Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne (1867).djvu/47

Rh east, and is traceable a distance of 7 miles, passing, in its course, also through Mountain Limestone strata. On the Tweed it is 10 feet wide, but it thickens eastwards, and at Melkington it is 15 feet, and at Mattalees 33 feet wide.

The Lindisfarne Dike has a course from eastward to westward, but not straight. It crosses the south part of Holy Island in the direction of south 85° east, and is seen two miles seaward, forming the Plough and Goldstone rocks, on which the Pegasus was wrecked. On the west side of the island the dike is exposed in a high cliff, and is there 120 feet wide, with a slope to the south of 95°; large blocks of limestone are enveloped in the basalt and highly metamorphosed, and the strata have a considerable upcast on the south side. A calcareous shale, highly fossiliferous, lying above a limestone, is remarkably metamorphosed—and near to the Castle veins of the basalt penetrate the shale. This dike is seen near Fenham, and afterwards a little northward of Kyloe church, where it has a direction of S. 80° W., and is from 20 to 60 feet wide, increasing in width as it descends; and in one part it is covered by sandstones and shales. It cuts through the Lowick coal field and is traceable westward to Leitham, the whole ascertained course being about 14 miles.

The Beadnell Dike is well exposed on the coast, rising like a Cyclopean wall through sandstone, limestone, shale, and coal beds, whose relative position is but slightly altered, but whose structural characters are greatly changed: coal for some distance from it is valueless, limestone near it will not burn into lime, and shale and sandstone are indurated. The mutual transference of qualities, between the basalt and the stratified rocks penetrated, is well illustrated in this dike. Its width is generally 25 feet; the direction is south 85° west; and it is traceable four miles inland as far as the Newham Station.

The Howick Dike is only 4 feet wide, sloping south 95°, and with a direction of north 80° east. It is seen only on the coast, and is remarkable for its wall-like appearance and its nearness to the Whin Sill, which, however, it is not seen to join.