EUCALYPTUS TREES. 135 



pulously intact, and their regular yield renaains 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 all its details. It is thus a startling 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 



