smaller streams, and the number of their branches, canm)t 
be relied on. The want of a good map on a fairly large scale is a great drawback in 
geological work, and prevents the structure of the country being laid down with any 
approach to minuteness. 
This difficulty is increased by the rich mantle of tropical forest which covers all 
the surface except those parts which are highly cultivated. In the forests one may 
walk for hours along narrow winding paths, obstructed by fallen trnnks and branches, 
by the roots of the larger trees, and the tough stems of the lianas, without seeing 
any exposure except of the deep soft soil, which in a thick layer covers the rock 
beneath. The branches of the trees meet overhead, shutting out the sun and 
affording a delightful shade; but to the right and left it is impossible to see for more 
than a few yards, so dense is the vegetation. Even where in such forest paths the 
surface of the rocks is exposed, the moist climate and the abundance of decaying 
vegetation are so powerful in effecting decomjiosition, that it may l^e a very difficult 
matter to ascertain what is their nature, and impossible to obtain specimens sufficiently 
fresh for microscopic examination. The great rapidity with which the volcanic I'ocks 
weather under these conditions, and the great depth to which they are covered with 
soft earthy decomposed material, is a source of never-failing astonishment to the 
geologist, and powerfully impresses on his mind the rapidity with which denudation 
may take place in tropical countries. The rivers and streams in the lower parts of 
their courses flow, as a rule, through alluvial deposits of gravel and boulders, but in 
the higher valleys good rock exposures are more frequent, and much may be learned 
from an examination of their banks. This is, however, no easy task ; so dense is the 
growth, so frequent are cascades and waterfalls, and so numerous the large 
boulders obstructing the streams, that such exploration is a most laborious under¬ 
taking. If we add to this the difficulty of continuous exertion in a temperature 
approaching 80° F., and an atmosphere saturated with moisture, it will be seen that 
minute geological mapping is not to be accomplished under the circumstances. 
On the other hand, the broad general features of the geology of the country 
usually can be easily made out with fair accuracy. As already stated, the conditions 
are all in favour of rapid erosion. The islands are so narrow and their central 
mountain axes so high that the ground slopes steeply on each side into the sea. The 
rainfall is heavy, averaging perhaps 100 inches on the low grounds, and much greater 
at higher elevations, and it is so distributed as to produce the maximum of geological 
effect. It is greatest in the rainy season, which in most of the islands lasts from the 
beginning of July to the end of September. In the dry season there is sometimes no 
rain for days. It usually takes the form of short heavy showers which are soon 
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