208 Mr. Tate on Basaltic Bocks. 



westward, forming a loop which joins the line of the Roman 

 Wall at Shield-on-the-Wall, where a succession of magnifi- 

 cent cliffs of basalt commences, with deep gaps between. 

 These cliffs face the north and north-west, rising at Whin 

 Shield to one thousand feet above the sea-level ; the rock 

 having a rapid dip to the south or to the east. Along the 

 margin of the cliffs the Roman Wall has been built. In the 

 long range of ten and a half miles to Glenwhelt, there is a 

 repetition of phenomena similar to what we have observed in 

 other parts of the Basaltic Whin Sill. Metamorphism is dis- 

 tinct in several places ; and though mechanical action is less 

 general, yet at one place it is remarkable ; for between Hot- 

 bank and Rapishaw Gap, a limestone eighteen feet in thick- 

 ness is seen passing diagonally through the basalt, with a dip 

 E.S.E. 40°. Of this limestone there are several layers, all 

 metamorphosed, some hard, crystalline, and buff in colour, 

 and others dark grey, crumbling and feeling gritty like sand- 

 stone. At one of the "Nicks" westward of Cockmont, a 

 limestone, at least twelve feet in thickness, underlies the 

 basalt, the upper layers being metamorphosed and buff, and 

 the lower of a blue colour and little altered. A shale, meta- 

 morphosed, hard, and cherty, generally intervenes between 

 this limestone and the basalt, as near to Wall Town, at Hot- 

 bank, and at Rapishaw Gap. Above the basalt at Ollalee, 

 lies a good blue limestone, ten feet in thickness ; and this 

 stratum extends eastward along the slope of the hill, and is 

 seen near to House Steads and Sewing Shields ; but at the 

 latter place with a metamorphosed shale between the basalt 

 and limestone. At Bradley, however, a very different rock 

 — sandstone — overlies the basalt. 



Taking our stand on the cliff at House Steads or Borcovicus 

 we have a favourable point for observation ; and looking 

 across the country both in the line of the rise and of the dip 

 of the strata, we see on both sides of the basaltic eminence, a 

 succession of rolling hills and hollows, indicating not only 

 the outcrops of the various strata, but also the character of 

 the rocks below the surface ; for the harder sandstones and 

 limestones form the hills and rising grounds, while the 

 valleys have been scooped out of the softer shales by floods 

 and currents, and it may be by ice. The diagram 

 (Section 12) from West Stone Fell to Borcum Hill, a distance 

 of two miles, shews the succession of these beds and their 

 relative position to the basalt. Thick sandstones predominate, 



