610 



Dr. W. B. Carpenter on the [June 13, 



phical Equator, crossing East Africa, Arabia, and the Peninsula of India 

 nearly in that latitude north. According to Prof. Dove, the mean Summer 

 temperature in the Northern Hemisphere is 70 0, 9, while in the Southern 

 it is 59°"5 ; but, on the other hand, the mean Winter temperature of the 

 Northern Hemisphere is 48 0, 9, while that of the Southern is 53°'G. Thus 

 the mean between the Summer and Winter temperatures is 59°'9 for the 

 Northern Hemisphere, and 56°*5 for the Southern ; giving an excess of 

 about 3|° to the Northern. But the average range between the mean 

 Summer and Winter temperatures for the whole Northern Hemisphere is 

 22°, while for the Southern it is only 5°*9. The highest observed Annual 

 Bange in the whole Southern Hemisphere is only 40°, and this over a small 

 area in Patagonia which does not cover a hundredth part of its surface ; whilst 

 this range amounts to 40° over about a third part of the surface of the 

 Northern Hemisphere, and rises in the great Continental areas of Asia and 

 North America even to 80°; whilst a considerable area of Northern Asia 

 has a range of 90°, rising in some places to 100°, and at Yakutsk (which 

 lies in the centre of it) to 106°*. 



119. It may be fairly assumed, therefore, that the general difference 

 between the Thermal condition of the Northern and that of the Southern 

 Atlantic Ocean, — as regards (1) the excess of Mean temperature, and (2) 

 the greater Annual Bange, — is essentially dependent on the same agency as 

 that which produces those much larger general differences in the Conti- 

 nental Climates of the two Hemispheres, which cannot be attributed, with 

 the least semblance of probability, to a transfer of Heat from the Southern 

 to the Northern by Ocean-currents. For these last differences show them- 

 selves most remarkably in the Eastern Hemisphere, in which it is physi- 

 cally impossible that any such northward transfer of superheated surface- 

 water can take place to any but a most limited extent ; while there is strong 

 evidence, from the low bottom-temperatures found even in the Arabian 

 Gulf, that Polar Cold is imported to the North of the Equator all the way 

 from the Antarctic Ocean -j\ 



120. On more particularly comparing the course of the Isothermal lines 

 in the North and in the South Atlantic (Plate VII.), we observe that in the 

 eastern portion of the Oceanic basin, beneath the parallels of 40° North 

 and 30° South, they tend towards the Equator. This is obviously due to 

 the fact that, commencing from the coast of Portugal, a surface- flow pro- 

 ceeds southwards along the coast of Northern Africa as far as the Gulf of 

 Guinea, carrying into the Intertropical area the colder water of the Tempe- 

 rate Zone ; whilst there is a corresponding surface-flow of yet colder water 

 northwards, from the Cape of Good Hope, along the coast of South Africa, 

 as far as the Bight of Biafra. These currents are the main feeders of the 

 Equatorial current ; and although they may be partly sustained by the 

 agency of prevalent Winds, I am disposed to believe that they are essentially 



* See ' Handbook of Physical Geography,' by Keith Johnston, Jun., p. 180. 

 f See my Report for 1868, p. 187, note ; and Report for 1869, p. 473, note. 



