MR MILNE OX THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 297 



at Fisherrow, it is about 500 fathoms below the sea-level, being a difference of 

 no less than 480 fathoms within the short interval of three miles. If the coal had 

 sloped from Cockenzie gi-adually to the west throughout these three miles, — this 

 difference of level might have been explained in another way. But it wiU be re- 

 membered, that it rises from Cockenzie to Prestonpans and Tranent, and that it 

 is from that locality, or rather from one still farther Avest, that the Great Seam 

 begins to dip into the Esk basin. I imagine, therefore, that if the Esk coal-basin 

 has not actually been created, solely and exclusively, in consequence of a hollow 

 having been formed under it, it has at all events been thereby made vastly deeper 

 and steeper than it would otherwise have been. 



(2.) The sinking would of course be greatest where the sedimentary strata 

 were nearest the volcanic outburst. This also is remarkably confirmed by the 

 fact. The centre or trough of the Esk basin runs from Fisherrow in a line 

 about SW., which is no where very distant from the course of the North Esk 

 river. Now the basin is far deeper at the north end of this line at Fisheri'ow 

 Harbour, than towards the south, as, for example, at Roslin and Lasswade ; — and 

 why ? Evidently because at the former place, it is within two miles of Arthur 

 Seat, — whilst at the latter, it is more than six miles from the Braid, Blackford, 

 and other trap hills, sku-ting the SW. limits of the coal-field. It is hardly neces- 

 sary to remark, that the same circumstance accounts for the excessive steepness, 

 or rather the verticality, of the strata at Edmonstone, Niddry, and Duddingstone, 

 — and then' compai-atively less inclination at Gilmerton, Loanhead, Dryden, and 

 other points in that du'ection. 



(3.) In considering what would be the effects of an outburst from under the 

 strata, it is proper not to confine our regards to the sinking and change of dip on 

 the west side, but also to the production of similar phenomena on the east side 

 of the basin. These would of course not take place to the same extent. Where- 

 ever the limit was, to which the subteiTanean lava reached, — beyond that limit 

 there would be no sinking ; and the strata immediately within the limit, would 

 slope down there, less rapidly than at the opposite side, in the immediate vicinity 

 of the eruption. 



Any one who has followed this reasoning, must see, that it readily explains 

 the origin of the ridge of high ground, which runs from the Frith of Forth at 

 Prestonpans to the Roman Camp by Carberry and Fuffet. That ridge forms (as 

 previously mentioned) not exactly a straight, but a curved line, the inner parts 

 of which face Arthur Seat. Moreover, the reasoning just sketched, explains the 

 fact, that alongst the inner sides of that ridge, the strata dip down less rapidly 

 than the strata on the west side of the Esk basin, — and more rapidly than the 

 strata on either side of the Tjme basin. 



(4.) It is obvious, that the sinking down of the strata, to such an extent as 

 I conceive those of the Esk basin to have sunk, — whilst the rest of the district 



VOL. XIV. PART I. p p 



