A SUMMER RAMBLE AMONG THE HEBRIDES. 9 



in the times of even the Oolite, must have existed as a mere 

 sea-bottom ; and Kerrera, composed mainly of trap, which has 

 brought with it to the surface patches of the conglomerate, 

 must, when the conglomerate was in forming, have been a 

 mere sea-bottom also. Is it not possible, that when the 

 breakwaters were not, the Atlantic was ; and that its tem- 

 pests, which in the present time can transport vast rocks 

 for hundreds of yards along the exposed coasts of Shetland 

 and Orkney, may have been the agent here in the transport 

 of these huge pebbles of the Old Red conglomerate ] " Rocks 

 that two or three men could not lift/' say the Messrs Ander- 

 son of Inverness, in describing the storms of Orkney, " are 

 washed about even on the tops of cliffs which are between 

 sixty and a hundred feet above the surface of the sea when 

 smooth ; and detached masses of rock, of an enormous size, 

 are well known to have been carried a considerable distance 

 between low and high-water mark." "A little way from 

 the Brough," says Dr Patrick Neill, in his " Tour through 

 Orkney and Shetland, "we saw the prodigious effects of a 

 late winter storm : many great stones, one of them of several 

 tons weight, had been tossed up a precipice twenty or thirty 

 feet high, and laid fairly on the green sward." There is 

 something farther worthy of notice in the stone of which the 

 two boulders of the Dog-stack are composed. No species of 

 rock occurs more abundantly in the embedded pebbles of this 

 ancient conglomerate than rocks of the trap family. "We 

 find in it trap-porphyries, greenstones, clinkstones, basalts, 

 and amygdaloids, largely mingled with fragments of the gra- 

 nitic, clay-slate, and quartz rocks. The Plutonic agencies 

 must have been active in the locality for periods amazingly 

 protracted; and many of the masses protruded at a very 

 early time seem identical in their composition with rocks of 

 the trap family, which in other parts of the country we find 

 referred to much later eras. There occur in this deposit 



