222 Analyses of Books. [Sept. 



whatever it was, which has dislocated the beds of the coal form- 

 ation. Although workings of coal have, in a few instances, 

 been actually driven a little way under the cover of the magne- 

 sian limestone, yet all attempts to pierce through these beds in 

 their dip, and su to reach the coal, have been fruitless. Large 

 cavities in this limestone are filled by a breccia, the cement of 

 which is a soft, marly, magnesian carbonate of lime ; and where 

 these occur in the cliffs on the coast, the action of the water 

 upon them produces first large caverns, and then extensive slips 

 and ruins, as may be observed at Hartlepool, Marsden, and 

 Monk- Wearmouth . 



The rock which appears the next in succession to the magne- 

 sian limestone is the coal formation. It occupies the face of 

 the country west of the magnesian limestone, forms the coast 

 from the mouth of the Tyne to that of the Coquet, proceeds up 

 along the south bank of this river for five or six miles, whence 

 it stretches to the Tyne about 10 miles above Newcastle, and 

 terminates on the eastern extremity of Weardale and Teesdale 

 forests. It rests, as usual, on a bed of very coarse sandstone, 

 called the millstone-grit. The greatest depth to which any pit 

 has been sunk in the coal measures is about 200 fathoms, and 

 the entire thickness of the formation, as deduced from a succes- 

 sion of sections, appears not much to exceed 270 fathoms. Of 

 the coal there are two varieties, namely, the common slate coal,, 

 and candle coal, called, in Northumberland, splint, or parrot 

 coal. The other strata that compose the coal measures are shales 

 (slaty clay) and micaceous sandstone of different degrees of fine- 

 ness. The shales are either simply carbonaceous, or bituminous, 

 and many of them when decomposed form a refractoiy clay 

 proper for fire-bricks and potters' saggars. The grindstone sill 

 is a fine grained sandstone, loosely aggregated, and forms the 

 material of the celebrated Newcastle grindstones; the softer 

 parts afford good filtering stones, and the yellow sand, which 

 often constitutes the upper part of the bed, is sold to casters in 

 iron, &c. as an ingredient in the composition of their moulds. 



The organic remains, both vegetable and testaceous, are 

 described by Mr. W. ; and a particular account is given of the 

 principal basaltic dykes by which the coal field is in various parts 

 intersected. 



The principal supply of the metropolis, of the eastern and part 

 of the southern counties of England is derived from this coal 

 field; hence the annual export from Newcastle, Sunderland, 

 Hartley, and Blyth, amounts to about 2,000,000 London chal- 

 drons-. 



The millstone grit, which has been already mentioned as 

 supporting the coal formation, rests upon the lead mine measures 

 which occupy nearly the whole of the counties of Durham and 

 Northumberland to the north and west of the coal formation, 

 with the exception of the Cheviot Hills. The strata rise about 



