85 Observations on the Geology 



liferous limestone. The most valuable coal beds are called the 

 High main coal and the Low main coal, which are six feet or 

 upwards in thickness on the-Tyne ; but on the Wear, if they be 

 the same strata, their thickness is considerably less. Each stra- 

 tum ot coal grenerally, but Jiot invariably, preserves nearly the 

 same degree of thickness throughout its whole extent : but there 

 are instances here, as well as in Staffordshire and Yorkshire, of a 

 bed of coal dividing into two parts, having different degrees 

 of inclination ; or, perhaps, to speak more correctly, two beds of 

 coal in descending meet and unite. The separating strata having 

 disappeared in such instances, the bed will be much thicker than 

 before the junction. « 



The other sti ata also vary in thickness in different parts of their 

 course, but the limestone strata are observed to be more uni- 

 formly regular than the rest. The very hard strata which are 

 obliged to be sunk through by blasting, are called vvhinstone by 

 the miners ; but these are not the proper whinstone, or basalt, 

 similar to that of the dykes. There is however one bed of 

 true whinstone of vast thickness called the great whinstone (sill) 

 or bed, which is found to vary from 16 to 60 yards in tkickness. 

 This bed lies far below the principal coal strata. It is considered 

 by Mr. Forster as the same which appears on the banks of the 

 river Tees, where it forms magnificent basaltic columns, some of 

 which are not less than 40 feet in height. It extends to the 

 mountain called Cross Fell, on one side of which, I am informed, 

 there is a deep nearly circular excavation called High Cup, sur- 

 rounded by lofty basaltic columns. An intelligent gentleman 

 well skilled in nsineralogy, who has resided long in the county, 

 and paid particular attention to the subject, informed me that 

 he did not consider the great whin sill as a regular stratum, but 

 as a wedge-shaped mass of basalt, probably formed by the ex- 

 pansion of basalt from one of the great basalt dykes which intersect 

 that district. The provincial word post signifies a very firm 

 siliceous sandstone, and is differently named according to 

 its colour, as gray post, white post, &c. Hazle is also a name 

 given to some kinds of siliceous sandstone. Coal shale and the 

 clay slate of Werner are called plate. Gray beds are series of thin 

 alternating strata of siliceous sandstone and shale. It would be 

 tedious to enumerate the provincial names of all the beds ; it will 

 be sufficient to mark them by the letters S and a, to denote 

 their predominating characters, as siliceous or argillaceous 

 strata. In the rooms belonging to the Philosophicial and Li- 

 terary Society at Newcastle, sections of some of the principal 

 coal mines are kept, with series of mineral specimens of the dif- 

 ferent strata, and their provincial names affixed. It is deserving 

 notice, that in some of the coal mines there are brine springs 



containing 



