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



It was mentioned in the former part of this Memoir, that both in the " North 

 Greens" and " Great Seam," the parrot hand is thickest at and near Niddry, and 

 that it thins away, both towards the north and the south, till at length it disap- 

 pears, and its place is occupied by a bed of shale. This fact may be accounted 

 for, by supposing, that the vegetable matter was more abundantly supplied in one 

 part than in another. 



2. I have thus attempted to throw out some general views, as to the way and 

 manner in which the strata of the district were originally deposited and formed. 

 The next subject of inquiry is the history of these strata, with reference to the 

 changes and convulsions they subsequently underwent. 



This branch of the subject is no less extensive, and hardly less dark, than 

 the one just treated of. But it is perhaps possible to catch a few gleams of truth, 

 regarding the most striking and obvious of these changes. 



That these strata were deposited in positions exactly horizontal, is extremely 

 unlikely. The deposits would, near the shore of the ancient sea, slope from the 

 land at a greater or less angle. It is believed that, if the inclination to the ho- 

 rizon does not exceed 20° or 30°, sand and mud deposited on it will form regular 

 layers. Now, the strata on the south-west, south, and south-east quarters of the 

 district, slope from the hills, but they do not slope at a greater angle than 10° to 

 15° ; and, in most places, their inclination is only 5° or 6° to the horizon. The 

 amount of their slope is, therefore, no proof that they have been elevated since 

 their deposition. On the contrary, it affords some evidence that they now are, as 

 they were originally deposited. This observation applies to all that part of the 

 district which extends from the sea-shore to the north of Gladsmuir, round by 

 Pen^ne, Pentcaitland, Ormiston, Cranstone, Middleton, La Mancha, Coaley Burn, 

 and the Bents. 



But the case is widely different on the west side of the basin. There, in very 

 many places, the strata slope down at an angle of no less than 80°, and at some 

 points they are exactly vertical. This fact alone affords irrefragable evidence, 

 that, after their deposition, some prodigious force was applied, whereby these 

 strata were tilted up, and forced into a new and unnatural position. It is hardly 

 necessary to say, that the numerous hills of trap which occur on the west side of 

 the district, are quite sufficient to have caused the elevation now alluded to. 

 In the sea, there have been outbursts at Inchkeith and Inchcolm, (not to mention 

 smaller islands) : on the land, there have been outbm-sts at Lochend, Calton Hill, 

 Castle Rock, Arthur Seat, the Braid Hills, and indeed along the whole of the 

 western side of the district. 



We are thus brought to the undeniable conclusion, that, after these lime- 

 stones, coal-seams, and other sedimentary strata, were deposited and formed, 

 an epoch of subterranean convulsion arrived, which was ultimately characterized 

 by the eruption through these strata, of enormous masses of molten lava. It is 



