ANNIVERSARY ADDRESS OF THE PRESIDENT. XXXV 



ment, than the strike of the moderately incUned beds, and would be 

 the phsenomena which might frequently be most depended on for 

 giving the characteristic directions in such cases as those we are 

 speaking of, provided the longitudinal could be distinguished from 

 the transverse faults. 



If the beds, affected as we have here supposed by two successive 

 movements, be in the immediate neighbourhood of other beds 

 affected only by the last movement, and therefore affording a 

 measure of its magnitude and giving its characteristic direction, 

 we can easily eliminate the effects of that movement on the beds 

 affected by both movements. But in regions where we have no such 

 means of analysing the resulting effects, it must be impossible to 

 assign with any accuracy their characteristic directions to the earlier 

 movements. The great disturbance, for example, which broke up 

 the coal-measures in this country, must doubtless have extended far 

 beyond the limits in which we now find coal and the beds associated 

 with it, and must have materially modified the effects of former 

 movements. 



All theories of elevation, in their application to the older forma- 

 tions, must be in like manner affected by the difficulty of analysing 

 the effects of successive movements which have disturbed those 

 formations, but they may be affected in very different degrees. In 

 the case before us, we have to consider the importance of this diffi- 

 culty in a theoiy, which, even in its present professedly imperfect 

 development, requires the determination of the angular positions of 

 the characteristic lines of elevation, as we shall see in the sequel, 

 with a close approximation to accuracy. 



I have here discussed this source of indeterminateness in our 

 author's theory as lying in the difficulty of deducing from existing 

 lines of elevation the characteristic directions of the earlier move- 

 ments which affected the older rocks at certain assumed successive 

 epochs. We may further inquire what is the nature of the evidence 

 in support of the assumption that each group of lines characterized 

 by a particular direction is really to be referred to one particular 

 epoch. Now if you follow carefully the description given by M. 

 de Beaumont, of the systems which he has particularized, you will 

 find instances in which this evidence is independent and satisfac- 

 tory — those in which a movement has affected any formation with- 

 out affecting the superincumbent beds. But in other instances, 

 you will observe that lines of elevation are referred to a certain epoch 

 merely because they are parallel to other lines belonging to that 

 epoch, in another and sometimes distant locality. It must not be 

 hence inferred that any confusion on these points exists in the mind 

 of the distinguished author of this theory. He doubtless considers 

 that the number of the first class of the above-mentioned cases — that 

 in which the evidence of the contemporaneity of parallel lines is inde- 

 pendent and satisfactory — is sufficient to justify the induction that 

 the mere parallelism of the lines, in the second class of the above 

 cases, is sufficient proof of the contemporaneity of their origin. It 

 is essential, however, for those who would make a critical examina- 



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