On ihe Older Stratified Rocks of Devoiishire and Cornxcall. 25 1 



This hiatus is at last, in a great measure, filled up by the 

 fossils of the older rocks of Devon and Cornwall ; and be- 

 lieving our views to be correct, we thus represent Devonshire 

 in two general sections from north to south. 



In the higher of these the carboniferous trough is seen to 

 repose at each side on the slates and calcareous sandstones of 

 the old red system. 



In the lower section the culm trough is flanked on the north 

 side only by the slaty rocks of the old red system, the granite 

 of Dartmoor having been protruded on its southern edge ; 

 while the old red system reappears again in the southern part 

 of the county, terminated by a band of micaceo-chloritic schists, 

 which are perfecdy parallel to the great disturbing axis of 

 Cornwall and Devon, and are probably altered or metamor- 

 phic strata. 



In propounding these views, we have no desire to conceal 

 the error into which we were first led by trusting too much 

 to mineral characters. We unfortunately never gave, till very 

 lately, that attention to the organic remains which is indis- 

 pensable; but having been the first to point out, that nearly 

 one half of Devonshire is the equivalent of the carboniferous 

 rocks, we have no hesitation in going a step further, guided by 

 a closer inspection of the organic remains, and by the apparent 

 fact, that this carboniferous tract passes downwards into the 

 older system. It is not the first time that we (and we believe 

 we may say every practical geologist who has examined old 

 rocks) have been deceived in attributing too high antiquity to 

 strata having an antique lithological aspect and a slaty cleavage: 

 but the day is now passed, when such features, still less the 

 mere colour or composition of rocks, can be allowed to 

 lead to any true estimate of their age. We have red sand- 

 stones and conglomerates among the slates of the Cambrian 

 system ; red and variegated sandstones abundant in the lower 

 Silurian rocks, as well as in the greatest red systems of our 

 islands, the one underlying, the other overlying, the carboni- 

 ferous deposits. 



If it be contended that the old red sandstone of Great- 

 Britain, as hitherto understood, presents a more or less uni- 

 form character in its range from the Highlands of Scot- 

 land into South Wales, we must qualify the assertion. The 

 system assumes very great mineral varieties of aspect in dif- 

 ferent regions : in some tracts (parts of Scotland and Cum- 

 berland) it is usually composed of thick, coarse conglomerates, 

 while in others such masses give way to the finest laminated 

 sandstone and shale. In the north-western districts of the 

 Highlands, so completely was an eminent geologist* misled 

 * Dr. MacCulloch. 



