TRANSACTIONS OF THE SECTIONS. 87 



GEOLOGY. 



Address ly Archibald Geikie, F.B.S., President of the Section. 



Instead of offering to the Geological Section of the British Association an 

 opening Address on some special aspect or branch of general Geologj^, I have 

 thought that it might be more interesting, and perhaps even more useful, if I were 

 to lay before jou an outline of the geology of the district in which we are uow 

 assembled. Accordingly, iu the remarks which I am now about to make, I propose 

 to sketch to j-ou the broader features of the geological structure and history of 

 Edinburgh and its neighbourhood, dwelling more especially on those parts which 

 have more than a mere local interest, as illusti-ative of the general principles of 

 our science. 



It woidd be as unnecessary as it would be out of place here to cite the long 

 array of authors who have each added to our Imowledgo of the geology of this 

 district, and many of them also, at the same time, to tlie broad fundamental truths 

 of geology. And yet it would be strange to speak here of the rocks of Edinburgh 

 Avithout even a passing tribute of gratitude to men like Hutton, Hall, Jamieson, 

 Hay Cunningham, Ilibbert, Hugh Miller, Fleming, Milne Home, and our late 

 esteemed and venerable associate, Charles Maclaren — men v,dio have made the 

 rocks of Edinburgh familiar to geologists all over the world. If, therefore, I make 

 no further allusion to these and other names, it is neither that I forget for a mo- 

 ment their claims, nor that I now bring forward any new material of my own, but 

 because I wish to be understood as dealing with facts which, thanks to the labours of 

 our predecessors, have become part of the common stock of geological knowledge. 



For the purpose of gaining as clear au idea as may be of the rock^. among which 

 Edinburgh lies, and of the way in which they are grouped together, let us imagine 

 ourselves placed on the battlements of the Castle, where, hj varying our position, 

 we may obtain a clear view of the country in every direction for many miles 

 round. To the south-east the horizon is bounded b}' a I'ange of high ground, 

 rising as a long tableland above the lowland of Midlothian. That is a portion of 

 the wide Silurian uplands of the south of Scotland, forming here the chain of 

 heights known as the Lammermuir and Jloorfoot Hills. Along most of its boun- 

 dary line, in tliis district, the Silm-ian tableland descends with tolerable rapidity 

 towards the plain, being bounded on its north-west side with a long fault, by 

 which the Carboniferous rocks are brought down against the hills. These Silurian 

 rocks are the oldest strata of the district ; and it is on their contorted and greatly 

 denuded beds that the later formations have been laid down. 



Turning now to the south, we see the chain of heights known as the Pentland 

 Hills, striking almost from the very suburbs of Edinburgh south-westward in the 

 direction of the Silurian uplands, which they eventually reach in the coimty of 

 Lanark. This Hue of hills rises along an anticlinal axis by which the broad Car- 

 boniferous tract of the Lothians is divided into two distinct portions. The Pent-^ 

 lands themselves consist, as I shall afterwards point out, chiefly of rocks of Old Red 

 Sandstone age ; but the anticlinal fold along which thej' rise is prolonged through 

 the Braid Hills, and through the Carboniferous ground by the Castle Eock of 

 Edinburgh, even as far as the opposite shores of Fife. From the Castle we can 

 readily foUow with the eye the eli'ects of this gxeat dominant fold of the rocks. To 

 the east, we mark how the strata dip away eastward fi'om the axis of movement, 

 as is shown in the escarpments of Salisbury Crag, Arthm-'s Seat, and Calton Hill, 

 while on the opposite or western side the escarpment of the wooded hill of Cors- 

 torphine, facing towards us, points out the westward dip. From the same stand- 

 point we can even detect the passage of the arch into Fife ; for the rocks about 

 Aberdour are seen dipping to the west, while eastward tliey bend over and dip 

 towards the east at Kinghorn. 



Although the structure of the district is simple when the existence and position 

 of this anticlinal axis is recognized, some little complication is introduced hy a 

 long powerful fault which flanks the axis on its south-eastern side. The efi'ect of 

 this fault is to throw out a great part of the lower division of the Carboniferous 

 formations, and to bring the Carboniferous Limestone series in some places close 



