MR MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



263 



the coal was entirely absent. The following sections, taken at three places where 

 the seam was worked, shew its extreme irregularity in regard to thickness and 

 composition : 



Diamond Coal-Seam. 



At Sheriffhall Pit, 



No. 21. 



At Sheriffhall Pit, No. 16. 



At BeU's Law Pit. 



Coal, . . . 

 Fire-clay,' . 

 Coal,"-' . . . 

 Fire-clay, &c. 

 Coal, . . . 



Ft. In. 

 . 1 3 

 . 1 6 



. 2 7 

 . 3 2 

 . 1 



9 6 



Coal, . . 



Fire-clay,^ 

 Coal, . . 

 Fire- clay,'* 

 Coal, . . 



Ft. In. 



. 11 

 . 22 6 

 . 5 6 

 . 6 5 

 . 1 2 



Coal, . . 

 Sandstone, 

 Shale, . . 

 Coal, . . 

 Shale, • . 

 Coal, . . 



Ft. In. 



. 84 

 . 34 

 . . 46 

 . . 3 8i 

 . 3 8 

 . 1 1 



36 6 



89 2 



' This band was, in the workings, sometimes only 6 inches thick. 



^ This band of coal, in the workings, sometimes reached a thickness of 4 feet. 



' This band was occasionally only 2 feet thick. 



* In this bed, a band of sandstone sometimes made its appearance, having a thickness of 6i feet. 



But one observation occurs here applicable to the statements made above, re- 

 garding the varying thicknesses of all the strata, coal included. These variations 

 have been inferred from examinations only at particular, and after aU, not very 

 numerous points. Now, it cannot be supposed, that the exact spots have been 

 hit on where the maximum and minimum thicknesses respectively occur. Over 

 a district about thu-teen miles square, and the strata in which, if spread out 

 horizontally, would extend greatly beyond that space, it is obvious that 100 or 

 even 1000 bore-holes must give but a partial and imperfect notion of their vary- 

 ing thicknesses, and of every thing else connected with them. It is probable, 

 therefore, that we ought to consider the variation in the thickness of the several 

 strata, to be at least double of what is shewn by the tables above referred to. 



It is not in thickness only, but in composition, that the same individual strata 

 change at different places. The best examples of this are afforded by the coal- 

 seams, they having every where been more minutely examined than the others. 



The Great Seam of coal contains generally a band of parrot ; — ^but at some 

 places, the parrot disappears from it. At Drum this parrot band is 2 feet thick, 

 — at Niddry it is 2 feet 6 inches thick ; towards its northern stretch it thins 

 off, for at Brunstain and Joppa it is only from 1 foot to 1^ foot. It thins off also 

 towards the south, and disappears altogether; at Gilmerton and Loaiihead it 

 does not exist, its place being occupied by a bed of shale. On the opposite side of 

 the basin, the Great Seam contains also a similar band of parrot ; — it occurs in it 

 in that part of the basin which is opposite to Niddry, viz. about two miles east 

 of Dalkeith, in the Duke of Buccleuch's grounds at Cowden, where it is 1 foot 

 2 inches thick. On this side of the basin, in like manner as on the other it 



