Contortions of Strata. 49 



already seen that the tabular masses are united with no form 

 and with no position and direction, and their alternation cannot 

 surprise us, how often soever it may occur ; the only thing, 

 however, which is to be attended to, is, that we do not lose 

 the thread of the connection. Should they depend on strati- 

 fication, it is easy to determine from the nature of the rock 

 whether it be of crystalline or merely mechanical formation, 

 and from other circumstances, if the strata are in their origi- 

 nal position, or if they are in an altered position, as actually 

 seems to take place occasionally in the secondary rocks under 

 certain circumstances; and we thereby obtain, not unfrequently, 

 an opportunity of accounting naturally and satisfactorily for 

 such phenomena, from the accompanying circumstances. But 

 should there, in fact, be an inversion of the order of the rocky 

 masses, as some writers at least assert to have noticed, then 

 we have a proof, if it be general, of what has been stated above, 

 that we cannot expect to find the rocky masses, in reference 

 to their mineral composition and order, in one of the specified 

 basins, precisely the same as they occur in the other ; should 

 it, however, be only partial, then the undefined order and re- 

 petition of the alternation, the wedging out of some, and the 

 change of rock of other beds, are important grounds of explana- 

 tion, which must previously be well applied ere it be resolved 

 to suppose and assume an event which harmonises but little 

 with the peaceful course of nature. This seems to be the pro- 

 per place to quote a passage from Delius,* in which that sound 

 and experienced miner remarks, " I must here remind my read- 

 ers that great care must be taken not to draw general rules 

 from one single observation respecting metalliferous rocks, be- 

 cause the contrary is often met with in other countries and 

 other metalliferous rocks. I must also caution them still more 

 to Ik; ware of framing speculative ideas, and thus, by this means, 

 restricting the operations of nature ; for, on the contrary, it is 

 necessary here to lay a foundation of varied observation, and 

 only then to form an opinion as to how it may be supposed 

 that nature may have operated.'" 



* Second edition, part 1st, page 56. 

 VOL. XXX. NO. I.IX.T— JANUAIIX 1841. D 



