139 



Near the summit level of the road between north and south 

 Sannox, arid a little to the north of Sannox house, the sandstone 

 strata, on the east side of the road, are marked with striae, rendered 

 somewhat fainter than those on the slate by the effect of decompo- 

 sition. Like these they are transverse to the laminae, and are 

 directed 5 S. of W. (70 W. of magnetic N.), that is, in the 

 direction of the ridge of Suithi-Fergus. If we assign their origin 

 to ice, then we must admit that the moving masses advanced in parallel 

 courses, in both cases, from high ground on the west. 



We are now within a few yards of the spot where the finest view 

 of Glen Sannox is obtained, and to which a former excursion brought 

 us. Taking another survey of the grand scene in its evening aspects, 

 we press forward to Corrie, to catch the Clyde steamer on her way 

 to Brodick. 



EXCURSION IX. 

 To HOLT ISLE. 



96. MAKE choice of a day when it is high water about noon, and 

 leave Invercloy for Lamlash by the mail steamer from Ardrossan. 

 The captain, whose polite attention to all visitors is well known, 

 will land you at the wooden pier on Holy Isle, and on reaching 

 Lamlash, will order a boat to fetch you to the mainland at any 

 given time. A few hours will suffice to examine the island and 

 ascend the mountain. The basis of the isle all round is sandstone, 

 which rises to the height of 100 to 150 feet ; the rest of the moun- 

 tain, to the height of 1,020 feet, is composed of claystone, so that 

 this rock has the thickness of about 850 or 900 feet. On part of 

 the east side, however, it is much less than this, as the sandstone rises 

 there much above its usual height. The rock is of igneous origin, a 

 member of the trap family, and varies in structure from a soft clay- 

 stone to a compact felspar ; the harder varieties are called clinkstone. 

 As in most traps, the prevailing form is prismatic ; and on the 

 E. and S.E. sides of the island, columns of great length appear in 

 the high precipices. But the schistose structure is also common ; 

 and, as in cases already mentioned at Corriegills, both structures 

 occur in the same mass, the slaty fracture being at right angles to 

 the axis of the prisms ; the ends of the prisms first divide into 

 laminae, and the mass gradually assumes the slaty structure. The 



