212 Mr. Tate on Basaltic Rocks. 



feet thick, and penetrates, metamorphoses, and partly replaces 

 a seam of coal. These layers are probably overflows from the 

 Basaltic dyke ; for they die out towards the north, while they 

 have been followed without change in depth to within forty 

 yards of the dyke.. 



The Hampeth Dyke is large and cuts through the Shil- 

 bottle coal and limestone beds. A mile and a half south- 

 west of Shilbottle, it appears in high crags on the banks of 

 Hampeth burn, which has forced its way through this rocky 

 barrier in a narrow gorge, with basaltic cliffs on both sides 

 rising to the height of fifty feet. The width of the dyke 

 here is one hundred and fifty feet, and the direction from E. 

 by N. to W. by S. (W. 80° S.) ; the coal on both sides is 

 charred, to the distance of fifty yards. 



All the preceding dykes do not cut through strata more 

 recent than the Mountain Limestone Formation ; but some 

 of those that follow penetrate the Millstone Grit and the 

 Coal Measures. 



The Acklington Dyke, which has a general direction of east 

 by south to west by north, is seen on the coast at Bondicar ; 

 and passing through Coal Measures and the Millstone Grit, 

 it crosses the Coquet above Acklington Park, where it is 

 thirty feet wide. A dyke, in the sam« direction westward, 

 cuts through Mountain Limestone beds at Debdon, whence 

 ranging by Cartington Castle, where it cuts through a lime- 

 stone ; it extends to Clennell, approaching the porphyry of 

 the Cheviot, but not entering it. The whole course is about 

 twenty miles. 



The Causey Park Dyke, which is thirty feet wide, has a 

 direction of east to west, and cuts through Millstone Grit 

 strata. Gritty sandstones abut against the north cheek, and 

 flaggy sandstones and carbonaceous shales are on the south 

 side. 



From Hartley, on the coast, two dykes, about a mile and 

 a half apart, run parallel to each other through the Coal 

 Measures, in the direction of W.N. W., as far as a mile north- 

 ward of Cramlington. In a line with the Southern Hartley 

 dyke, is one at Bolam, cutting through Mountain Limestone 

 beds, which are metamorphosed, the coal on both sides being 

 reduced to cinder*. 



The Tynemouth Dyke, which is more allied to Greenstone, 

 or diorite, than to basalt, cuts through Coal Measures, a red 



* Hodgson's Life, vol. ii., p. 208. 



