Part III.] OR POISONED BY VEGETABLE GROWTH ? 
199 
“ R-esolutaque tellus 
In liquidas rorescit aquas,” 
and 
“ Tellus glomerata cogitur unda,” 
are as true at this instant as in the time of Py¬ 
thagoras, or as they have been and will be, shall 
I say ? evermore. 
But in reference to the marine theory in 
general, that the action of waves on land 
slowly emerging from the deep should have 
a tendency to wash away soft parts and to 
leave hard parts, I can conceive: but to attri¬ 
bute the formation of our valleys to this cause, 
as Lyell does, is to suppose that the materials of 
all the valleys running from the tops of all the 
heights on the globe were originally softer than 
the materials of the intervening ridges; but in 
almost all cases we can see that this is not so, by 
the corresponding strata on the opposite sides of 
valleys. 
In regard to currents: a current might de¬ 
capitate a continent as it rose, supposing equal 
softness of materials, or it might scoop a hori¬ 
zontal groove of any size or depth, or (granting 
lines of hard intervening ridges) many grooves; 
but they must all be horizontal, and in one di¬ 
rection. No marine current could make a single 
o 4 
