Summary of Geological Observations. 
Towards 9,000 feet the persistently humid climate gives rise to the zone 
of the cryptogams, and to the bogs that constitute one of the characteristic 
features of Ruwenzori. From this altitude, we may say right up to the 
glaciers, the ground is everywhere uninterruptedly covered with a boggy peat- 
turf layer which not seldom reaches or exceeds a thickness of 20 inches. On 
this substratum is developed a vigorous vegetation of mosses, hepaticae 
(liverworts) and lichens, which spread a thick mantle over the protruding- 
rocks, the erratic boulders and the trunks of the trees, whether living or fallen 
with age, and for centuries accumulating on the surface of the ground. 
Over this overlying stratum of bog and vegetable detritus there is but 
a slight How of water, absorbed as it is as by a huge sponge. The surface 
layer thus forms a protecting carpet for the rocks which, when they can be 
seen underneath, appear to be relatively intact, escaping as they do in great 
measure from the erosive phenomena. 
Beyond the boggy zone the surface action of the meteoric agents comes 
again into play, but it must act very slowly in consequence of the abundant 
vegetation of the crustaceous lichens covering the rocks. The nature of these 
rocks, largely constituted of amphibole and quartz, also explains the slighter 
action of atmospheric denudation which has freer play in the gneiss and 
mica-schist zone. 
Attention may again be called to the characteristic protrusion of the rocks 
composed of more resisting elements. This fact is apparent in the beds of 
garnet-bearing rocks, where the large crystals of garnet protrude with an 
almost variolar or pitted aspect. The phenomenon is typical also in the mica- 
schist zone on the western slope of Mt. Baker, where the mica-schist is 
associated with abundant quartz in lenticular veins and thin layers which 
everywhere form protuberances, sometimes even very conspicuous on the 
surface of the ground. 
Lastly, in the higher zones to the modifying and erosive action of the 
atmosphere is added the extremely potent factor of frost and thaw. In this 
case, wherever the underlying rocks are not protected by the masses of ice, we 
find long stretches of ground covered with loose chaotic and shifting detritus 
analogous to what is noticed on the crests and higher slopes of our Alpine 
heights. 
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