108 VIEWS OF NATURE. 



deeply indented by intersecting arms of the sea,) of Aus- 

 tralia, and of Africa, are respectively 34°, 46°30' and 56° 

 distant from the South Pole. The temperature of the unequal 

 extents of ocean which separate these southern extremities 

 from the icy Pole contributes essentially towards the modifica- 

 tion of the climate. The areas of the dry land of the two 

 hemispheres separated by the equator are as 3 to 1 . But this 

 deficiency of continental masses in the Southern Hemisphere is 

 greater in the temperate than in the torrid zone, the ratio being 

 in the former at 13 to 1, and in the latter as 5 to 4. This great 

 inequality in the distribution of dry land exerts a perceptible 

 influence on the strength of the ascending atmospheric current, 

 which turns towards the South Pole, and on the temperature 

 of the Southern Hemisphere generally. Some of the noblest 

 forms of tropical vegetation, as for instance tree-ferns, advance 

 south of the equator to the parallels of from 46° to 53°, whilst 

 to the north of the equator they do not occur beyond the 

 tropic of Cancer.* Tree-ferns thrive admirably well at Hobart 

 Town in Van Diemen's Land (42° 53' lat.), with a mean 

 annual temperature of 5 2°. 2 Fahr., and therefore on an iso- 

 thermal line less by 3°. 6 Fahr. than that of Toulon. Rome, 

 which is almost one degree of latitude further from the equator 

 than Hobart Town, has an annual temperature of 59°. 7 Fahr.; 

 a winter temperature of 46°. 6 Fahr., and a summer tempera- 

 ture of 86° Fahr. ; whilst in Hobart Town these three means 

 are respectively 52°, 42°. 1, and 63° Fahr. In Dusky Bay, 

 New Zealand, tree-ferns thrive in 46° 8' lat., and in the Auck- 

 land and Campbell Islands in 53° lat.f 



In the Archipelago of Tierra del Fuego, having a mean 

 winter temperature of 33° Fahr., and a mean summer tem- 

 perature of only 50° Fahr., in the same latitude as Dublin, 

 Captain King found " vegetation thriving most luxuriantly in 

 large woodv-stemmed trees of Fuchsia and Veronica;" whilst 

 this vigorous vegetation, which, especially on the western 

 coast of America (in 38° and 40° south lat.), has been so 

 picturesquely described by Charles Darwin, suddenly dis- 

 appears south of Cape Horn, on the rocks of the Southern 

 Orkney and Shetland Islands, and of the Sandwich Archipelago. 

 These islands, but scantily covered with grass, moss, and 



* See Robert Brown, Appendix to Flinders'' Voyage, pp. 575, 584; 

 and Humboldt, Be Distributione Geographica Plantarum, pp. 81 — 85. 

 t Jos. Hooker, Flora AntarcL, 1844, p. 107. 



