Professor Ramsay's Address. 509 



the various sections with presidential addresses. I have, however, 

 been called upon unexpectedly, and rather late in the day, to occupy 

 this chair, when I was busy with a multitude of other avocations, 

 and I ha'^ e not had the time to prepare an address ; nevertheless 

 I shall en leavour 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 the minds of 

 persons, who are not thoroughly conversant with the state of opinion 

 on all branches of the science, for topics that may, perhaps, be touched 

 upon in some of the papers that may 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 surface as we may be led to reason upon by the 

 limits of presumed legitimate inference ? 



When 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 disturbances which the crust of the earth 

 exhibits to the intrusion of igneous masses. The inoKned 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 continents, 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 some- 

 times even in memoirs by authors who ought to be better informed 

 than merely to repeat the notions that we find in common-place 

 popular works on geology. Now, if we look at those British forma- 

 tions in which igneous rocks are most generally developed, what do 

 we find ? Go first to North Wales, to the Lower Silurian formations, 

 which is to a great extent intermixed with igneous rocks. There, 

 instead of finding great masses that broke through the stratified crust 

 of the earth and tumbled the strata into confusion, the igneous rocks 

 consist chiefly of beds of felspathic lava and ashes of great thickness 

 interstratified among the Lower Silurian strata, with here and there a 

 boss of porphyry, which may sometimes represent, as I think, the 

 underground nuclei of old volcanoes of Lower Silurian age ; but the 

 mountainous character of the country is due, not to the direct ig- 

 neous action of that period heaving up the rocks. On the contrary, 

 all the rocky masses of which the region consists, both igneous and 

 aqueous, have been distiu^bed and thrown into great sweeping imdu- 

 lations formed of curved strata, thousands of feet thick, by those 

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

 duced disturbance. The igneous rocks were not that cause, for they 

 have themselves been disturbed, together with the fossiliferous Lower 



