in the Neighbourhood of Edinburgh. 251 
SECTION {X.—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 
112 
