1865.] BRITISH ASSOCIATION. 34? 



period, have followed each other. Every geologist knows how, in 

 the overlying Secondary and Tertiary formations, higher and 

 higher grades of animals successively appear ; and how the relics 

 of man or his works have been detected in the youngest only of 

 the Tertiary deposits, though certainly at a period long anterior to 

 all history. We now well know that human beings coexisted 

 with quadrupeds which are extinct ; and we also know that the 

 physical configuration of the surface has undergone considerable 

 changes since such primeval men lived. This subject, opened out 

 in France by M. Boucher de Perthes, followed by some of his 

 distinguished countrymen, has in our country received much illus- 

 tration at the hands of Prestwich, Lyell, Falconer, Lubbock, 

 Evans, and others, and is now a well-established doctrine. 



But the great feature at the other end of the geological series, 

 to which I revert, is the uncontradicted fact, which has been 

 passed over by many writers, or misrepresented by others, that 

 there were enormously long periods, following that of the primeval 

 zoophytic deposits, during which the seas, though abounding in all 

 other orders of animals, were not tenanted by fishes. 



As this is a fact which the researches, during thirty years, of 

 many geologists, amidst the Lower Silurian rocks in all parts of 

 the world, have been unable to invalidate, so it teaches us, in our 

 appeal to the works of nature, that there was a beginning as well 

 as a progress of creation, and that those writers, however eminent, 

 who have announced that fishes, mollusks, and other inverte- 

 brata appeared together, have asserted that which is positively at 

 variance with the results of the researches of this century. As I 

 have in various works pointed out this great fundamental prin- 

 ciple in the origin of successive faunae, and as at my age I may 

 probably never again occupy a geological chair, I hope therefore to 

 be excused for looking back with some pride, now that I am on 

 the eastern borders of my Silurian region, to the period when, 

 thirty years ago, I dwelt on the then novel fact, never since con- 

 travened, that " the fishes of the Upper Silurian rocks appeared 

 before naturalists as the most ancient beings of their class."* 

 Enormous regions in Europe and America over which these 



* See ' Silurian System, ' p. 605. Though the work was not pub- 

 lished until 1838-39, the Silurian system and its characters were estab- 

 lished by me in 1835 (see 'Lcrodon, Edinburgh, and Dublin Philosophi- 

 cal Magazine,' 3rd series, vol. vii, p, 46, 1835). 



