34 A NEW FLOHA OF 



The Hett Bike has a direction of E.N.E., and passes through 

 the Coal Measures, Millstone Grit, and Mountain Limestone. It 

 may possibly have its origin from the Whin Sill. It is seen in 

 Eggleston Common, and where it crosses Eggleston Burn it is 

 nearly vertical, and 33 feet wide. It is traceable eastward to 

 Hett and Quarring-ton, passing through the Crow Trees colliery 

 and dividing and charring the Eive-quarter and High Main Coal 

 Seams ; but it does not penetrate the overlying Magnesian Lime- 

 stone. As it extends eastward and approaches the surface it 

 diminishes in width, and at Crow Trees it is only 6|- feet. 



The Coclifield Bihe, from its great length, is one of the most 

 important, extending from north-west to south-east about 70 

 miles, and passing through Mountain Limestone, Millstone Grit, 

 Coal Measures, and ISTew Eed Sandstone. It varies in width 

 from 17 feet to 60 feet. At Cockfield the coal in contact with 

 it is charred, and the strata are upcast 18 feet on the south. 



]S"o basaltic dike has yet been seen among the Magnesian Lime- 

 stone strata. 



We know not the vomitaides of these augitic igneous rocks. 

 Along the whole range of the "Whin Sill no crateriform hollows 

 or cones appear : the molten matter, therefore, had probably been 

 ejected through long lines opened by deeply-seated forces acting 

 in the general direction of north to south. The vertical dikes of 

 basalt have a direction transverse to that of the Whin Sill j and 

 though, as Philips remarks, " geographically related to it," are 

 never seen in junction with it. They are too small to have been 

 the vomitaries of the Whin Sill ; and supposing they are of the 

 same age, they do not help us much to determine the period of 

 eruption. None of them, excepting the Cleveland Dike, which 

 is at the southern extremity of our district, pass through beds 

 more recent than the Coal Measures. The Whin Sill, however, 

 as Philips has shown, is anterior to the east and west veins of 

 Tynedale, for it is divided by these veins of fissure, and, as these 

 fissures have resulted from the Penine fault, the Whin Sill is 

 older than the Triassic beds. Subsequently, then, to the Carbo- 

 niferous, and prior to the Triassic era, this district was convulsed 



