t 207 ] 



LUl. Answer to some of the Geolosiical Queries in our last 

 Nwnler. Bij N . i .\V . Esq . ^ 



To Mr. TillocL 



Sir, — XT would have giveti me much pleasure to answer the 

 numerous questions proposed by your correspondent at page 122 

 in the last number of the Philosophical Journal, respecting several 

 interesting phaenomena noticed in the geology of the northern 

 counties : but not having visited every point in question, I must 

 be content with briefly stating my opinion on those facts which 

 have come under my own observation, referring him to Professor 

 Buckland of Oxford, and Mr. Fryer of Keswick, for an elucida- 

 tion of whatever may appear aenigmatical in the vicinity of Duf- 

 ton, &c. &:c. 



1. Tlie same formation v\hich bounds the coast of Northum- 

 berland north of the Coquet, abuts upon the eastern side of the 

 Cheviots, and passes their southern limits ; and I have every 

 reason to think the coal-mines on Tindal Fell, by which Carlisle 

 is supplied with coals, are situated in this formation ; but it is 

 the termination of the Newcastle coal-field that crops out in the 

 vicinity of Staindrop. The tract due west and north-west of the 

 Cheviots consists of gravwacke, with the old red sand-stone oc- 

 casionally reposing uj)on it. 



2. Basalt appears to owe its origin to a different cause from 

 the regularly stratified rocks vvith which it is associated, never 

 conforming with them for any considerable space. On viewing 

 a range of basaltic eiriinences stretching through a v.ide extent 

 of country, or on inspecting a strong vein filled with this sub- 

 stance, one naturally considers the former to be links of a con- 

 nected chain, and the latter a fissure of vast range : but these 

 appearances are frequently fallacious; for the tliickest beds be- 

 come thin, and soon terminate in the form cf a wedge, and the 

 veins as suddenly disappear. For instance : the two large dykes 

 explored at the surface i)y quarries, and below-ground by mines, 

 at Walbottle and Colcylhll (sec the map of Northumberland) 

 were not found a mile or two to the east, either in the workings 

 of Montague main, or East Denton collieries, or intersecting the 

 great level cut from south to north, between Bells, close by the 

 Tyjie to Kenton ; and the dyke at Walker, so well defined and 

 beautifully delineated by Mr. Hill, has not been noticed in the 

 neighbourhood. The inference is, that all theories respecting 

 tlie conlinuity of basalt are highly problematical ; and that upon 

 treating on this peculiar species of rock, one should be contented 

 to speak of it only when it can be detected in situ. 



w. Musolc shclN, gcneralfy filled with clay iron-stone, arc 



found 



