160 Rev. Mr Wheweirs Address to the Geological Society, 



will thus come before the public described by the most eminent 

 naturalists, and represented in a manner worthy of the subject 

 and of the nation. I am sure that I may express the gratitude 

 of the scientific world, as weU as my own, for this enlightened 

 and judicious measure. 



I may here notice Mr Darwin's opinion, so ably exposed in 

 a paper read before us, that the change by which a variety of 

 materials thrown on the earth''s surface become vegetable 

 mould, is produced by the digestive process of the common 

 earth-worm. 



I will here also advert to Mr Fox'*s paper on the process by 

 which mineral veins have been filled up. This, he conceives, 

 might be produced by the circulation or ascension of currents 

 of heated water from the deeper parts of the original fissures. 

 The discovery of the causes of the formation and filling of 

 metallic veins, one of the earliest subjects of geological specu- 

 lation, will remain propably as a problem for its later stages, 

 when our insight into the laws of slow chemical changes is far 

 clearer than it is at the present day. 



If, from these proximate causes of change of which I have 

 spoken, we proceed to those ulterior causes by which such 

 events as these are produced, — to the subterraneous machinery 

 by which islands and continents appear and vanish in the great 

 drama of the world's physical history, — we have before us 

 questions still more obscure, but questions which we must ask 

 and answer in order to entitle ourselves to look with any hope 

 towards geological theory. Of late years an opinion has taken 

 root among us, that the dynamics of geology must invoke the 

 aid of mathematical reasoning and calculation, as the dynamics 

 of astronomy did, at the turning point of its splendid career. 

 Nor can we hesitate to accept this opinion, and to look forwards 

 to the mathematical cultivation of physical geology as one of 

 the destined stages of our progress towards truth. But we 

 must remember, that in order to pursue this path with advan- 

 tage, we have, in every instance, two steps to make, each of 

 which demands great sagacity, and may require much time 

 and labour. These two steps are, to propose the proper pro- 

 blem, and to solve it. Last year an important example of this 

 kind was brought under your notice by my predecessor. The 



