10 GEOLOGY OF THE LOTHIANS. 



belong to fishes; and that the supposed Trionyx of the old red 

 sandstone of Caithness is also found to be a fish ; we may ex- 

 pect that, on more extended investigations, the nature of the 

 Stonesfield remains will appear in no way at variance with 

 their geognostical position. As it seems most accordant with 

 the rules of philosophical induction, to consider that as the 

 best founded theory which is most generally applicable, so 

 one solitary apparent exception should be the more dili- 

 gently examined ; it ought to be viewed on every side and 

 in all its details, whether it may be reconcilable with the 

 theory against which it appears to militate, rather than be 

 eagerly laid hold of, as a weapon to subvert one derived 

 from apparently legitimate generalizations. To account 

 for the non-appearance of highly organized remains in old 

 rocks, it has been asserted that causes have existed adequate 

 to effect their complete obliteration. " Mechanical pressure, 

 derangements by subterraneous movements, the action of 

 chemical affinity ," have all been summoned up to account 

 for the disappearance of animal remains which have (if we may 

 judge from evidence as strong as any attending a science, 

 the facts of which are in few instances open to experiment), 

 perhaps, never been in existence. How fickle in its actions 

 must have been that " lapidifying process'*' ! which could pre- 

 serve, even to a delicate spine, a frail shell, and be too destruc- 

 tive to allow even the fragment of a bone of a bird or mammi- 

 ferous animal to be visible in our older secondary rocks! 

 It has been told us, that as the bottom of the existing ocean 

 has not been dredged " throughout an area co-extensive with 

 that occupied by the carboniferous rocks,'" thus enabling 

 us to calculate the chances which will bring up the relic of 

 a mammifer ; so the fact of the non-appearance of these re- 

 mains ought not to be considered as a proof of their non-ex- 



