influenced by the Distribution of Land and Water. 195 



fluence of the greater proportion of land in the former, but to 

 currents which determine the transfer towards the north of a 

 portion of the solar heat absorbed south of the equator. 



9. While fully acknowledging the important influence which 

 changes in the distribution of laud and water may exercise on 

 terrestrial climate, we are not precluded from studying the action 

 of other causes, and of giving to them such weight as the evi- 

 dences in their favour may render advisable. If, from the 

 results of astronomical as well as of geological testimony, we are 

 induced to believe that the earth has been for ages slowly 

 cooling from a state of former incandescence, its climate during 

 the earlier epochs of its physical history must have been more 

 or less influenced by the heat thus passing outwards through its 

 crust. However efficient, as applied to recent phajnomena, we 

 may find the theory of geological climates that explains the va- 

 riations of the earth's superficial temperature by changes in the 

 distribution of the liquid and solid portions of its outward coat- 

 ing, it seems by itself incompetent to rationally and consistently 

 account for the very high temperature which must have pre- 

 vailed during remote epochs of the earth's history. If we reject 

 the evidence on which it has been concluded that the earth has 

 slowly cooled from a fluid incandescent state into its observed 

 condition, and admit that the earth's spheroidal shape was due 

 to gradual and even existing causes, and not to the mechanical 

 consequences of its primitive and universal fluidity, we shall 

 arrive at a conclusion which, on the supposition of the complete 

 adequacy of superficial causes to explain all changes of climate, 

 would lead to the inference that, from very remote epochs, the 

 mean temperature of the globe should be increasing instead of 

 diminishing. By rejecting the former fluid condition of the 

 earth, we are compelled to account for its oblateness in the way 

 attempted by Playfair, that is, by appealing to the influence of 

 certain superficial actions coexisting with the phjenomena of 

 geological changes. Eut I have proved * that if, from superficial 

 causes, the earth's figure became gradually more oblate, the 

 extent of polar dry land would gradually diminish, while that of 

 equatorial dry land would at the same time tend to augment. 

 Hence the very operations required to mould the earth's figure 

 into the shape now observed, would, on this theory, point to a 

 gradual increase in the efficiency of the physical conditions 

 required for an augmentation of terrestrial temperature in pro- 

 ceeding from the most remote to the most recent geological 

 epochs. But this is the very reverse of the conclusions deduced 



* Proc. Royal Irish Academy, vol. iv. p. 333 ; and Journal of the Geo- 

 logical Society of Dublin, March, 1849. 



