]\I. llim\ho\di on LsothermiirLine^ SGS 
water, the pyramidal extremities of the continents have there an 
irregular climate. Summers of a very low temperature are suc- 
ceeded^ as far as 50® of south latitude, by v/inters far from ri- 
gorous. The vegetable forms also of the torrid zone, the ^ar- 
borescent ferns, and the orchideous parasites, advance towards 
38® and of S. Latitude. The small quantity of land * 
in the southern hemispheres, contributes not only to equalise the 
seasons, but also to diminish absolutely the annual temperature 
of that part of the globe. This cause is, I think, much more 
active than that of the small eccentricity of the earth's orbit. 
The continents during summer radiate more heat than the seas, 
and the ascending current which carries the air of the equinoc- 
tial and temperate zones towards the circumpolar regions, acts 
less in the southern than in the northern hemisphere. That 
cap of ice which surrounds the pole to the 71st and 68th degree 
of south latitude, advances more towards the equator, whenever 
it, meets a free sea ; that is, wherever the pyramidal extremities 
of the great continents are not opposite to it. There is reason 
to believe, that this want of dry land would produce an ef- 
fect still more sensible, if the division of the continents was as 
unequal in the equinoctial as in the temperate zones *!•. 
Theory and experience prove, that the difference of tempera- 
ture between the two hemispheres, cannot be great near the 
limit which separates them J. Le Qentil had already observed, 
that the climate of Pondicherry is not warmer than that of Ma- 
dagascar at the Bay of Antongel in 12° of S. Lat. Under the 
parallels of 20 the Isle of France has the same annual tempera- 
ture, viz. 80°.l, as Jamaica and St Domingo. The Indian 
Sea between the east coasts of Africa, the Isles of Sonde and 
New Holland, form a kind of gulf which is shut up to the north 
by Arabia and Hindostan. The isothermal lines there appear 
to go back to the South Pole ; for farther to the west in the open 
sea between Africa and the New World, the cold of the south- 
ern hemisphere already causes itself to be felt from the 22d de- 
gree, on account of its insulated mountains and particular loca- 
* The dry lands in the two hemispheres are in the ratio of 3 td'l. 
•f* The dry lands between the tropics, arc in the two hemispheres as 5 to 4, 
and without the tropics as 13 to 1. 
$ Prevost, p. 343. 
/ 
