CXVl PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



under a given heat and certain pressure ; the latter very moderate, even 

 80 fathoms of water giving it, and therefore a very shght thick- 

 ness of rock. The new arrangements of the particles of mineral matter 

 from heat and pressure, under conditions for the free motion of at 

 least a portion of the component parts of rocks, and the development 

 of the forces governing the arrangement of the particles when free, 

 are daily gaining increased attention. It is no doubt an investigation 

 requiring extreme care and caution, but it is one from the skilful 

 pursuit of which the geologist may expect a considerable increase of 

 knowledge. While, however, we by no means neglect the changes 

 and modifications mineral masses may suifer from such agencies, let 

 us not forget the causes of diiference in original accumulations, and 

 those other changes and modifications which the simple infiltration of 

 new substances in solution among the particles of rocks and the re- 

 moval of others may effect during the lapse of time, not neglecting 

 the relative position of mineral masses at different periods, a consi- 

 deration of great geological importance. 



My duties as your President now terminate. I should, however, 

 be unworthy of the uniform kindness and effective co-operation ex- 

 perienced from you throughout the two years during which you 

 have honoured me with your confidence, were I to retire without 

 expressing, in all sincerity, my most unfeigned thanks for that as- 

 sistance in the performance of my duties without which your Presi- 

 dent could but ill discharge them. After an experience of thirty-two 

 years of the kind brotherly feeling which prevails among us, perhaps 

 there was little reason to expect that the indulgence and forbearance 

 enjoyed by my predecessors should not be extended to me. It never- 

 theless has been peculiarly gratifying, pressed as I have been by 

 public duties, to find my endeavours to maintain our old effectiveness 

 so indulgently viewed, and I trust that whatever may have been 

 my faults, want of anxiety for your prosperity and of an earnest 

 desire for the advance of our science will not be found among them. I 

 now resign this chair to one who has previously occupied it, whose 

 contributions to our Society have been numerous and important, and 

 whose writings have so materially advanced the science of geology, 

 feeling confident that in Sir Charles Lyell you will have a President 

 in every way fitted for the ofiice, and one who can, and will, devote 

 his time and attention to the welfare of our Society and to the means 

 it possesses of promoting the progress of that branch of knowledge 

 for the cultivation of which we are here associated. 



