Mr. Hutton on the Stratiform Basalt. 



197 



the Limestone is imperfectly crystalline, of a loose and tender texture, 

 with here and there traces of the Encrinal Fossil. Near the centre of 

 the bed it is close grained, and compact, and is very little altered from 

 the usual characters of the Carboniferous Limestone. 



From the Roman Wall, which runs on the top of the Basalt at Sew- 

 ing Shields, where the bed is nearly 200 feet thick, a fine view of the 

 strata, both above and below it, may be seen as they successively dis- 

 play their edges croppping out beneath each other towards the north. 



No. 5. — Succession of STRATA, near Sewing Shields. 



Beyond Sewing Shields, the course of outcrop becomes more north- 

 erly, and the whole formation flattens and begins to dip a little east- 

 ward, from getting beyond the influence of the Stublick Dyke. Upon 

 Tepper Moor, the Whin forms the uppermost bed for a consider- 

 able distance, being covered only by a thin soil and scanty vegetation. 

 The Romans, in carrying their fortifications across this moor, have been 

 compelled to form their ditches in the Basalt for a great distance, which 

 must have been done with incredible labour, and they have left the 

 masses as they raised them out of the excavation, where they will long 

 remain as monuments of the skill and industry of that wonderful people. 

 These masses retain their angles sharp, and surfaces fresh, in a remark- 

 able degree, considering that they have braved the weather in an ex- 

 posed situation for so many centuries ; thus affording a lesson of caution 

 to those philosophers who reason upon the changes which are taking 

 place upon the surface of the earth from mere atmospheric causes. 



At Settling Stones, a Lead mine has been formerly worked by the 

 side of a stream which runs from near Sewing Shields towards the 

 Tyne, and which, following the dip of the strata, is, for a great part of 

 its course, upon the Whin Sill. The vein cuts the Whin, which has 

 been sunk into by a shaft 20 fathoms deep, now full of water. 



