Geological Origin of the Present Scenery of Scotland i i 



In short, the valleys must be the work of the rains and streams 

 which flow in them. " If, indeed," says the profound and elegant 

 Playfair, " a river consisted of a single stream without branches 

 running in a straight valley, it might be supposed that some great 

 concussion or some powerful torrent had opened at once the 

 channel by which its waters are conducted to the ocean ; but, 

 when the usual form of a river is considered, the trunk divided 

 into many branches, which rise at a great distance from one 

 another, and these again subdivided into an infinity of smaller 

 ramifications, it becomes strongly impressed upon the mind, that 

 all these channels have been cut by the waters themselves ; that 

 they have been slowly dug out by the washing and erosion of the 

 land ; and that it is by the repeated touches of the same instru- 

 ment that this curious assemblage of lines has been engraved so 

 deeply on the surface of the globe." 



But it may be objected, that surely the deep ravines and gorges 

 of the country are proofs of great yawning gaps having been opened 

 by rendings of the solid ground. Such defiles, for instance, as 

 those of the Clyde below the Falls, or of the Ayr at Barskimming, 

 it may be contended, must plainly be due to subterranean move- 

 ments. Now, paradoxical again as the statement may seem, it is 

 precisely in such narrow gorges that the reality and potency of the 

 action of water in scooping out hard rock is most strikingly seen. 

 How much soever these narrow, dark, chasm-like ravines may 

 recall the effects of earthquake shocks, they can be easily shewn to 

 have been excavated entirely by the streams which flow in them. 

 A mere tyro in geology who has learned to trace out the line of a 

 single stratum, can follow the beds of rock from side to side of a 

 ravine, and across the bottom, and satisfy himself that no fault or 

 yawning earthquake-rent had anything to do with the formation of 

 the ravine, but that the process has been entirely one of excava- 

 tion. I am tempted here to make one other quotation from 

 Playfair, who, in reference to the gorges of large rivers in moun- 

 tainous regions, remarks : — " There is no man, however little 

 addicted to geological speculation, who does not immediately 

 acknowledge that the mountain was once continued quite across 

 the space in which the river now flows ; and if he ventures to 

 reason concerning the cause of so wonderful a change, he ascribes 

 it to some great convulsion of nature which has torn the mountain 

 asunder, and opened a passage for the waters. It is only the 

 philosopher who has deeply meditated on the effects which action 



