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Aiit. VI. — On Isothermal Lines ^ and the Distribution of Heat 
over the Globe. By Baron Alexander de Humboldt. 
(Continued from Vol. IV. p. 37.) 
All the ratios of temperature whicli we have hitherto fixed, 
belong to that part of the lower strata of the atmosphere which 
rests on the solid surface of the globe in the northern hemi- 
sphere. It now remains for us to discuss the temperature of the 
southern hemisphere. In few parts of natural philosophy, have 
naturalists differed so widely in opinion. From the beginning 
of the 16th century, and the first navigations round Cape Horn, 
an idea prevailed in Europe, that the southern was considerably 
colder than the northern hemisphere. Mairan and Buffbn * * 
combated this opinion by inaccurate reasonings of a theoretical 
nature. jEpinus-j- established it anew. The discoveries of 
Cook made known the vast extent of ice round the South Pole ; 
but the inequality in the temperature of the two hemispheres 
was then exaggerated. Le Gentil, and particularly Kirwan J, 
had the merit of haying first demonstrated, that the influence of 
the circumpolar ice extended much less into the temperate zone 
than was generally admitted. The less distance of the sun from 
the winter solstice, and his long continuance in the northern 
signs, act in an opposite manner || on the heat in the two hemi- 
spheres ; and as (after the theorem of Lambert) the quantity of 
light which a planet receives from the sun, increases in propor- 
tion to the true anomaly, the inequality in the temperature of 
the two hemispheres is not the effect of unequal radiation. The 
southern hemisphere receives the same quantity of light ; but 
the accumulation of heat in it is less §, on account of the emis- 
sion of the radiant heat which takes place during a long winter. 
This hemisphere being also in a great measure covered with 
* Theorie de la Terre., tom. i. p. 312 .’ — Memoires de l^Acadi 1765, p. 174. 
*j- De Distributione Calorisy 1761. 
If. Estimate., &c. p. 60 — Irish Trans, vol. viii. p. 423.— Le Gentil, Voyage 
dans CInde, vol. i. p. 73. 
tl Mairan, Mem. Acad. 1765, p. 166. — Lambert, Tyrometiie., p. 310. 
Preyost, De la Chulcur Rayonnantc., 1809, p. 329, & 367. § 280,-306. 
