in the Neighbourhood of Edinburgh. 233 



ment, which, in its upper beds more particularly, passes into sandstone, often very 

 red, but sometimes of a paler reddish-brown or buff colour, and identifies itself with 

 the old red sandstone of geologists. It is now ascertained that the remains of fish 

 are enclosed in this very early formation of sandstone, and I have also observed in 

 it indications of plants. 



The termination of this deposit carries us to the dawn of the era when the car- 

 boniferous group of rocks was deposited, preparatory to which I shall make some few 

 remarks connected with the formation of the great lowland basin. 



Although I believe that the chain of the Grampians dates, at least, two of its ele- 

 vations from periods antecedent to the deposit of such strata as are known by the 

 name of the Arbroath Pavement, yet I must consider that its greatest elevation took 

 place immediately before the deposit of the carboniferous group of rocks. That this 

 convulsion was a sudden one, and attended by circumstances of great violence, is 

 evinced by the immense mass of conglomerate strata, which, in being deposited at the 

 foot of the Grampians, repose upon prior formations of the Arbroath pavement, and 

 other analogous strata. It would also appear, that the whole district intermediate to 

 the Grampians and the Tay, and extending SW. by W. to Bute, had likewise been 

 subjected to a similar process of elevation, though under an agency of far less sud- 

 denness or violence than that which had thrown up the Grampian chain. 



Along with this disturbance, a sort of nearly parallel movement appears to have 

 taken place in the elevated ridge of grauwacke schist extending in a direction of 

 ENE to WSW. from St Abb's Head to Ayrshire and Galloway, which upon this oc- 

 casion received its great elevation. 



Owing to these convulsions, the great chain of the Grampians was elevated con- 

 siderably above the level of the ocean, as may be shewn by the relative differences 

 of height which appear among the primary strata of the Scottish Highlands, and such 

 limestones of marine origin as may be found in the great valley of the Lowlands. In 

 comparing these levels, and even in allowing for any sources of error arising from 

 comparatively late disturbances of strata, no inference can possibly arise, but that at 

 the time when the coal-measures began to be formed, the Grampians must have sus- 

 tained a very considerable elevation above the level of the ocean which then subsisted. 



The same remark, though in a less degree, applies to the ridge of grauwacke 

 schist which extends from St Abb's Head to Ayrshire, and which towers greatly 

 above the carboniferous strata which repose at the foot of this lofty chain, although 

 it is, at the same time, of much less elevation than the Grampian Alps. 



It would thus appear that, intermediate to the Grampian chain, and to the chain 

 of hills, which on the south, bounds the present Lowland valley, a deep basin must 

 have subsisted. 



Within this basin the carboniferous strata of the south of Scotland were deposited. 



VOL. XIII. PART I. G g 



