46 REPORT — 18GG. 



nient way, with production of sulpliate of magnesium, with which to repeat the 

 first operation, and hydrofluoric acid, with whicli to repeat tlie second operation. 

 All the reag'ents emploj^ed for the transformation of salt into soda by this method 

 are thus continually reproduced, the only materials consumed being the salt and a 

 small quantity of fuel. The author also described some briefer methods than the 

 above of transforming salt into soda by way of the intermediate production of 

 fluoride of sodium. 



GEOLOaT. 



Address by Professor A. C. Eamsat, LL.D., F.B.S., ^c. President of the 



Section*. 



Since I last had the honour of acting as President of the Geological Section a 

 custom has crept in of opening the meetings of tlie various Sections with presiden- 

 tial addresses. I have, however, been called upon unexpectedly, and rather late in 

 the day, to occupy this chair, while I was busy -with a multitude of other avoca- 

 tions, and I have not had the time to pr.-iiare an address ; nevertheless I shall 

 endeavour to the best of my ability to say a few words upon the state of opinion 

 upon various subjects connected with physical geology, so as, possibly, to prepare 

 in some degree tlie minds of persons, who are not thoroughly conversant with all 

 branches of the science, for topics that may, perhaps, be touched upon in some of 

 the papers to be brought before us. The great question which underlies much 

 that concerns geologists is whether the economy of the world as we now see it 

 represents in kind, and partially or altogether in degree, the average economy of 

 the world as it has existed in time past, as far as it can be traced by reference to 

 rocks and their contents as they appear at the surface, or as deep beneath the sur- 

 face as we may dare to reason upon within the limits of presumed legitimate 

 inference. 



After people had thoroughly made up their minds that the world consisted, as 

 far as the outside of it is concerned, of two classes of rocks — igneous and aqueous — 

 it was for a long time the fashion to attribute most of the chief distm-bauces which 

 the crust of the earth has undergone to the intrusion of igneous masses. The 

 inclined positions of strata, the contortions of the formations in mountain-chains, 

 and the existence even of many important faults — in fact, disturbance of strata 

 generally, were apt to be referred to direct igneous action operating from below. 

 But a closer analysis of the rocks founded on careful surveys, not of a little area 

 here, and a little area there, but on surveys of kingdoms and contuients, has tended 

 to disprove these old-fashioned ideas, although you may constantly see them 

 brought up again and again in a certain class of popular works, and sometimes 

 even in memoirs by authors who ought to be better iuformed than merely to 

 repeat the notions that we find in common-place popular works on geology. 



Now, if we loolv at those British formations in which igneous rocks are most 

 generally developed, what do we find ? Go first to North Wales, to the Lower 

 Silurian strata, which are to a great extent intennixed -Rath igneous rocks. There, 

 instead of finding great masses that broke through the stratified crust of the earth 

 and tumbled the strata into confusiou, the igneous rocks consist chiefly of beds of 

 felspathic lava and ashes of great thickness interstratified among the Lower Silu- 

 rian strata, with here and there bosses of porphyry, which may sometimes repre- 

 sent, as I think, the underground nuclei of old volcinoes of Lower Silurian age ; but 

 the mountainous character of the country is due, not to the direct igneous action 

 of that period heaving up the rocks. On tlie contrary, all the rocky masses of 

 which the region consists, both igneous and aqueous, have been disturbed and 

 thrown into great sweeping imdulations formed of curved strata, thousands of feet 

 thick, by those agencies, whatever they may have been, that at a later date pro- 



* This address was very imperfectly taken down in shorthand, and the speaker has 

 since corrected it, and supplied the omissions of the reporter, to the best of his ability, 

 from memory. 



