Geology of Northumberland and Durham. 29 



ton House ; crosses the river Tyne in the direction of Ryton 

 Church, and proceeds to the south-west of Greenside and 

 Leadgate, into the encrinal or mountain limestone district. 

 The rocky strata to the north of this fissure are depressed to 

 a considerable depth; but it is only at Gosforth, Killingworth, 

 and Montague main collieries, that, to use the miners' phrase, 

 the dyke has been proved. At the former of these collieries, 

 (see Section, No. 1.) its inclination or hade, and the depth to 

 which the coal-measures have been thrown down by it, have 

 been fully ascertained. 



In the second edition of Mr. Westgarth Forster's Section, 

 at page 72, is this note : — " The Great Stublick Dyke here 

 mentioned, runs in a direction nearly east and west, and may 

 be traced for a considerable distance on its line of bearing; 

 viz. from Stublick Syke westward to Cupola Bridge, where it 

 crosses the Allen Water; from thence over Whitfield Ridge to 

 the river Tyne, a little below Eals Bridge; thence to the south 

 of Hartley Bourn and Tynedale Fell collieries. It has an im- 

 mense throw down to the northward, but the precise distance 

 cannot be exactly ascertained; it must however be very con- 

 siderable, as it throws down the lower part of the Newcastle 

 coal series in the districts through which it passes. There is 

 some reason to suppose it identical with the Ninety-fathom 

 Dyke which dislocates the coal-measures near Tynemouth 

 Castle." (See page 28.) From the preceding observations it 

 appears, that previous to the year 1821, Mr. W. Forster was 

 aware that the coal seams worked at Stublick and in its vi- 

 cinity were the lower beds of the Newcastle coal-field, which 

 are not interstratified with the encrinal limestone (see Sections 

 of these mines in the First Series of the Geological Trans- 

 actions, vol. iv. page 70.), and suspected that the Stublick 

 Dyke was a continuation of the Ninety-fathom Dyke, by the 

 depression on the north side of which the Newcastle coal-field 

 was thus extended much further to the westward than it other- 

 wise would have been. 



Let us now return to the eastern extremity of this dyke on 

 the sea-coast of Northumberland. At Whitley near Culler- 

 coates, a narrow stripe of magnesian limestone detached from 

 its formation, owing to the depression occasioned by the fis- 

 sure, has long been the site of extensive quarries; but it was 

 only during the course of 1831, that, on the ground being 

 opened at a fresh place, Mr. Fryer of Whitley House ob- 

 served an irregular, though thick bed of sulphate of barytes 

 interposed between the surface-soil and the limestone. This 

 heavy spar, upon close examination, he found to consist of 

 minute brittle crystals aggregated together, of a white colour, 



