470 BOTANICAL GEOGRAPHY. 



variable winds, which are dependent upon the monsoons of the adjacent 

 oceans, but are not the same in the different latitudes. At Port Jackson 

 and Port Macquarie (32 S. lat.) equatorial winds prevail in the summer and 

 polar currents in the winter ; in Port Philip (south-eastern extremity of the 

 continent) equatorial currents in the winter, and polar currents in the sum- 

 mer ; in Van Diemen's Land the equatorial winds predominate throughout the 

 whole year (p. 168). The amount of rain is far more considerable on the 

 coast than we should expect : on the average it amounts to 48" 6 in New 

 South Wales, and to 41" 3 in Van Diemen's Land (p. 192). The temperature 

 is far more uniform than in corresponding latitudes of the northern hemi- 

 sphere, as is shown by the following table (p. 229). 



Woolnorth in 



Port Port Port Van Diemen's 



Macquarie. Jackson. Philip. Laud. 



Mean temperature +20 c. -f!92c. +16 3 c. -f!4lc. 



+ 23 9 " +23 2" +20 8" +16 



Mean winter tern- ) +16 o r +15 i>/ +11 9" +12 3 



. perature 5 



Maximum of summer +31 3"* 4-27 8"f + 32 5f +204J 



winter + 8 2* + 7 4 + 27f + 8J 



The influence of the geological conditions upon the vegetation and the cul- 

 tivation of the soil is exceedingly variable, according to Strzelecki, as shown 

 by a comparison of New South Wales with Van Diemen's Land. In New 

 South Wales, granite, sandstone, and conglomerate predominate ; limestone 

 is confined to but few localities ; in Van Diemen's Land, porphyry, greenstone, 

 basalt, and trachyte predominate ; limestone is also common (p. 360). In 

 the former, the silica existing in the soil favours the nocturnal diminution 

 of temperature, and would act still more prejudicially if the vegetation, which 

 is more dense, did not frequently give rise to the formation of clouds (p. 219). 

 But the small quantity of soluble constituents in the soil renders it only 

 adapted for indigenous plants, as for pasture-land, but not for agriculture. 



The botanical letters from New Holland, by Leichardt 

 (Lond. Jonrn. of Bot., 1845, pp. 278-291), whose great 

 voyage of discovery through the interior of the continent, 

 which has never been surpassed in its results, was de- 

 scribed without a view to publication, excite the most 

 sanguine hope that the botanical characteristics of 

 Australia, taken up by such talent for observation, and 

 described in an equally successful manner, will, at some 



* The warmest month is November ; the coldest, August. 

 f The warmest month is November ; the coldest, July. 

 | The warmest month is January ; the coldest, August. 



