428 Mr. Winch on the Geology of Lindisfarn. _ [Dxc. 
island consists chiefly of greywacke pebbles, washed down from 
the mountains of Selkirkshire, and deposited in their present 
situation by the current of the river Tweed. For this informa- 
tion, I am indebted to a friend,* thoroughly acquainted with the 
geology of the border. The diluvium covering the southern 
division of the island constitutes a tolerably fertile soil, though 
sand appears to predominate : mixed through it, are water-worn 
masses and boulders of granite, porphyry, syenite, greywacke, 
conglomerate, encrinal limestone, basalt, and sandstone, the 
produce of distant mountains, as well as of its own rocks. 
The centre of the island presenting but few points for geolo- 
gical investigation, it is my imtention to commence by describing 
the rocks forming the cliffs and beach, beginning with the south 
side of the island, and passing along its eastern return by its 
western shores. By this mode of survey, a ridge or overlying 
mass of basalt will first come under consideration; it may be 
observed on the main at Kyloe Crags, takmg a south-easterly 
direction, and again makes its appearance at St. Cuthbert’s 
Island or Hobthrush, where its elevation is inconsiderable. At 
the western extremity of the Heugh, it forms a ridge 45 feet in 
height, by 120 feet in breadth, but at the distance of 500 yards 
is lost under water. Near the eastern extremity of the basin, or 
small harbour, it again rises in irregular columns to the height of 
105 feet, and on these stands the castle. Further to the south- 
east, the stables were built on a similar rock ; and finally the 
basalt may be traced in this direction to the Plough and other 
detached rocks visible only when the tide is passed half ebb. 
This basalt is generally of an iron-grey colour, and fine-grained 
texture, occasionally with specks of pyrites, but at the foot of 
the cliffs of the Heugh its fracture becomes earthy, and specks 
of calcareous spar are scattered through it. That this line of 
eminences is not a dyke protruding above ground is clearly 
proved by the basalt resting on limestone and shale at the north- 
western part of the Heugh; on shale, a little eastward of the 
path, which crosses that ridge; and again on limestone near the 
castle. Though the regular dip of the stratified rocks is to the 
south-east, yet the edges of the stratum of limestone where it 
comes in contact with the basalt, near the boat houses, rises 
rapidly, and in part rests against it; fragments of limestone 
appear also to be included in the body of that rock; but on the 
beach at an inconsiderable distance from the Heugh, the lime-~ 
stone follows its regular course. The colour of the limestone, 
where it approaches the basalt, is pale ash-grey, its texture 
crystalline, and it contains iron pyrites and small veins, turned 
red by the oxidation of their iron. Ata distance from the basalt, 
the limestone is of a dark smoke-grey colour, splintery fracture, 
* Matthew Culley, Esq. of Akeld. 
