MR MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 329 



mentioned in the fii'st part of this memou-, that the sand covering a workable 

 coal-seam at Joppa had been transported towards the west, carr3ang with it fi-ag- 

 ments of the coal ; — whilst fragments of the same coal were found in the lower 

 part of the boulder-clay there, considerably to the eastward. The fragments in 

 the clay had of course been washed out from the sandy bed beneath, by the 

 passage of the boulder-clay over it. 



There is therefore complete evidence of there having existed, when the stra- 

 tified rocks were broken up, a deep and extensive body of water, at the bottom of 

 which there were deposited those beds of sand and gravel, which form the lowest 

 of the superficial deposits covering the district. Nor is it dif&cult to perceive, 

 from what source, the materials of this lowest deposit were derived. That, imme- 

 diately after the elevation and rupture of the strata, their shattered remains must 

 have been washed away in enormous quantities, is evident on the slightest re- 

 flection. The simple fact, that — even in the greatest slips known in the district 

 — ^the rocks on each side of them are at one and the same level, proves that, 

 on one side at least, there must have been prodigious abrasion. One of the slips 

 at Loanhead caused the strata to sink do^vn 360 feet, — leaving of course on the 

 other side of the slip a lofty precipice of that height. One of the slips at Blink- 

 bonny must in the same way have produced a precipice of 480 feet. The great 

 SheriffhaU slip caused a precipice, which in one place would be no less than 500 

 feet, — which is as high as A^'thur Seat is above the adjoining district. It is true 

 that these precipitous fronts of shattered strata would not overhang the abyss 

 formed on one side of them, but would slope back from it. There were other cu*- 

 cumstances, however, quite sufficient to insure their speedy demolition. In the 

 first place, the dislocation of its strata, and the ponderous rubbing of their broken 

 edges against one another, when the sinking or elevation took place, would tend 

 greatly to loosen the tenacity of the materials. In the next place, we must re- 

 collect the excessive multitude of slips, by which the entire coal-field was shat- 

 tered. Indeed, so numerous are they, that there is scarcely an acre of it not ab- 

 solutely reticiilated by sMps. It is evident, therefore, that the entire district, im- 

 mediately after being so fractured and fissured, would present the spectacle of 

 numerous ridges and precipices, little calculated, from their size, form, or in- 

 ternal condition, to resist the abrading action of tides and currents. We see, 

 accordingly, that they were aU worn down, and so completely, that every trace 

 on the surface of the previous convulsions and dislocations became obliterated 

 and eifaced. The strata which had composed these submarine ridges were en- 

 tirely washed away, and converted into mere debris ; — and these again were ul- 

 timately worn down into gravel, sand, and mud. 



Such I conceive to have been the origin of the lowest superficial deposit, 

 which I have described in a former part of this memoir. It is true that this de- 

 posit has not been traced in aU parts of the district, — which it ought to have 



VOL. XIV. PART I. T t 



