202 Mr. Hutton on the Stratiform Basalt. 



faces towards the west as they successively rise beneath each other, 

 forming, along with the Basalt, that marked feature in the outline of 

 the country to the north and west of Belford, which must naturally 

 strike the eye of every Geologist travelling the great north road. 



The Fern Islands appear connected with the southern extremity of 

 the crescent thus indicated (as the Basalt under Holy Island Castle is 

 with the northern) ; they are portions of the Whin Sill crowning the 

 subordinate strata and rising towards the north and west ; within this 

 crescent, and of course above the Basalt, Coal, Limestone, and Sand- 

 stone are worked. 



We have thus described, in an almost unbroken line, the outcrop of 

 the Whin from Helton, in Westmoreland, to the sea coast, in the 

 northern part of Northumberland, in which extensive course, upwards 

 of an hundred miles, it is stratiform, dipping regularly with the formation 

 in which it lies, and having beds above and below it ; generally it is in 

 one bed, sometimes there are two, and, in one situation, at North 

 Heugh (as described), there are three, and it is found in contact at its 

 upper and under surfaces, with every variety of rock composing this 

 formation. 



By a reference to Smith's Geological Map of Northumberland, it will 

 be seen how nearly the line here pointed out as that of the Whin coin- 

 cides with one he defines without reference to that bed, as the outcrop 

 of a series of Limestones. 



To ascertain the exact position of this bed of Basalt, and the course 

 it holds in the series of strata, was a principal object of this examination. 

 In Forster's Section of the Strata, from Newcastle upon Tyne to 

 Cross Fell, it is placed 59 fathoms above the Melmerby Scar Limestone, 

 the most conspicuous bed of the series on the western escarpment, and 

 lOl fathoms above the Old Red Sandstone. Forster confounded the 

 Old and New Red Sandstones together, but this will be near its proper 

 position in Rundle Beck, where his section was taken, as the two are 

 there not far from the same level. The Melmerby Scar Limestone is a 

 well-defined bed, and at the mine on Murton Fell the Whin is found 

 separated from it only by a Slaty Sandstone, of 3 yards in thickness, so 



