ANNIVERSARY ADDRESS OF THE PRESIDENT. IxV 



to that of the forests which aided in the formation of the great peat 

 bogs. The land that contained these lakes and supported these ex- 

 tinct animals was in great part worn away between England and 

 Ireland, as it was between Germany and England, during the com- 

 paratively modern geological epoch, in all probability by the same 

 destructive forces. That subsidence was one cause may be legiti- 

 mately inferred, for we have abundant proof in the raised beaches 

 on our shores, that the land was subject to the action of internal 

 forces ; and masses of the post-pliocene plain of great extent and 

 thickness are found on the western shores of Britain, in the Isle of 

 Man, and in Ireland. 



The theory which it is the object of this essay to establish, is found- 

 ed, as I have already said, upon the assumption of "the existence of 

 specific centres, that is, of certain geographical points from which 

 the individuals of each species have been diffused." It is further 

 established upon the proofs, derived from various sources, of great 

 and repeated changes in the physical geography of the western and 

 north-western parts of Europe, that is, upon the existence in former 

 ages of land where there is now sea, and of sea where there is now 

 land, causing great changes of climate in these regions. The former 

 existence of a warmer climate in northern latitudes had long been 

 made manifest by the zoological and botanical evidence supplied by 

 fossil organic remains ; but the ' Principles of Geology ' of Mr. 

 Lyell, published in 1830, first taught geologists that it is not neces- 

 sary to have recourse to extraordinary causes, to account for the 

 former existence, in northern regions, of animals and plants that 

 can live only in the heat of the tropics, for the extremes of climate 

 are confined within a very limited thermometric range. He showed 

 that such a range may be produced by differences in the relative 

 proportions of sea and land, when taken in conjunction with con- 

 siderations of latitude and of the elevation of the land above the 

 sea-level, and that what we call an arctic climate, a temperate climate, 

 and a tropical climate might alternately prevail in the same latitude, 

 according as the relative proportions of sea and land, and the extent 

 and elevation of the latter, were favourable to the one condition or 

 the other. This fundamental doctrine is now embraced, I believe, by 

 the greater proportion of our geologists, perhaps universally sc, in 

 this country at least. By no one, as I have reason to know, is it 

 adopted more unreservedly than by the author of this essay ; and on 

 my remarking to him that I missed in his essay a recognition of that 

 important doctrine, which I have always been in the habit of consi- 

 dering as one of the most original and important parts of Mr. Lyell's 

 work now referred to, he replied, that believing the doctrine to be 

 so generally known and adopted, he deemed it unnecessary to refer 

 especially to it, and that he considers his essay in a great measure as 

 a contribution towards the confirmation of Mr. Lyell's climatal views. 



To Mr. Lyell we are also indebted for having several years ago called 

 the attention of geologists, not only to the effects of physical con- 

 ditions arising from changes in the earth's structure, on the existence, 

 distribution and extinction of species, but also to the great changes 



