Part III.] OR POISONED BY VEGETABLE GROWTH? 
189 
of hills being taken from the yoke-like appear¬ 
ance of contiguous cones. 
For this reason, though, as Sir Humphrey 
Davy finely remarks, no work of a mortal can 
be immortal, those works of man which ap¬ 
proach nearest to immortality are cones,—the py¬ 
ramid, the tumulus, and the cairn. Why do 
the imber edax and the fuga temporwn pass 
with so light a touch over these ? Because they 
begin with a form which others end in,—a form 
which is not deformed even by disintegration 
and the wash of rain. 
In comparison to the broad waste from the 
wash of rain, the waste by the direct action of 
rivers may be reckoned as nothing; and even 
this waste by the direct action of rivers takes 
place, I might say, entirely when they are 
flooded by rain. The real main geological work 
of rivers is indirect; that is, the carrying off the 
traffic brought to them by the wash of rains : 
and they carry this mighty traffic for the entire 
terrestrial surface of the globe; at least, their 
channels do. 
And the channels of most rivers would exist 
whether the rivers existed or not, as in the 
south you constantly see river beds dry, or al¬ 
most dry, except when filled by the superficial 
