ANNIVERSARY ADDRESS OF THE PRESIDENT. Hx 



the covering of sedimentary matter in the course of the enormous 

 change of position which the Alpine eocene rocks have undergone. 

 The question is one of the highest importance, because the French 

 academician contends, that all the granites erupted in the earlier pe- 

 riods of the earth's history differed from those of later date, in being 

 much more quartziferous ; and he controverts the doctrine proposed 

 by me in my * Elements of Geology,' that the difference of mineral 

 composition in the oldest rocks of this class now visible may reason- 

 ably and naturally be explained by imagining them to have originated 

 at a great depth below the surface. On the contrary, M. de Beau- 

 tnont supposes that granitic rocks charged with an excess of siliceous 

 acid were formed at the surface in the older times, and he has even 

 had the courage to present us with a diagram of Chaos, entitled 

 " Chaos primitif," representing a scene by no means rude and dis- 

 orderly, but where we behold two pyramidal mountains, from one of 

 which the ordinary volcanic lavas and more volatile substances, such 

 as sulphur, chlorine and aqueous vapour, are evolved ; while from the 

 summit of the other, granitic compounds, tin, fluor, and the more 

 refractory and less volatile materials, are discharged*. It is sug- 

 gested that the greater part of the metals which usually accompany 

 tin were concentrated in the first envelope of the globe, but after the 

 palaeozoic epoch they were withdrawn from circulation, and like the 

 primitive granites ceased to be emitted from the interior. The gases 

 and vapours, from which the more ancient metalliferous compounds 

 were sublimed, would, it is said, have been most deleterious to or- 

 ganic beings living in the air and ocean, so that their evolution in the 

 sea and atmosphere in later times was discontinued. 



For my own part, after having given the most patient considera- 

 tion to these views, I see no sufficient grounds for believing that the 

 same granitiform mixtures and metalliferous emanations may not 

 have been disengaged in equal quantity at every successive geological 

 period down to the most modern. We are taught by the activity of 

 several hundred volcanos, that there must now be lakes and seas of 

 melted matter in the interior of the earth, in every state, from one of 

 perfect fusion to one of incipient crystallization ; and as solid rock 

 must thus frequently originate in great masses, under conditions dif- 

 ferent from that of lava poured out into the atmosphere, why should 

 * Bulletin, 2nd Series, vol. iv. p. 1322. 



VOL. VI. / 



