322 Tlie Philosophical Society of Glasgow. 



surface of the pavement is formed by the tops of the columns ; each 

 column h^ a regular shape ; the edges are slightly worn, giving each 

 stone a rounded appearance, the whole having the look of a mosaic pave" 

 ment. This pavement is also an overflow of a depth of from four to five 

 feet, the columns having been formed, as stated in the former paper, 

 by rapid cooHng. Under this pavement is found a thin layer of 

 trap slate, lying horizontally, and in fragments formed evidently by 

 deposition, which hes on the top of another large bed of fine-grained 

 trap. So that we have first and lowermost a bed of trap ; whether this 

 has been also an overflow was not positively ascertained ; but it is 

 more than probable, from its having also a sort of columnar appearance, 

 the columns standing perpendicular ; then we have a thin bed of slate, 

 varying in thickness from three inches to eighteen; then over this 

 is the trap pavement just referred to, which forms a miniature of the 

 Giant's Causeway. After passing this pavement, and keeping by the 

 sea-line, there occurs again the regular series of dykes, interrupted by a 

 large sand-beach, passing which we come to the level rock-beach, in front 

 of the village of Whiting Bay, where the dykes are seen protruding 

 through the sandstone rock in aU shapes and forms, and intersecting 

 and crossing one another at different angles ; but with one or two 

 exceptions, such as where a dyke runs between, and joins two other 

 dykes, they all run in a line less or more direct from the land to the 

 sea. Many of the dykes divide and branch off into several parts, some 

 of which terminate within a few yards of the main dyke ; but most of 

 them continue their course towards the land. 



At the south end of the bay there rises a rugged mass of trap 

 within the tide-mark, and from this point may be traced, at a few 

 yards distant, several small dykes running either to or from it. When 

 we meet with such a mass of trap, rising far above the rocks around it, 

 and see dykes apparently emanating or radiating from it, we may 

 reasonably conclude that the dykes have been formed in consequence 

 of the upheaval of the mass, causing the solid rock to crack round 

 about it, the fissures being filled up by the fused mass. But this is 

 somewhat different from those level dykes branching off into radiating 

 arms. By a careful examination of some of those dykes and their 

 branches, it was found that the sandstone between the arms branch- 

 ing off were masses of sandstone resting upon and imbedded in 

 the trap, and not connected with the parent rock ; it is therefore 

 probable that during the great upheaval of the trap-hills in the 

 neighbourhood, the sandstone got shattered, and the trap not only 

 flowed up into the cracks, but spread horizontally, lifting up large 

 masses of fractured sandstone. The sandstone on the top of this 

 overflowed mass of trap is partially worn away by the sea, exhibiting 



