202 ON THE REVOLUTIONS 



In that district, the straight and parallel ridges, so universal 

 in this neighbourhood, and the forms of craig and tail, such as 

 that of Edinburgh Castle, nowhere occur. The same assem- 

 blage of substances assume a different form, and present to 

 view a perpetual succession of knolls, equally round at both 

 extremities. This arrangement is conspicuous in the neigh- 

 bourhood of Gilsland, which is surrounded with knolls of this 

 description. It was there that a theory occurred to me, to ac- 

 count for the contrast of the opposite side of our island, which 

 I have never since had occasion to alter, having found that it 

 gained ground by every new observation. I have, in particu- 

 lar, observed these forms to prevail exclusively in the valleys 

 of Carlinwork, of Dumfries, and of Kirkcudbright. I imagined, 

 that the diluvian wave had flowed at some remote period from 

 a westerly or north-westerly direction, and had broke over our 

 island ; that its magnitude, though perhaps far short of the al- 

 pine stream, had been such, that a great body of its water 

 crossing the ridge of country which separates the two coasts, 

 overwhelmed the district in the neighbourhood of this city, dis- 

 charging itself into the German Ocean. But that another por- 

 tion of the wave, being retained by that ridge of country, and 

 being left to follow the impulse of gravitation, when the supe- 

 rior water flowed on, had returned again upon the countries 

 which it had just crossed, like the back-draught of a common 

 wave. By watching the operations of a high sea, breaking upon 

 a rapidly shelving beach, covered with coarse gravel, we may 

 iorm some judgment as to the influence of such a back-draught ; 

 the sound produced by the blocks of stone grinding upon each 

 other, as the wave retires, conveys a strong idea of the corro- 

 sion which must take place in such circumstances. Our East- 

 ern coast would thus be exposed to a single diluvian action, 

 whereas that on the West would undergo two in succession, 



and 



