NOTES OK THE GEOLOGY OF DUNBAR SHORE. 101 



In forming the new harbour works, many of the finest columns have been 

 cut away. To get an adequate idea of them now, it is necessary to get upon 

 the sea wall of the new pier, and view them on the west side of the island, 

 beyond the wall. From this you look down upon the ends of the columns, 

 and by going a little westward along the wall, if it is low water, a consider- 

 able portion of the pillars may be seen in their length. The columns are of 

 various shapes, of three, four, and six sides; these however, arc not equal, nor 

 is their form always regularly defined, or their jointings very apparent. In 

 some instances these joints are fifteen feet in length. They seem to be formed 

 of concentric circles, which appear, when they become decomposed from exposure 

 to weather, and they are traversed by a perfect net-work of small veins of jasper 

 and quartz. The rock forms a noble breast-work to the harbour, and it would 

 have been well had the engineers who constructed the new works, had more 

 of the same sort of assistance. The long sea wall betwixt the battery and the 

 castle rock, although of considerable height, is not security enough against the 

 huge waves of the German Ocean, which, in a storm from the north-east, 

 break forty feet above it; the spray falling amid a profusion of rainbow tints 

 into the basin within. Beneath these pillars, it is stated, is a bed of Red- 

 coloured Trap-tufF, resting upon the Sandstone, through which, as we have 

 already mentioned, the castle rocks protrude. The position of these basaltic 

 columns is not quite vertical, sloping from south-east towards north-west. 

 Their colour, when fractured, is a bright red; where, exposed to the continuous 

 action of the sea, they are more yellowish, and wear away roundedly at the 

 apex; presenting, when looked down upon, an appearance somewhat resembling 

 a gigantic honey-comb, at the early part of the season^ when the larvae are 

 yet protruding from the waxen cells. 



Dr. Mc'CuUoch, in his Geology, published in 1831, vol. 1, page 172, has 

 well described these rocks, although, as pointed out by Mr. Cunningham, he 

 falls into the grave error of supposing them to be Sandstone columnarized 

 by heat; he says, ^^the columns are limited to a small space, but are of 

 considerable dimensions; attaining two feet or more of diameter, and a length 

 of fifteen feet or upwards. Where this columnar structure occurs, the 

 character of the rock is changed in a greater or less degree, becoming more 

 compact, harder, and in some places, passing into a perfect but coarse jasper; in 

 addition to this, it presents the indications of an internal concretionary structure. 

 The transverse sections of each prism are marked by concentric lines, of 

 different colours, whitish or reddish, which conform accurately to the sides 

 and angles towards the exterior, but become gradually curved as they 

 approach the centre; indicating the probable existence of a spheroidal nucleus." 



Beyond the shore rocks, there is a remarkable line of rocky islets, com- 

 mencing directly north from the Battery, at the distance of two hundred and 

 ten yards, and running westward in a curved line, till they approach the shore 

 at the Table rocks, referred to already. There are, at least thirteen of these, 

 varying in height from eight to thirty feet above low water. This chain of 



