164 FOREST CULTURE AND 
of sea-breezes renders the more littoral tracts of West 
and North Australia almost free. But in the econo- 
my of nature the trees, beyond affording shade and 
shelter, and retaining humidity to the soil, serve 
other great purposes. Trees, ever active in sending 
their roots to the depths, draw unceasingly from below 
the surface-strata those mineral elements of vegetable 
nutrition on which the life of plants absolutely de- 
pends, and which, with every dropping leaf, is left as 
a storage of aliment for the subsequent vegetation. 
How much lasting good could not be effected, then, 
by mere scattering of seeds of our drought-resisting 
Acacias, and Eucalypts, and Casuarinas, at the termi- 
nation of the hot season along any water-course, or 
even along the crevices of rocks, or over bare sands 
or hard clays, after refreshing showers? Even the 
rugged escarpments of the desolate ranges of Tunis, 
Algiers, and Morocco might become wooded ; even 
the Sahara itself, if it could not be conquered and 
rendered habitable, might have the extent of its oases 
vastly augmented ; fertility might be secured again 
to the Holy Land, and rain to the Asiatic plateau, or 
the desert of Atacama, or timber and fuel be furnish- 
ed to Natal and La Plata. An experiment instituted 
on a bare ridge near our metropolis demonstrates 
what may be done. 
Not Australia alone, but some other countries, have 
judiciously taken advantage of the facilities afforded 
by Australian tree-vegetation for raising woods —an 
object which throughout the interior might be ini- 
tiated by rendering this an additional purpose of the 
expeditions to be maintained in the field for territo- 
rial and physiographical exploration ; and more, it 
