204 Mr. Tate on Basaltic Rocks. 



castle. The basalt^ which is upwards of fifty feet in thick- 

 ness, is seen in the cliff underlaid by sandstones, coal, and 

 shales ; and on the shore is a remarkably contorted limestone, 

 which is thrown into saddle ridges, and then dips awayE.S.E. 

 with other strata under the basalt. Here and there patches 

 of metamorphosed shale and sandstone are seen overlying or 

 filling fissures in the basalt ; in geodes of which are crystals 

 of quartz, some colourless, others amethystine, locally called 

 Dunstanburgh diamonds. A gut in the basalt, on the east 

 side, is called the Rumble Churn, because the sea, when 

 lashed into a storm, rushes up with great violence, and by 

 its wild dashing and rolling loose fallen stones over each 

 other, makes a loud rumbling noise. In the cliff on the side 

 of this gut is a section, which affords one of the most 

 marked examples of metamorphism, as well as of me- 

 chanical action. (Section 6). The basalt, which is 

 columnar, is forty feet in height (6), and beneath lies, but 

 irregularly, a broken bed of limestone (I), which, where the 

 basalt wraps over it is converted into a white granular 

 marble ; and below that are sandstones and shales (s) in a 

 broken, and disturbed condition. 



From Dunstanburgh the basalt has a continuous range 

 of six miles, two of which are along the shore southward. 

 Its position among the stratified rocks is seen again at Craster, 

 where the Muckle Carr — an island when the tide is high — 

 is partly formed of the Ebb's Nook limestone, and partly of 

 sandstone ; and beneath these the basalt dips eastward. At 

 Cullernose, near Howick, the coast section ends, and there 

 the basalt rises in great columns to the height of ninety feet ; 

 the base of which is washed by the sea. Very considerable 

 here has been the disturbance of the strata ; great masses of 

 sandstone have been displaced, and basalt, sandstones, and 

 shales are irregularly intermingled. Section (No. 7), shews 

 part of these dislocations : (b) is columnar basalt ; (s) sand- 

 stone regularly bedded ; («') sandstone displaced ; (sh) shales ; 

 (sh') shales displaced ; and at (a) the beds are nearly per- 

 pendicular. 



At this point there is a great change in the course of the 

 basalt; it makes a sudden bend and leaves the coast and 

 trends away inland, in nearly a south-west direction, across 

 the county to Tepper Moor, on the banks of the North Tyne ; 

 and perhaps this change of course may have occasioned the 

 extraordinary dislocations of the strata. 



