329 
i88i.] Scepticism in Geology . 
now flowing through them, not allowing sufficiently for the 
excavating and transporting power which the waves of the 
ocean exert on land during its emergence,” and to “ those 
inequalities of the surface which must be produced by 
movements accompanying the upheaval of the land.” Lyell 
is, in fa< 5 t, criticised by Colonel Greenwood, in “ Rain and 
Rivers,” more after the fashion of a warrior than a philoso- 
pher, because he attaches too little importance to the 
“ perpetual disintegration, denudation, and destruction ” 
which is produced by rain and rivers ; the Colonel holding 
the reverse opinion to “ Verifier.” 
In the volume already referred to, I have shown how im- 
probable it is that the present bed of the St. Lawrence has 
been formed solely by water erosion ( see “ Constitution of 
the Earth,” pp. 300 to 303). “Verifier” argues that the 
retrocession of Niagara Falls arises from the fact that the 
St. Lawrence flows over a bed of limestone go feet thick, 
between which lie soft shales of equal thickness ; the splash 
of spray wafted up from below the Falls dissolves the soft 
shale, and the hard limestone breaks away by its own weight. 
But he overlooks the fact that Lyell, during a visit to the 
Falls, “ obtained geological evidence of the former existence 
of an old river-bed,” which he had no doubt indicated the 
original channel through which the waters once flowed from 
the Falls to Queenstown. Why did the St. Lawrence leave 
its ancient bed to form a chasm go feet deep, through the 
hard limestone ? I have suggested that, under the acftual 
circumstances, running water could produce no such effect, 
but that the change in its course must have been due to a 
disturbance of the crust of the Earth consequent upon 
internal expansion. “ Verifier ” in this instance abandons 
his theory that river-beds have originated in a primeval 
split-up of the crust of the globe consequent upon contrac- 
tion and shrinkage whilst it was cooling down from a molten 
condition. It is clear that the fissure through which the 
St. Lawrence passes cannot have originated “ in events, 
issues, and developments which have passed away,” or “ on 
a different condition of our planet from the present ;” the 
ancient water-course showing that, long before the existence 
of the one down which the water now passes, the sur- 
face of the Earth did not differ greatly from its present 
condition. 
“ Verifier ” refers most successfully to the great cataradt 
of the Zambesi, in Central Africa, as an example, on the 
largest scale, of a river-bed made for the river and not by it. 
“ This commanding stream having attained a width of more 
vol. hi. (third series). z 
