Mr. Hutton on the Stratiform Basalt. 2 13 



sively developed, a considerable variety is exhibited in the Whin itself. 

 The character it bears almost throughout is that of the common green- 

 ish-grey compound of Felspar and Hornblende ; occasionally these con- 

 stituents crystallize separately, and form a beautiful rock, as at Tyne 

 Head Force, in Gilderdale Burn, and on the side of the new road above 

 High Force, in Teesdale ; here the rock exhibits in small patches, an 

 aspect sometimes exceedingly like the Sienite of Carrick Fell, and, like 

 it, appears to contain Hypersthene. 



In Raven Beck and Croglin Water, where the surfaces of the beds of 

 Basalt come in contact with the interposed Sandstone, before mention- 

 ed,* the Basalt is dark coloured, and of exceedingly fine grain, breaking 

 with a conchoidal fracture, and having very small patches of Iron Py- 

 rytes in it ; this is a character also, which does not extend far into the 

 mass, as at the depth of 6 or 8 inches the rock regains its usual as- 

 pect. 



Sometime it is porphyritic, having distinct crytsals of Felspar em- 

 bedded in it. At Copping Crag, on the north bank of the Wansbeck,t 

 near Whelpington, a remarkable variety occurs ; the general character 

 of the rock is altered, it is distinctly granular, of a lighter colour, arising 

 from a light green mineral, apparently Felspar, disseminated in it, 

 and it effervesces with acids ; suddenly in spots it becomes perfectly 

 white, and specimens may be procured one half green and the other 

 white. 



A very curious variety of this rock occurs on the south bank of 

 Embleton Mill Burn, which appears composed of crystalline Felspar, 

 without Hornblende, and is of a red colour, apparently from the pre- 

 sence of Oxyde of Iron. 



Having now detailed the observations I made upon the Whin Sill as 

 briefly as the great extent of the subject would admit, and stated the 

 views I have been led to entertain from the survey ; I have only further 

 to return my grateful acknowledgments to Mr. H. L. Pattjnson, of 

 Low Byer, near Alston, whose kindness and readiness to assist all who 

 visit that place are so well known, and to the Rev. John Hodgson, of 



* See page 193. f See page 199. 



