212 Mr. Hutton on the Stratiform Basalt. 



where this rock, in close contact, is totally unaltered, and, I con- 

 ceive, we should commit an error by supposing its crystalline nature, 

 where visible, always to arise from the proximity of the Whin, as in 

 some instances (in Hutton Hole Burn for example) the Limestone, 

 which is in two beds or posts,* although separated 5 feet from the Whin, 

 is first crystalline, then amorphous, and full of animal remains ; again it 

 becomes crystalline, and in the same bed soon regains its usual character. 

 The beds of Shale, also, both above and below the Whin, appear to be 

 hardened, and rendered more tenacious, so as to be used for sharpening 

 stones and slate pencils. In the Alston Moor section, the bed above 

 the Whin is designated as the Whet-stone bed, and in the time of 

 Wallis, the historian of Northumberland, the bed above the Whin at 

 Settling Stones,t near Sewing Shields, was famous for its sharping 

 stones. This pecidiarity appears to have originated the name to several 

 places in the course of the bed, as Cam Hill, near Wallington ; Cam- 

 boe, or, more probably, Cam-hoe — " Cam" being the provincial name 

 for the substance used for writing upon slates. In no situation is the 

 chemical action of the Basalt so apparent as in Teesdale ; in no other 

 situation are the Limestones and Shales acted upon so powerfully as they 

 are there, both above and below that bed ; and the impression upon my 

 mind is, that, by the depth of the valley, we there cut so far into the 

 strata as to approach near to an outlet of the volcanic matter ; not that 

 I suppose the Basalt of Belford or Holy Island to be ejected from hence 

 as from a crater, but that, perhaps, a great crack, or fissure, in the strata 

 existed ; of which the Whin Sill is the overflowing. This idea of High 

 Teesdale marking, as it were, a centre of volcanic action, is perhaps 

 corroborated by the general direction of the great Basaltic Dykes of 

 Durham and Yorkshire, they appearing to spring from hence as from a 

 focus, which had continued in activity at different periods, up to one 

 beyond even the consolidation of the oolitic series. 



As might be expected in a crystalline rock, and which is so exten- 



* See Sketch, No. 8, page 207. 



f To set or settle, in old language, means to sharpen ; so that the hardened Shale at this 

 place, from the use it was put to, seems to have given name to this ancient village. 



