140 THE NATURAL HISTORY OF AILSA CRAIG. 



nor boulders foreign to the island, nor am I acquainted with any 

 records of any ; x but the well-known caligraphy of that period can 

 still be distinctly traced on the east face of the rock, the glacial 

 striae running in a horizontal direction along the smoothed and 

 ice-worn surface of the syenite, and reaching to perhaps 500 feet 

 above sea-level ; the upper half of the surface of the Craig being 

 much more broken up by weathering than the lower. During the 

 glacial period Ailsa syenite has been dispersed to considerable 

 distances, and it is found in the Isle of Man. The raised-beach 

 period is well represented on the east side by the great bank of 

 very coarse shingle composed of syenite blocks and pebbles, with 

 a few of dolerite from the dykes, and by some old caves at the 

 north end. These caves are mostly in the lines of trap-dykes, but 

 the Water Cave has been excavated in the solid syenite. The 

 material composing this great bank of shingle cannot have been 

 derived from the east side of the island, as the old sea-cliffs 

 there are but feebly, or not at all, represented, and it has evidently 

 been brought mostly from the south, partly from the north end, 

 and as many of the blocks are over one foot in diameter this gives 

 us some notion of the turmoil which must take place during storms. 

 A number of years ago an immense fall of rock occurred at the 

 south end during a thunder storm. This must have often taken 

 place on Ailsa, and will continue to do so till the whole island has 

 fallen into the sea, the rock being ground up by the ocean-mill 

 into pebbles, sand and mud, and carried off by the currents. The 

 high cliffs on the west and south sides were probably, in great 

 part, produced by the waves during raised-beach times, but the 

 beaches or rock-beaches themselves have now been obliterated. 

 The west cliff is said to reach to about 300 feet in height, and in 

 that respect closely resembles the great raised-beach cliff at 

 Goldenberry Head near Portincross, and gives us a vivid idea of 

 the immensely long period of raised-beach time. The raised- 

 beaches of both Wigtownshire and Ayrshire contain plenty of Ailsa 

 syenite pebbles, and they are often to be seen on the present 

 shores of the mainland. 



The deposits in Garry Loch are known to be 17 feet deep, 

 and it would be interesting to ascertain if this hollow had been 

 excavated in the rock or the loch merely formed by a detrital dam. 



1 See, however, B. XVI. 154, where Mr. MacCartney gives a description 

 of a deposit of boulder-clay which he found (Ed.) 



