XC PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



which I have offered, long ago, that so thin a soUd shell would be 

 inconsistent with the well-ascertained amount of the precession ot 

 the equinoxes ; or, especially, without reference to the possible effect 

 of pressure, on the temperature of fusion of the different substances 

 of which the earth's crust is composed. I have long since insisted 

 on the importance of careful experiments on this subject, and I am 

 happy to avail myself of this opportunity of making to the Com- 

 mittee of the Royal Society for the disposal of the annual, grant of 

 the Government in aid of scientific researches, my acknowledgement 

 of their liberality, by which I have been enabled, in conjunction 

 with my friends ^Ir. Fairbairn and Mr. Joule, to institute the experi- 

 ments alluded to. I am now able to state, that with respect both 

 to the temperature of fusion and the conductive power of various 

 substances under great pressure, we are obtaiiring clear and determi- 

 nate results, which must form essential elements in future calcula- 

 tions or general speculations respecting the interior of our planet. 

 Wlien our experiments shall be completed, I may again, perhaps, 

 enter upon speculative researches of this nature. 



I have now. Gentlemen, discussed this subject, I trust sufficiently 

 to enable you to form your own opinions respecting the theory of 

 parallelism as now advanced by the distinguished French geologist. 

 That the phsenomena of elevation within certain districts are usually 

 connected by some geometrical law, and that such law is frequently 

 that of parallelism, I conceive to be beyond all doubt. And, moreover, 

 I think it almost equally beyond reasonable doubt, that the phsenomeua 

 thus connected may be considered as contemporaneous, not neces- 

 sarily in M. de Beaumont's absolute sense of the term, but at least 

 as regards the principal of those movements to which the pha^nomena 

 are referable. That the law of parallelism, however, especially as 

 restricted to straight lines alone, is the only law which may charac- 

 terize a system of lines of elevation, I cannot admit. The law of 

 divergency may in some cases be distinctly recognized, as in the 

 Lakes district of the North of England ; and I have already pointed 

 out to yoii* that the great circles of our author's fuseaxi are really 

 diverging and not parallel lines. But to what extent, then, are we 

 to accept M. de Beaumont's theory? So far, I reply, as we may 

 deem it founded on a legitimate induction from observed facts. 

 However we may be allowed to speculate beyond that boundary, no 

 theory not comprised within it has a right to be received, except 

 with that reserve which may leave us free ultimately to adopt or 

 reject it according to the suggestions of more enlarged experience. 



I regret that time absolutely forbids my entering into any analysis 

 of the various communications which have been made to us during 

 the past year. The subject which I have been discussing has led me 

 to analyse a considerable portion of what has been done by geological 

 observers in this country with respect to the structure of our palseo- 

 zoic districts, but I could have wished also to enter more fully into 

 details which have been recently brought forward by Prof. Sedgwick, 

 Sir R. Murchison, Mr. Sharpe and others. I have also felt desirous 

 of bringing under your particular notice the excellent paper of Sir C. 



* Page Ivi. 



