206 Mr. Tate on Basaltic Rocks. 



through the wood to Snab Leazes quarry. Here then we 

 find two different overflows or intrusions, one of them over- 

 lapping the other, and a rapid thinning out of the basaltic 

 pseudo-stratum, which has a wedge-shape, and in the course 

 of about five hundred yards dwindles down from about eighty 

 feet in thickness at Ratcheugh, to only three feet at Snab 

 Leazes. The Section {No. 10) illustrates this, and shews the 

 succession and relation of these rocks. 



Feet. 

 V . Columnar basalt, some parts porphyrinic, coarse in grain ; a superior) 63 



road-stone - - - - - / 



sh. Shale, highly indurated at the point of contact with the basalt ; a\ o 



porcelain jasper and Lydian stone - - - / 



I. Limestone, metamorphosed at Ratcheugh Crag - - 16 



b. Columnar basalt, 80 feet thick at Batcheugh, but at Snab Leazes \ o 



only - - - - - - j 



sh'. Indurated shale. 



The position of the basalt at Ratcheugh Crag is below the 

 Denwick Lane or Eight-Yard limestone. 



The basaltic Sill is not seen in the valley of the Aln, ex- 

 cepting at Lough House, where, though but a few feet in 

 thickness, it has been quarried as a. road-stone. It reappears, 

 however,- southward of Alnwick at Hope House and Stoney 

 Hills, at the same level as at Ratcheugh Crag ; and it ranges 

 south-westward by Greensfield, where a metamorphosed 

 shale, used for sharpening stones, lies below it, and by Rug- 

 ley, Snipe House, and Freeman Hill to Swinlees. 



From Newton-by-the-Sea to Ratcheugh Crag, the basalt 

 pursues its course among the upper beds of the calcareous 

 division of the Mountain Limestone, being either a little 

 above or a little below the Ebb's Nook limestone ; but from 

 Stoney Hills to Swinlees it is intruded among the lower beds 

 of that division, the outcrop of the basalt being two miles 

 westward of the outcrop of that limestone, and its position 

 very little above the Hobberlaw or Four-Yard limestone ; so 

 that the relative position of the Basaltic Whin Sill is here 

 one thousand feet lower in the Mountain Limestone Forma- 

 tion, than it is at Newton-by-the-Sea. 



Another long break in the continuity of the range occurs 

 across the valley of the Coquet ; but six miles south-west- 

 ward from Swinlees, the basalt is seen near to East Row on 

 the Forest Burn ; and a mile further in the same direction it 

 caps the Ebb's Nook limestone at Ward's Hill ; its relative 

 position is therefore again altered, as it is here among the 

 upper beds of the Formation. Following the course and 



