114 ON THE FLEXURES AND 



is possible, absolutely parallel. It is evident that, in 

 such a case, a very simple series would appear to be 

 very complicated, and this, in proportion to the 

 number of such undulations. It is further easy to 

 see, that if this undulation were vertical, or disposed 

 towards the horizon in such a manner that the paral- 

 lel portions should show a horizontal tendency, a 

 given bed, which was .truly the uppermost of the 

 series, might appear at one curvature to be the lowest, 

 or even to alternate with the others in a certain order. 

 It is easy to perceive how this fact affects the ques- 

 tion, already considered, which respects the positions 

 and alternations of strata. 



It is proper however to remark that such a decep- 

 tion can only arise in the case of one series, where 

 the different members possess, under all circumstances, 

 a conformable, or parallel position. It is impossible 

 therefore, as some careless geologists have supposed, 

 that a secondary stratum can ever appear, from this 

 cause, to lie beneath a primary one; because the un- 

 dulations of these two classes are not coincident, or 

 conformable. So far is that indeed from being pos- 

 sible, that all the considerable undulations not only 

 belong exclusively to the primary strata, but these, 

 whatever they may be, were chiefly determined long 

 before the secondary had been deposited upon them. 



The extreme curvatures and undulations which 

 have thus been considered, may, it is evident, generate 

 fractures, so that the points of contrary direction may 

 represent only the mutual meeting of two correspond- 

 ing series ; a case which has been considered in the 

 preceding chapter. Such fractures must be considered 

 as the necessary consequence of a force urged beyond 

 the power of flexibility in the strata: and that this is 

 the fact, is proved by instances where a stratum, or a 



