506 ADDRESS DELIVERED BEFORE THE BRITISH ASSOCIATION 



We have an interesting proof of the readiness of geologists of 

 the present day to submit their views to the test of exact observa- 

 tion, in the measurements undertaken by Mr. Horner for the pur- 

 pose of approximating to the age of the sedimentary deposits. Of 

 the geological changes still in operation, none is more remarkable 

 than the formation of deltas at the mouths of great rivers, and of 

 alluvial land by their overflow. Of changes of the latter kind, 

 perhaps the most remarkable is the great alluvial deposit formed in 

 the valley of the Nile by the annual inundations of that river ; and 

 here it fortunately happens that history comes to the aid of the 

 geologist. These sedimentary deposits have accumulated round the 

 bases of monuments of known age ; and we are, therefore, at once fur- 

 nished with a chronometric scale by which the rate of their formation 

 may be measured. The first of the series of measurements under- 

 taken by Mr. Horner was made, with the co-operation of the Egyp- 

 tian Government, around the obelisk of Heliopolis, a monument 

 built, according to Lepsius, 2300 years B. c. A more extensive 

 series of researches has been since undertaken in the district of 

 Memphis ; but Mr. Horner has not yet, I believe, published the 

 results. 



The problems now to be solved in Palaeontology are clearly 

 defined in the enunciation of the problem recently proposed by the 

 French Academy of Sciences as one of its prize questions, viz., "to 

 study the laws of distribution of organic beings in the different 

 sedimentary rocks, according to the order of their superposition ; 

 to discuss the question of their appearance or disappearance, 

 whether simultaneous or successive ; and to determine the nature 

 of the relations which subsist between the existing organic king- 

 dom and its anterior states." The prize was obtained by Professor 

 Bronn, of Heidelberg ; and his memoir, of which I have only seen 

 an outline, appears to be characterized by views at once sound and 

 comprehensive. The leading result seems to be, that the genera and 

 species of plants and animals, which geology proves to have existed 

 successively on our globe, were created in succession, in adaptation 

 to the existing state of their abode, and not transmuted, or modified^ 

 as the theory of Lamark supposes, by the physical influences which 

 surrounded them. 



I must now pass, from the results of science, to the administrative 

 measures which have been adopted by this Association for its 



