but were these coal measures to be removed from it, that plain now laid out into the rich corn fields of Midlothian would exist as by far the profoundest valley in Scotland—a valley greatly more profound than Corrisk, or Glen Nevis, or Glencoe. Were Ben Lomond, with its three thousand two hundred feet of altitude, to be set down in the middle of this valley or basin, it would be so nearly submerged that its summit would scarce rise to the level of the Queen’s Drive. ‘We find this enormous basin, with about 170 beds of shale, clay, coal, sandstone, and ironstone, ranged layer above layer in long irregular curves, much broken by faults and shifts, but save for these breaks of greatly later date than their deposition, continuous over wide areas ; and of these 170 beds rather more than thirty consist of workable seams of coal. . . . The number of unworkable seams, varying from a few inches to about a foot and a half in thickness, amount to at least as many more. In the comparatively small section of the carboniferous strata presented in the Joppa Quarry, we find no fewer than seven coal seams, four of them unworkable and three of them wrought out. By much the larger portion of the coal in this Midlothian field seems to have been elaborated in situ, where we now find it, and it has been estimated that this coalfield alone could not have been produced in leas than six hundred thousand years.”
The workings of the several pits at Joppa followed the various seams in all directions, even to a considerable distance below the bed of the sea ; and though the shafts have been long since filled up, frequent subsidences of the soil in recent years amply confirm the extensive nature of the workings. The influx of water, whether from the sea or otherwise, seems to have been a continual source of annoyance and expense, About 1730, when the lands of Duddingston belonged to the family of Argyle, a machine, named ‘‘chains and basket,” was employed to raise the water from a great depth. When in 1745 the property changed hands, and was purchased by the Earl of Abercorn, the coal mines were let to a Mr Biggar of Woolmet, a man of considerable enterprise, who opened a ‘‘level”’ from the sea in the form of a large drain, more than three miles in extent, which he carried through the estates of Duddingston, Niddry, and part of Edmonstone, as far as Woolmetbank. This extensive ‘‘level” proved of great advantage to the proprietors of the more elevated coal works, but in the end completely ruined the collieries of Duddingston by an over-flow of water. About the year 1763, the Earl of Abercorn, in order to clear the mines of water, erected a powerful engine, where Mount Pleasant now stands, which extended its operations to a depth of fifty-two fathoms. This engine was rendered useless
