EUCALYPTUS TREES. 99 
pulously intact, and their regular yield remains secur- 
ed from year to year and from century to century. 
He would rest satisfied if only the trifling revenue 
of the forests could be applied by him and his neigh- 
bors to an inexpensive restoration of the woods con- 
sumed. He would delight in seeing the leading for- 
eign timber trees disseminated with our own Red 
Gum-tree, Red Cedars, Yarrahs or Blackwoods, not 
by hundreds but in time to come by millions, well 
aware that the next generations may either censure 
reproachfully the shortcomings of their ancestors, or 
may point gratefully to the results of an earnest and 
well-sustained foresight of future wants. As a first 
step, at least in each district a few square miles should 
be secured for subsequent forest nurseries in the best 
localities, commanding irrigation by gravitation, and 
ready access also, before it is too late, and all such 
spots are permanently alienated from the Crown. 
Physical science must yet largely be called to our 
experimental aid before we can dispel the many crude 
notions in reference to the effect of forest vegetation 
on climate in allits details. It is thusastartling fact, 
as far as experiments under my guidance hitherto 
could elucidate the subject, that on a sunny day 
the leaves of our common Eucalypts and Casuarinas 
exhale a quantity of water several times, or even 
many times, larger than those of the ordinary or 
South European Elm, English Oak, or Black Poplar ; 
while from the foliage of our native Silver Wattle 
only half, or even less than half, the quantity of 
water is evaporated than from the Poplar or Oak. 
This degree of exhalation, so different in various 
trees, depends on the number, position, and size of 
