in the Neighbourhood of Edinburgh. 25 1 



SECTION IX.—REMARKS ON THE ALTERNATIONS OF BEDS OF FRESHWATER 

 AND MARINE ORIGIN, AS THEY OCCUR IN THE BURDIEHOUSE SYSTEM OF 

 STRATA. 



No geological phenomena are more striking than the very 

 miscellaneous beds which succeed each other in the Burdiehouse 

 system of strata. But similar phenomena are frequent in all the 

 coal districts of the south of Scotland. 



Some of these alternations of different deposits are explicable 

 in reference to causes which are still operating, although the cha- 

 racter of ancient geological agencies far outweighs in magnitude 

 any system of causation which is at present effecting changes on 

 the surface of our planet. 



A continued humid state of the atmosphere, for instance, 

 which is inferred to have existed during the carboniferous epoch, 

 would manifest itself in a power of disintegrating previously 

 formed rocks, to an extent of which we have little conception at 

 the present day, as well as with a proportionate degree of accelera- 

 tion. The very thick mass of sandstone which has enclosed the 

 fossil trees of Craigleith is an instance, not only of the extensive 

 disintegration of pre-existing rocks, but likewise of the very sud- 

 den drifts to which the earth, in its ancient state, has been sub- 

 jected. One of the fossil trees, 24 feet in length, was found in- 

 closed in strata dipping at little more than 10°. The tree, how- 

 ever, had an inclination of 63°, — very different from that of its 

 nearly horizontal and inclosing beds. This circumstance of in- 

 clination shews that the strata could not have been the result of 

 a slow and quiet deposition, otherwise the tree would have de- 

 cayed long before the uppermost stratum had been deposited. It 

 was doubtless conveyed to its destination by some sudden and 

 considerable drifting from high lands ; probably, by the sweeping 

 deluges of rain to which the humid atmosphere of so early a state 

 of the globe would be subject. 



Other phenomena, however, in their reference to causes which 



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