193 Prof. Heunessy on Terrestrial Climate as 



result shows the danger of under-estimating the agency of aque- 

 ous currents in connexion with any theory of the distribution 

 of land and water that may be proposed in order to explain 

 vicissitudes of terrestrial climate. 



7. In examining the consequences, resulting from the suppres- 

 sion of the Gulf-stream, on the climate of western Europe, with 

 reference to the question of glacial action at former geological 

 epochs, as has been done by Mr. Hopkins*, we need only direct 

 our attention to what actually takes place at corresponding lati- 

 tudes in the southern hemisphere. In these regions, there is not 

 only an absence of such an active calorific agent, but even an 

 abstraction of some of the heat due to them from the sunshine 

 which falls upon a portion of their oceans, which heat we have 

 seen is transferred to the northern hemisphere. Glaciers conse- 

 quently descend to the sea, not only about the latitude of 54° S., 

 as observed by Captain Cook, but even so close to the equator 

 as 48° 30' S., where they were noticed in great abundance on 

 the western coast of South America by Mr. Darwin f. He even 

 observed one instance of a glacier reaching the sea in the lati- 

 tude of 46^ 40', which corresponds to that of Napoleon Vendee, 

 in the west of France. The existence of glacial action in the 

 southern latitudes, equivalent to those of the temperate regions 

 of western Eui-ope, suggests the possibility that, by an inversion 

 of the operating causes, the southern hemisphere might have 

 enjoyed a milder climate at the same geological period that 

 glacial phsenomena were most completely developed north of the 

 equator. 



8. The results of our inquiry may be thus recapitulated : — 



(1) The physical properties of water appear upon the whole 

 more favourable than those of the land, to the accumulation, 

 retention, and distribution of solar heat throughout the matter 

 composing the external coating of the earth. 



(2) Phaenomena presented by intertropical seas at the present 

 day, confirm and illustrate this conclusion. 



(3) The distribution of land and water most favourable to a 

 general increase of terrestrial mean temperature, should, there- 

 fore, be such as would imply the existence of great intertropical 

 seas and of groups of islands evenly distributed both within the 

 tropics and in extratropical regions. 



(4) Such a distribution of land and water at former geological 

 epochs, seems to be indicated by the results of observation. 



(5) The superior mean temperature of the northern compared 

 to the southern hemisphere is probably due, not to the direct in- 



* Quarterly Journal of the Geological Society, 1852, p. 85. 

 t Voyage of ' Adventure ' and • Beagle,' iii. p. 282. 



