242 Proceedings of the Royal Physical Society. 



of the post-tertiary epoch. That western breeze, as is well 

 known, though it brings a superabundance of moisture to 

 the districts exposed to its influence, does not bring " glacial 

 cold." The south-western counties of England and Ireland 

 are not colder than those on the eastern shore ; but, on the 

 contrary, are much warmer. 



We therefore conclude that the air lying above the inter- 

 tropical oceans, saturated though it be with moisture, when 

 conveyed to the higher latitudes, produces an effect the 

 same in kind, though less in degree, as that of the air 

 which is heated by contact with the land. The currents 

 which it forms, like those from the land, with which they 

 intermingle, flow in their northward or southward courses 

 without hindrance, and, in so far as we can judge, without 

 change. They cannot, therefore, be regarded as having pro- 

 duced the phenomena that constitute the peculiarities of the 

 glacial epoch. 



III. The third of the natural agencies, by which the 

 equatorial heat is distributed over the earth, is that of the 

 surface water of the intertropical seas. 



Those parts of the torrid zone which are covered with the 

 deep receive the same amount of solar heat as those that are 

 occupied by the land. This heat, however, is not com- 

 municated to the air that lies above them, in the same 

 manner, and in the same proportion, as that which falls on 

 the land is communicated to the air that covers it. Some of 

 the heat falling on the ocean, like that which falls on the 

 solid earth , is lost by radiation into space. There is also a 

 portion communicated to the air, to which we have already 

 referred ; but the larger portion is expended in warming the 

 water at the surface. The water thus heated becomes ex- 

 panded, and consequently lighter than that which occupies 

 the depths below ; and, like the air in contact with the in- 

 tertropical land, it flows northward and southward to the 

 poles. 



The effects produced by these warm oceanic currents are 

 familiarly known, though the laws which regulate them, 

 and the courses which they follow, have not been fully inves- 

 tigated. The Gulf-Stream, for instance, on the coast of 



