204 ON THE REVOLUTIONS 



two sets, — that whereas in the east, these furrows have preser- 

 ved the same direction, those on the west follow directions so 

 irregular, as to baffle all arrangement, or, if any such can be 

 traced, it is found to be entirely local, and to depend upon the 

 course of the valleys, in the immediate neighbourhood. In 

 some places in the west, as near Moffat, I have met with vesti- 

 ges of ridges; but, on close inspection, I found them rounded off 

 at both ends. Even these, however, occur but very rarely, and 

 are to be expected, under the hypothesis here laid down, ac- 

 cording to which, it is reasonable to suppose, that the effects of 

 the first impulse should not be always completely done away 

 by those which followed. Also the direction of hills in the 

 west, may occasionally have been such as to produce conspi- 

 rins effects with those of the first action. 



In the neighbourhood of the Bay of Kirkcudbright, I have 

 seen two specimens of rock, dressed with furrows, very well 

 characterised, and both indicating a direction from the north ; 

 one near the porter's lodge connected with the House of Bal- 

 mae ; the other upon a rock within high water-mark, upon 

 the south side of St Mary's Isle. But the neighbouring country 

 has no corresponding character, all the loose assemblages being 

 arranged in knolls. 



On the island in Loch Doon upon the confines of Ayrshire, 

 and the stewartry of Kirkcudbright, the dressing of the rock is 

 peculiarly interesting. The island is of granite, near its junc- 

 tion with the strata; and the granite contains many shai-p an- 

 gular fragments of killas. \^liere the rock has undergone the 

 diluvian dressing, the contrast of the two substances is beauti- 

 fully displayed, the granite being of a light colour, and the kil- 

 las dark-blue. 



By the action of the air, the granite has been decomposed' 

 at the surface, and has been corroded nearly to the depth of an 



inch ; 



