280 ^^ MILNE ON THE MID-LOTHIAN AND EAST-LOTHIAN COAL-FIELDS. 



the superincumbent limestone occurs, and is now, or was formerly extensively 

 worked ; —as at East Salton, Tra'prain Law, Palmerston, Dunglass, Broxmouth, 

 and even as far north as North Berwick. In fact, this lowest limestone stratum, 

 with its subjacent thin seams of coal, spread over and as it were undulate through 

 the greater part of East Lothian. This at first sight is somewhat inconsistent 

 with the fact, that these identical strata crop out on the east side of what I have 

 called the Tyne basin ; but this apparent anomaly disappears, Avhen it is explain- 

 ed, that along the eastern margin of that basin there is an anticlinal Une, formed 

 by these strata dipping down again, though very gently to the east, and constitut- 

 ing, in fact, a third but very flat and extensive basin in that direction. This 

 basin reaches even to the sea on the north-east and east; — and is in various 

 parts much broken up and interrupted by eruptions of trap, of which the Garlton 

 Hills, Traprain Law, North Berwick Law, and Whitekirk Law, are the principal. 

 But, notwithstanding these interruptions and exceptions, I state it as a proposi- 

 tion generally true, that the same coal-measures which fill up the valleys of the 

 Esk and the Tyne, stretch to the sea at Aherlady, North Berwick, and Dunbar, 

 and skirt the northern flanks of the greywacke hills from the shore at Dunglass 

 as far west as La Mancha in Peeblesshire. 



Between these greywacke hills and the coal-measures, there lies an interme- 

 diate formation, which corresponds with, if it does not constitute, the old red 

 sandstone formation. It consists of red slaty sandstones, some strata of red clay, 

 and thick beds of a red conglomerate. This intermediate formation is on an 

 average not more than 150 yards in thickness. The conglomerate is uniformly 

 in the lowest part of the formation, resting immediately on the greywacke. It 

 may be seen at a great many points close to the hills, — as, for example, at King- 

 side Edge, Middleton, Blackshiels, Woodcot, Dunglass, and Thurston. The rock 

 consists of rounded pebbles, from the size of a walnut to that of a cocoa nut ; 

 they are imbedded in a clay basis, coloured and hardened Math iron, and they 

 consist chiefly of greywacke, though occasionally also of the peculiar kinds of 

 trap which occur among the Lammermuir Hills. 



It is not merely at the foot of these hills that the conglomerate occurs. It 

 may be seen also at the opposite side of the coal-field, and apparently rising up 

 from under it ; as for example at Craigmillar and at Libberton, where it is in the 

 same relative position, viz. under, and a considerable way under, all the coal and 

 lime strata. I believe the same coarse conglomerate occurs in other places, along 

 and under the western side of the coal-basin, as at the Pentland Hills, though I 

 have not myself seen it there. 



This conglomerate is (as I have said) the lowest member of the old red sand- 

 stone-formation. Its upper parts consist of red slaty sandstones, containing a 

 good deal of mica. Their smooth surface often exhibits white round spots, formed, 

 as I conceive, from a chemical change in the iron with which the stone is im- 



