356 
DRS. T. ANDERSON AND J. S. FLETT ON THE ERUPTIONS OF THE 
over and leave the streams in raging flood, and not unfrequently an inch of rain 
falls in an hour, and a rainfall of several inches in a day often takes jDlace. This is 
sufficient to make streams which are usually quite dry, rise and overflow their banks 
in floods which swee]3 everything before them to the sea. Even the smaller brooks, 
which are often dry in fine weather, have their channels filled with very large 
boulders, 8 feet or more in diameter, which show by their rounded and worn 
surfaces tliat they have been ti’ansported for some distance. When we remarked 
this to one of the iDlanters in St. Vincent, he gave us numerous instances in which 
streams a})parently of trifling size had moved large rock masses, and had done 
great damage to bridges, retaining-walls and other structures. Engineers have 
encountered great difliculties in making roads through the British colonies to with¬ 
stand the devastation occasioned by the heavy rains. All the less important 
thoroughfares and the bridle-paths are frequently rendered impassable by the water 
cutting across the road and washing out deep channels. These are then filled up by a 
band of labourers with large hoes, who dig up the soft rotten rock from any con¬ 
venient spot by the road side and cast it into the furrows, some of them 6 or 10 feet 
deej^. 
These deluges of rain not only greatly increase the cutting power of the streams, 
hut they also saturate the soil and render it particularly liable to slip when it is 
lying on steep ground. Much of the ground under arrowroot cultivation on the 
leeward side of St. Vincent lies on the side of ridges and slopes at angles approaching 
40°. When the plants have been dug up and the surface is left nearly hare, a few 
showers of heavy rain may cause extensive landslips, and the planter may have all 
the valuable soil stripped from a considerable part of a field in a few minutes. So 
deep and narrow are the valleys, that on each side the material is resting practically 
at the angle of repose, and anything which facilitates interstitial movement or lessens 
the cohesion of the j^articles, is sufficient to cause a landslide. Thus it will be readily 
understood that in a typical Caribbean valley the experienced eye can perceire how 
every feature of the surface is determined by the underlying geological structure. 
The coulees of lava stand out as vertical cliffs, which give foothold to only a few 
scattered j^lauts which have managed to take root in the crevices and cracks. The 
columnar jointing, though often rude, is usually sufficiently pronounced to yield 
characteristic surfaces, and to indicate the nature of the rock from a distance. This, 
however, is not always a safe criterion, for it is possible to find beds of tuff which 
weather in much the same way. As a whole, the tuffs are softer and crumble more 
readily than the lavas, yielding abundance of loose material which gathers in sloping 
taluses on the flanks of the valleys. These weathered ash beds form rich soils, and, 
where possible, are cultivated ; hut even in the higher elevations, where there is little 
cultivation, they are clothed with luxuriant vegetation, and contrast strongly with 
the bare cliffs of lava. 
In most of the islands the coast sections are very fine, and as it is possible to row 
