258 MK MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



extent. This North Greens coal is worked or known at eight different points on 

 the west side of the basin, in a line of ten miles, — ^viz. between Joppa and Dry- 

 den ; and I have traced it to Carlips and La Mancha. It has been recognised also 

 round the whole of the south and east margin of the coal-field ; and it makes its 

 appearance on both sides of the Roman Camp ridge. 



These examples I have taken from coal-seams, because they have been more 

 diligently traced, and are more accurately known than any other kind of strata. 

 But it is not merely coal-seams, which individually extend over large tracts of 

 country. I mentioned that one of the many proofs of the identity of particular 

 coal-seams, is afforded by their roofs and pavements being the same. Over the 

 " Great Seam" there is every where a mass of red and yellow coarse sandstone, 

 between forty and fifty feet thick, which forms a continuous bed over at least 

 the greater part of the district. It may be seen in Joppa quarry — on the 

 shore at Prestonpans — in Tranent quarry — and at various places on the north 

 side of the Roman Camp ridge. Beneath the Great Seam, there is another 

 mass of sandstone, but of an entu'ely different appearance. It is generally white, 

 fine-grained, and divided with thin seams of shale, or, (to use the terms of the 

 quarrymen), " parted with black faikes." This sandstone is quarried in several 

 places for the slabs or pavement stones which can be raised from it. At the Sink 

 quarry on the Marquis of Lothian's property, there is a quarry where this white 

 sandstone, with the Great Seam, and the incumbent red sandstone, can all be 

 seen very perfectly. 



I might in like manner particulaiize various limestone strata, which may be 

 traced throughout the entire district. The limestone formerly very extensively 

 worked at Moredun and Gilmerton (lying below the North Greens coal) can be 

 traced to Loanhead, and indeed all the way to Whitfield, near Carlips. It makes 

 its appearance also on the Roman Camp ridge — dipping on the north side to- 

 wards the north — on the west side towards the west, — and on the south side to- 

 wards the south ; and it rises on the opposite side of the Tyne valley, at Middleton, 

 Crichton Dean, and other places. 



But what is true of these individual strata of coal, sandstone, and limestone, 

 is true generally speaking of aU the rocks in the district. There are very few of 

 them which may not be traced for a great many miles in all directions. 



III. The next point of inquuy, regards the respective positions of these dif- 

 ferent strata. 



In the first place, in regard to position in the basin, they seem to be aU in- 

 discriminately interspersed, except the limestone. The whole of the calcareous 

 strata are situated in the lower half of the basin ; and the thickest beds ai-e in the 

 lowest part of this half. There is no general rule of this kind characterizing the 

 strata of sandstone, shale, coal, and clay. 



