of Norlhumherland and Durham. 93 



tliese perpendicular fissures or rents being generally filled with 

 mineral matter harder than the rocks, it remains when the sur- 

 face is in part worn away, rising up like a wall. Some of the 

 dvkes are of great extent, filled with whin-stone or basalt : but 

 there is one which extends from the sea, running in a south-west 

 direction, and has thrown down the strata on one side 180 yards: 

 this is more properly a fracture of the strata than a dyke, the 

 fissure being narrow and filled with clay. This fault passes near 

 the town of Newcastle. It may deserve notice, that little if any 

 appearance of the dislocation of the strata presents itself on the 

 surface. Mr. Farey was, I believe, the first who particularly 

 called the attention of geologists to the fact of the frequent dis- 

 appearance of a whole series of strata on one side of a fault ; in 

 this instance it is truly remarkable. 



There is a very powerful whin- dyke extending across the 

 county of Northumberland from the sea in a direction westward : 

 it rises to the surface, passing about four miles north of New- 

 castle, where it is extensively quarried, as well as in many other 

 parts of its course. It is to be regretted that the information 

 Dr. Thomson received respecting it was so erroneous, as it ap- 

 pears to have prevented him from examining it at Coaly Hill, 

 where he might have seen its effects on the coal strata as it 

 passes through them. Coaly Hill is not more than about four 

 miles from the town of Newcastle: it is not a hill of basalt, but is 

 composed of the regular strata which accompany coal. The 

 whin-dvke is worked along a line of several hundred yards 

 in length for materials to lay on the roads. The width of this 

 dyke I do not accurately recolject ; but there is a cart road 

 along it where it has been worked, and a considerable space 

 left between the road and the "natural walls on each side. I 

 am informed it becomes wider in the western part of its course. 

 As it intersects the strata perpendicularly, and is worked to the 

 depth of forty or fifty feet ; the excavation forms a deep trench, 

 on the sides of which the strata of sandstone and coal may be seen. 

 I examined the coal which had been in contact with the basalt, 

 it was-tharred, or reduced to a black powder. Wishing to obtain 

 some information, from the man who was working in the dyke, 

 respecting the general effect produced by the contact of the 

 basalt with the conl, I recjuested mv frieiid the Rev. W. Tur- 

 ner, of Newcastle, who was with me, to make the inquiry in the 

 common language of tlie miners, and in such a manner as 

 might not lead him to anticipate what were my own opinions. 

 To the question: What has the whin-dyke done to the coal ? 

 The answer immediately was, 'She (meanitig the dyke) has 

 burnt the coal wherever she has touched it.' Tiiis man liad 

 worked at the quarries in the same dyke nia:iv vear«, and had 



frccjucnt 



