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ARE SOILS ENRICHED, IMPOVERISHED, [Part III. 
off its brow will lie at the foot of the cliff as a 
talus or shelving bank; and what was the mid 
cliff gradually becomes the sole cliff. But this 
will eventually disappear into one slope. If the 
top of the cliff is table-land, or slopes from it, 
the cliff will waste much more slowly by disinte¬ 
gration, and the action of the elements. But sup¬ 
posing such a cliff to be all of the same material, 
I think the brow has a tendency to disappear 
most quickly, possibly from a freer access and 
action of rain water in disintegration, and pos¬ 
sibly also from roots inserting themselves in cre¬ 
vices, and, by turgescence, detaching blocks bo¬ 
dily. Independently of porousness , volcanic cones 
are unlikely to have ravines or gulleys, since 
their shape tends to diffuse, instead of to con¬ 
centrate, any run of water. In fact, the ten¬ 
dency of disintegration and the wash of rain 
would be to form cones out of single hills, and 
ridges out of chains of hills, with projecting 
spurs, each spur being itself a ridge, ending in 
a half-cone : and even these ridges are so 
studded with cones as to have a serrated or saw¬ 
like outline, and to have earned the modern 
Spanish, Portuguese, and Italian name of sierra, 
or serra, and to have originated the Latin ex¬ 
pression of per juga montium ; the very name 
