BASALTIC DYKE. 17S 



Along with the basalt, we find, in some parts of the dyke, that 

 clayey substance known by the outlandish name wacke. It is usually 

 of a greenish grey or light olive colour, with some ferruginous stains, 

 especially in the seams or cracks, with which it abounds. Some of 

 these cracks are filled with calc spar. It is generally rather soft and 

 friable, but often occurs hard and compact. In short, it bears a strong- 

 resemblance to the indurated clay accompanying the gypsum at the 

 mouth of the Tees, but does not like that effervesce with acids, and 

 has a more coarse and earthy aspect. It is found among the blocks 

 of basalt in patches, or irregular veins. A vein of wacke, three or 

 four feet wide, occurs in Stainton quarry ; where the authors also 

 observed some of the most interesting varieties of the basalt. 



As such dykes are known to be connected with breaks or slips 

 in the strata, it is natural to expect, that in some parts of this long 

 ridge, there will be found obvious marks of dislocation. This is the 

 case at Cockfield, where the strata on the south side of the dyke are 

 three fathoms higher than the corresponding strata on the north side.. 

 Had we access to examine the strata on both sides of the dyke, in its 

 progress through our district, we might probably discover a number, 

 of similar phenomena, particularly about Cliffrigg, and at May- 

 becks, at both which places there are indications of breaks. At 

 Maybecks, the dyke terminates abruptly on arriving at a stream, the 

 channel of which seems to have been produced by a break, the 

 ground on the east side being considerably higher tlian that on the 

 west. We have discovered no traces of the dyke from thence to the 

 shore ; but as it bears somewhat in the direction of Peak, or more 

 nearly in that of Haiburn wyke, it may be connected with the slip at 

 one of these places. We have not perceived what effect it has had 

 on the great break in the vale of the Esk, which river it crosses a 

 little above Egton bridge. 



It is well known, that where a basaltic dyke passes through; 



