lxx:xViii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Pyrenees and of certain central portions of the Alps was originally 

 supposed to be earlier than it is now proved to have been ; and this 

 change of date must be extended, hi accordance with the theory, to 

 all those chains which belong to the System of the Pyrenees^ . These 

 and similar considerations afford no positive proof that M. de 

 Beaumont's theory is wrong — they are not now insisted on with that 

 meaning — but they do show the imperfect evidence on which it de- 

 pends, and the necessity for the greatest caution and reserve in accept- 

 ing it in any degree of generality approaching that which its author 

 would assign to it. 



There is another remark which mvist not be omitted in speaking 

 of the evidence hitherto adduced in support of this theory. M. de 

 Beaumont has brought forward many cases of parallelism, with com- 

 paratively few of well-ascertained synchronism ; but allowing the 

 cases of assumed, to be cases of real synchronism, it still remains to 

 be seen what cases there may be of synchronism without i^araUelism. 

 Parallelism without synchronism might perhaps be regarded as the 

 consequence of the recurrence of direction, but the converse is irre- 

 concileable with the fundamental principles of the theory. It is true 

 that M. de Beaumont recognizes directions as partly derived from 

 anterior movements {directions (Femjinrnt), but his mechanical ex- 

 planation of them is not in my opinion at all satisfactory!. 



Both North and South Wales and several of our coal-fields offer 

 examples of this kind. If the frequent recurrence of similar exam- 

 ples shall be hereafter established, it will necessarily, I think, be 

 subversive of the theory, except in its far more restricted application. 

 Hitherto little attention has been given to such cases vdth reference 

 to this theorj\ 



The preceding remarks apply to the evidence which has been, or 

 may hereafter be adduced for or against this theory. With respect 

 to the theory itself I may further observe, that it involves two ex- 

 treme conclusions which can never, in my opinion, be brought within 

 the limits of legitimate induction from observed phsenomena : I mean 

 that of the instantaneous elevation of mountain chains or lines of 

 elevation generally ; and that of the extension of any parallel system 

 to parts of the earth's surface between which no geological contimiity 

 whatever is traceable. 



The narrowest limits between which we can possibly, from the 

 nature of geological evidence, restrict the periods of certain move- 

 ments, are far too vride to sanction the first-mentioned conclusion as 

 expressing an essential character of each movement. The legitimate 

 induction, without its being a necessary conclusion, would be, I con- 

 ceive, that movements, greater or less in number and magnitude, had 

 taken place within certain determinate limits of time. I entertain no 

 faith in either of the extreme hypotheses — that which would reduce 

 their number to unity, or make it indefinitely great. But this is a 

 question to be discussed on independent evidence. The second of 

 the above conclusions — that which relates to the wide extension of 



* Sir C. Lyell's Principles, p. 165, Eighth Edition. f Page Ixxxii. 



