266 Mil MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



tion on the same scale as the horizontal section, — a circumstance too little at- 

 tended to in geological diagrams ; for otherwise, a distorted and erroneous repre- 

 sentation must be given of the whole phenomena. I have drawn these figures on 

 a large scale, so that the real depth of the basin might be easily seen, in reference 

 to its true superficial extent.* 



It will be seen from these figures what is the general shape of the basin fonned 

 by the coal strata of the district. The elevation in the middle of the figm-es, and 

 which separates the basin into separate fields, is the ridge which I have already 

 spoken of as running from the Roman Camp to Prestonpans. On the west end 

 of these lines of section the strata dip rapidly to the east, and at some places are 

 almost perpendicular ; but on the opposite side they are much less steep. At 

 several points along the Une of ridge, the individual strata mantle over, rising up 

 on one side and sloping down on the other. At other points the strata have been 

 apparently broken across, so that they crop up on both sides of the ridge, having 

 a gap or chasm between them, which in some places is thi-ee-fourths of a mile in 

 width. The fact now stated may be very distinctly seen at Ftiffet, a place about 

 three miles SE. of Dalkeith. The two ridges of limestone (the lowest of the se- 

 ries) are there distant irom each other only about 200 yards. 



Along the west side of the basin the dip of the strata is by no means regular. 

 At Joppa it is about 50°. It gets steeper towards the SW., and at Niddry and 

 Edmonstoiie they are exactly vertical. The verticaUty of the strata may be well 

 seen in a quarry near Edmonstone (West Gate), which for many years supplied 

 the yeUow-sand brought to Edinbm-gh to be sold for domestic purposes. The 

 sandstone-rock which was there worked lies between the Corby Craig coal, and 

 the Glass coal, the pei-pendicular walls of the excavated strata running in a SW. 

 direction. At Gilmerton the strata dip at an angle of about 60° ; and at Loan- 

 head at an angle of 52° ; — farther west, the dip gradually diminishes. 



On the east side of the Esk valley, the strata generally are less steep than on 

 the west side, — rising up with an angle varying from 20° to 30°. 



In the Tyne vaUey, the strata fonn a basin much flatter than the basin of the 

 Esk. On the west side, the dip is not more than 8° or 10° ; and on the east side 

 it does not exceed 5° or 6°. 



It will be seen from the annexed sections, that the coal-seams of the district 

 form as it were thi-ee series, — which may be described as the upper, the middle, 

 and the lower series. The interval between these series consist chiefly of shale 

 and sandstone, forming an aggregate thickness in the former case of 40 fathoms, 

 and in the latter of 150 fathoms. But let it not be imagined, that there are no 

 coal-seams at aU in these intervals. The tabular chart shews that there are 

 some. But they are so thin, and so far distant from each other, that the 



* The sections referred to are shewn on a smaller scale in Plate XV. at the end of this volume. 



