of the North East of Ireland. 189 



ADDENDA. 



1 . Account of certain porphyrltic rocks of doubtful formation. 



2. Alluvial formations. 



J Porphyry of Sandy-brae, 



Near the centre of the basaltic area, and about seven miles north 

 north-east from Antrim, a very remarkable district occurs, in which 

 a reddish variety of clay porphyry prevails. 



This district is situated between Templepatrick on the south and 

 Kells and Connor on the north, including an area of about four 

 English miles ; proceeding from Connor in a westerly direction, you 

 first meet the porphyry formation at Carnecome, scarcely a mile 

 distant from that village, and continue uppn it for about three miles, 

 as far as the source of a small brook caPed Loonburn, which empties 

 itself into the Six mile water above Templepatrick. 



Numerous small hills are scattered over this tract ; Sandy-brae, 

 Brown Dodd, Tardree, Forthill, and Carnearny, are the names of 

 the most considerable. These are all low hummocks, exhibiting in 

 their outline a striking approach to regular segments of circles, and, 

 as Dr. -Richardson has well remarked, strongly contrasted with the 

 basaltic ridges which every where surround the porphyritic area, and 

 uniformly present an abrupt escarpment on the one side, and a gentle 

 slope on the other. The hill of Sandy-brae rises 537 feet above 

 Doagh, which, from its situation relatively to Lough Neagh, cannot 

 be estimated at less than 200 feet above the level of the sea. 



The clay porphyry of this district has a reddish brown basis, con- 

 taining imbedded in it concretions of smoky quartz, earthy and 

 glassy crystals of felspar, and olivine. Specific gravity 2,43. 



