252 0)1 the Mean Temperature of the 



from which formula we can easily find the latitudes which cor- 

 respond to certain temperatures. We thus find, 



As the terrestrial temperature of Cumana and Teneriffe is 

 considerably less than the points lying in the interior of South 

 America and Africa, which are under the same parallel, so must 

 the isogeothermal lines, in the ocean between Africa and Ame- 

 rica, have a considerable inflexion to the south. 



I have endeavoured to establish the terrestrial temperature at 

 the surface of the earth (or rather at a depth of 25 metres) as a 

 general law of nature, and have not, as has hitherto been done, 

 deduced it from the mean temperature of the air, with the con- 

 sideration of local circumstances. Von Buch, in the above trea- 

 tise, has endeavoured to render it probable, that the differences 

 between the terrestrial temperature and the mean of the air are 

 produced by the cooling or warming of the lower strata, by the 

 surface-water sinking downwards *. Although this may certainly 

 have some influence on the terrestrial temperature, yet many ob- 

 servations are opposed to its admission. It is not shewn, that 

 the system of subterranean waters to which the springs belong, 

 stands in any immediate connection with the atmospheric water ; 

 and rain sinks but to a small depth into the earth, particularly 

 if it is composed of rock, and is chiefly expended in the process of 

 vegetation, or evaporated, or collected into running waters. In 

 Bogoslowsk, where, for the greater part of the year, the ground 

 is covered with snow, and consequently no water can sink down ; 

 yet in mine-works the quantity of water is not greater in sum- 

 mer and autumn than in winter, and only augments in spring, 

 when the pressure of the atmospheric water is considerable, 

 from the sudden melting of the snows, and the swelling of the 

 rivers. In high latitudes, where the springs ahnost throughout 



* Vide Remarks on Temperature of Springs, by Von Buch, p, ICC, vol. vi. 

 of the Edin, New Pliil. Journ. 



