1912-131 637 



basaltic flows, by the time they had reached this part of our 

 region, had attained a condition approaching entire solid- 

 ification. 



Again, in the vicinity of Benevenagh, delicately branching 

 pipe-amygdaloid* is of frequent occurrence, with the stems 

 normal to the bases of the layers, or nearly so, from which it is 

 evident that these fluid basalts must have lain very near their 

 origin until complete solidification supervened. Placing all these 

 facts side by side, I venture to infer that, while making full 

 allowance for outpourings from small fissures here and there over 

 the plateau, instances of which I have met with, an abundant 

 source of lava must have lain to the north of, and not very far 

 distant from, the present land. 



Another group of facts which has appeared to me worthy of 

 attention is the vast aggregate thickness of the basaltic layers 

 (900 feet or very probably more) west of the Bann, represented 

 on the published Survey maps as Lower Basalt, while immediately 

 east of the river the thickness of this member of the series — 

 lessening from East Antrim towards the west — is only about 150 

 to 200 feet. This matter is discussed in the recently issued 

 Survey Memoir,! where the conclusion is stated that the basalt 

 west of the Bann belongs to the Upper series of sheets rather than 

 to the Lower, a conclusion which involves an overlap of the series. 



The Middle Zone crops out in the Keady escarpment, where it 

 is represented by the characteristic rocks — bole, " pavement," and 

 lithomarge. The last is formed of and rests upon a thin 

 representative of the Lower Basalt, which in large part is a 

 beautifully columnar rock. 



This is associated with a black structureless basalt, with 

 inclusions of calcite in different forms, crystalline quartz, mang- 

 anese oxide, fantastically shaped congeries of Chalk flints taken 

 up from the adjoining floor, and indurated clay and flint breccias. 



*0/>. at., Vol. II., p. 187. 



f'Tlic Interbasaltic Rocks of North-east Ireland," pp. 26-28 ; 120-121. 



