Mr. Tate on Basaltic Rocks. 211 



metamorphosed, are enveloped in the basalt; and the strata, 

 broken through, have been relatively altered in position ; 

 those on the south side having been considerably upcast. A 

 calcareous shale, very fossiliferous, and a limestone beneath 

 it abut against the dyke and are metamorphosed ; and near 

 to the castle a vein of basalt penetrates the shale. This dyke 

 is seen near Fenham, on the main land ; and further west- 

 ward near Kvloe Church, where its width is from twenty 

 to sixty feet, for it widens as it descends ; in one part it 

 is covered by shattered beds of shale. It cuts through the 

 Lowick coal beds, and is traceable further westward to 

 Leitham, the whole ascertained course beiug about fourteen 

 miles. 



The Beadnell Dyke is well exposed on the coast, rising 

 like a Cyclopean wall through sandstone, limestone, shale, 

 and coal beds, whose relative position is very slightly altered, 

 but whose structural characters are greatly changed ; coal, 

 for some distance from it, is valueless ; limestone, near to it, 

 cannot be burnt into lime and shale and sandstone are in- 

 durated. The mutual transference of qualities between the 

 basalt and the stratified rocks which it penetrates, is well 

 illustrated by this dyke. Its width is generally twenty-five 

 feet, and its direction nearly from east to west (S. 85° W.) ; 

 it is traceable four miles as far as Newham Station. 



The Hoioick Dyke appears only on the coast and is remark- 

 able for its likeness to an artificial wall, and its nearness to 

 the Whin Sill ; which, however, it is not seen to join ; it is 

 only four feet wide, sloping south 85°, and having a direction 

 of E. by N. to W. by S. ( W. 80* S). 



The Boulmer Dyke, which also is only seen on the coast, 

 is one hundred feet wide, has a direction of E. by N. to W. 

 by S. (W. 80° S.) and cuts perpendicularly through the strata, 

 which are not disturbed, and but slightly changed. 



Trobe's Dene Dyke appears only underground, in the 

 eastern part of the Shilbottle Colliery, running nearly from 

 east to west (S. 85° W.), having a width of thirty-three feet, 

 and metamorphosing the strata on both sides. In the neigh- 

 bourhood of this dyke, two layers of basalt were passed 

 through while sinking for the Shilbottle coal ; one is fifteen 

 feet thick between metamorphosed arenaceous beds, but 

 divided into three layers by the intercalation of two thin beds 

 of metamorphosed shale, each about two inches in thickness. 

 The other is sixty-three feet lower down and two and-a-half 



