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Show 122 STEPPES AND DESERTS. The areas of dry land in the Northern and Southern Hemispheres are to each other in the proportion of 3 to 1. But this inferiority in extent of continental masses in the Southern Hemisphere, as compared with the Northern, belongs much more to the temperate than to the torrid zone. In the temperate zones of the Northern and Southern Hemispheres, the ratio is as 13 to 1; in the torrid zones as 5 to 4. The great inequality in the distribution of the dry land exercises a very sensible influence on the strength of the ascending aerial current which turns towards the Southern Pole, and on the temperature of the Southern Hemisphere. Some of the noblest forms of tropical vegetation, for example the tree-ferns, advance south of the Equator as far as the parallels of 46°1 and of even 53°; whereas north of the Equator they are not found beyond the tropic of Cancer. (Robert Brown, Appendix to Flinders' Voyage,pp. 575 and 584; Humboldt, de distributione geographica Plantarum, pp. 81-85.) Tree-ferns thrive extremely well at Hobart Town in Van Dicmen Island (lat. 42° 53'), where the mean annual temperature is 9° Reaumur, or 52° 2' Fahrenheit, and is therefore 1° 6' Reaumur, or 3°.6 Fahrenheit, less than that of Toulon. Rome is almost a degree of latitude farther from the Equator than Hobart Town, and has an annual temperature of 12°.3 R.1 or 59°.8 Fahr. ;-a winter temperature of 6°.5 R., or 46°.4 Fahr.,-and a summer temperature of 24° R., or 86° Fahr.; these three values being in Hobart Town 8°.91 4°.5, and 13°.8 R., or 52°.0, 42°.21 and 63° Fahr. In Dusky Bay, New Zealand, tree-ferns grow inS. lat. 46° 8', and in the Auckland and Campbell Islands, even in 53° S. lat. (Jos. Hooker, Flora Antarctica, 1844, p. 107.) In the Archipelago of Tierra del Fuego-where, in the same latitude as Dublin, the mean winter temperature is 0°.4 Reaumur (33° Fahr.), and the mean summer temperature only 8° R., or 50° Fahr.Captain King found the "vegetation thriving most luxuriantly in large woody·stemmed trees of Fuchsia and Veronica;" while this vigor of vegetation, which, e~pecially on the western coast of America in 38° and 40° of south latitude, is so picturesquely described by Charles Darwin, suddenly disappears south of Cape Horn, on tho rocks of the Southern Orkney and Shetland I slands, and of the Sandwich Archipelago. These islands, but scantily covered with grass, moss, and lichens, "Terres de Desolation," as the French na- |