influenced by the Distribution of Land and Water. 189 



small area of land*. The strong presumptions furnished by the 

 fossil flora, and other evidences connected with the history of 

 earlier geological formations, in favour of the existence of nume- 

 rous islands scattered over an ocean enjoying a tropical tempera- 

 ture, should lead us to expect more of such results as are here 

 noticed, instead of feeling surprise at the discrepancies which 

 they seem to exhibit. 



6. I shall now attempt to illustrate some of the preceding 

 general views from the actual condition of the earth's surface. 

 The higher mean temperature of the northern compared to the 

 southern hemisphere is clearly proved and universally acknow- 

 ledged. This superior warmth is usually ascribed to the greater 

 amount of land in the former compared with the latter. It has 

 been apparently assumed that the surface of the dry land exercises 

 upon the whole a far more energetic influence, in tending to 

 elevate the mean temperature of the earth, than the surface of 

 the water ; and this action is generally ascribed to the superior 

 heat-absorbing power of land compared with water. Upon this 

 assumption is mainly founded the beautiful and elaborate theory 

 of geological climates, which Sir Charles Lyell first published 

 in his ' Principles of Geology.' Although Fourier had previously 

 indicated the possible influences exercised upon terrestrial tem- 

 perature by the physical conditions of the earth's outer coating, 

 he had not given his views such a definite shape as to enable 

 him to deduce any conclusions from them for the solution of 

 the great problems of terrestrial physics which have so much 

 occupied the attention of philosophical geologists. 



If the conclusions of the theory now referred to be correct, 

 it follows that predominance of land over water between the 

 tropics, where an absorbing surface would be most advantage- 

 ously circumstanced for acquiring heat, should result in pro- 

 ducing the highest possible degree of general terrestrial tempe- 

 rature. On the contrary, the earth's general climate would be 

 reduced to a maximum of coldness by a predominance of land 

 towards the polar regions, and of water towards the equator. 

 The views developed in this essay would appear to require some 

 modification in these conclusions ; and the first especially is not 

 in perfect harmony with the results to which we have been led 

 by such reasonings as I have here presented. Not only arc there 

 physical grounds for adopting a somewhat diff'erent conclusion 

 (namely, that the most favourable condition for a generally high 

 terrestrial temperature would be in a comparatively equable 

 distribution of land and water over equatorial and cxtratropical 



* Geological Society's Proceedings, June 1834, p. 94 ; and Lyell, p. 76, 

 9th edition. 



