170 Charles Maciaren, Esq., on Grooved and Striated Rocks 



Fig. 1. 



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hlk is the line of the shore, which runs east and west ; A 

 the western rock, B the eastern. A portion of the surface of 

 both rocks is grooved, and the position of the grooved surfaces 

 is highly instructive. The north-eastern face of B, from q 

 to r, which is nearly vertical in its lower part, and rounded 

 off above, is almost entirely covered with grooves, which are 

 horizontal, straight, and parallel, generally about one inch 

 broad, and so uniform and close together, as to remind one 

 of the flutings of a Doric column. They cease at r, precisely 

 at the point where the rock begins to face the north-west ; 

 and the north-west, as well as the west face, is entirely 

 ungrooved, but considerably abraded. The east face p is 

 partially grooved. The islet A presents appearances px'e- 

 cisely similar. The north face, and a portion of the east 

 end, — that is, from m to n, — are beautifully marked with 

 horizontal grooves, which entirely disappear on the part 

 fi'om n to 0. The grooving agent, then, had power to cut 

 furrows in rocks facing the ENE. and N., but no power 

 to furrow rocks facing the \\T*nW., or even NNW., — 

 so rigid and steady was its westerly motion. Could water 

 act in this way \ All the ungrooved sides of the rock are, 

 less or more, smoothed, and the roughest part is the west 

 end 0. There is one distinct groove on the top of the islet 

 3 or 4 feet long, and \\ inch broad, pointing exactly east 

 and west. 



Fig. 2. 

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The above is a view of the north face of the islet, drawn 

 shortly after the visit, from memory, and not pretending to 

 literal accuracy ; m n the grooved part, n o the ungrooved part. 

 It is a curious fact, that the most distinct grooves are in the 

 space betiveen high and loiv water. Above the high water line 

 rv tv they become fainter and fainter, till they disapj)ear. This 



