258 AN ENQUIRY INTO THE NATURE OF [Ch. XIII. 



inclined, were originally horizontal, let it not be supposed 

 that we wish to deny that strata have experienced disloca- 

 tions, slides, or similar movements : this would be disputing 

 the evidence of our senses. Our object is to examine the 

 nature of the facts which have been adduced to prove that 

 the inclination of the rocks, on the flanks of granitic moun- 

 tains, has been produced by mechanical violence ; to bring- 

 forward objections to the validity of this evidence ; and to 

 attempt to show that the inclination is in some cases delusive, 

 and when real, as in the secondary and tertiary groups, may 

 be sometimes accounted for, by the deposition of the sedi- 

 mentary rocks on uneven surfaces. 



That the primary slates have been tilted up at various 

 angles, has been inferred from the analogy of the secondary 

 and tertiary deposits, which are supposed to have undergone 

 such elevations. 



Admitting, for the sake of argument, that this analogy is 

 correct, and that these rocks are all of aqueous origin, let us 

 enquire whether it has been indisputably established, that the 

 elevation of the sedimentary rocks has, in all cases, been 

 effected by subsequent movements ; or, if, in some instances, 

 it has arisen from other causes, endeavour to ascertain on 

 what grounds the latter are to be distinguished from the 

 former. 



It is to be presumed, that the evidence in favour of the 

 elevation of the strata is very clear and satisfactory, since it 

 has been so universally admitted. Among all the facts, how- 

 ever, brought forward in support of this opinion, none is 

 more conclusive than the occurrence of tubulites in strata, 

 placed at considerable angles to the horizon ; since it is the 

 known habit of these creatures to penetrate the ground, in a 

 perpendicular direction. " The tubulites," says Mr. Aikin *, 

 " in the clay-marl, interstratified with compact limestone, in 

 Shropshire, are very thin, and scarcely an eighth of an inch 



* Gee*. Trans., vol. i. p. 206. 



