110 



the claystone : it may be connected with the underlying trap vein. 

 Another, close to the boulder, 6^ feet broad, consists in the centre 

 of blue-coloured rapidly decaying greenstone, and at the sides of a 

 hard crystalline variety of the same rock, standing above the level of 

 the central parts and of the adjoining sandstone. 



73. The celebrated Corriegills boulder, under whose shadow we 

 are now resting, is of imposing dimensions, and a conspicuous object 

 from all parts of this coast. A few on the Corrie shore exceed it in 

 size ; but they are close on the edge of the granite nucleus, and we 

 may suppose it quite possible that if Groatfell " shook his giant sides" 

 under some earthquake throe, they might have been hurled head- 

 long from the summit to the sea level. Other causes must be 

 sought for the transport of this enormous mass from the parent 

 mountains ; and of others still farther removed, though of lesser mag- 

 nitude. We have already considered the only possible causes, and 

 attempted to estimate the evidence in favour of each (Arts. 59, 

 60). That to which we chiefly lean receives support from the 

 case before us. A crowd of lesser blocks surrounds the huge boulder 

 of which we speak an association much more likely to occur in the 

 case of floating ice, than of currents emanating from a centre so 

 remote. The cubical contents, and consequently the weight, are 

 very difficult to estimate on account of the irregular form. The 

 dimensions at the base are 21 feet by 12, and the height 15 feet. 

 If rectangular, it would weigh 315 tons, as 12 cubic feet of granite 

 make a ton ; but if we deduct one -third for the conical form, which 

 is a large allowance, we shall have a weight of 210 tons. 



74. South of the boat station under the farm-house of Corriegills, 

 the dikes traverse the sandstone in every possible way ; intersecting 

 one another at various angles, bifurcating, lesser ones lost in larger, 

 &c. One of them is exposed through a longer course than any other 

 dike on the coast. It runs a long way parallel to the line of the 

 shore, or almost due N. and S., till lost under the sea near Clachland 

 Point. It is fourteen feet wide, sunk under the sandstone in the 

 tideway, and sends off a branch towards the N.W., a tongue of 

 altered sandstone being at the bifurcation. 



Two pitchstone veins, one of claystone, and one of quartziferous 

 porphyry, are found on this part of the shore. The lesser pitchstone 

 vein traverses the level shore obliquely about half-way between the 

 boat station and the base of Dun-fion. Within the tideway it 

 ranges about 72 W. of N. ; then bends about 20 towards the S., 

 i. e. } runs about due W., and bends again into the former course 

 before it enters the sandstone cliff. Under high-water mark it is 



