6 ON CHANGES IN THE DISPOSITION 



cessary, in this case, as in many others where they are 

 equally misapplied by those who are alarmed to find 

 them applied to the very different phenomena which 

 they have really caused. That such actions have pro- 

 duced analogous effects, there is little reason to doubt ; 

 but while it is difficult to point out the cases, we are 

 sure that the flow of water, sudden and powerful, or 

 slow and gradual, is capable of fulfilling all the con- 

 ditions: though it must not be forgotten that the 

 fractures consequent on the elevation of the strata 

 must have also produced every species of discontinuity, 

 from the simple fissure to the wider valley. Still, if 

 there be any cases which especially mark the action of 

 water, it is precisely those where this correspondence 

 of strata occurs ; since any more violent and sudden 

 cause must have disturbed this regularity. Yet the 

 want of such correspondence does not prove the re- 

 verse : since such a displacement as should destroy the 

 continuity of a set of strata, is precisely that which 

 would give access to water with all its consequent effects. 

 The cataract is generally connected with the ravine, 

 and the actions are so exactly those which must have 

 commenced from the very beginning, that it demands 

 the next consideration. The most obvious effect is the 

 retrogradation of the cascade in certain cases, with its 

 destruction in others ; as, in peculiar positions, it is 

 the production of a deep fissure, at length to become 

 a ravine, and ultimately a valley. In Scotland, the fact 

 of simple retrogradation is seen at the Cauldron linn, 

 and on the Braan at Dunkeld, where the lateral devia- 

 tion is not less remarkable than the depression of the 

 river. If the marks in these places are trifling, they 

 are instructive: but at Foyers, the excavation is as 

 striking from its depth and magnitude, as from its 

 picturesque beauty ; as Kea cloch affords examples 

 of every effect that running water can produce. And a 



