96 SOME CAUSES OF THE DECAY OF AUSTRALIAN FORESTS, 
to be beneficial in removing malaria from marshy places, is not so 
much on account of any essential oil which they may give off, as 
to the fact that, while they probably evaporate as much or more 
water from their leaves, they, from the vertical or pendant position 
of the leaves, unlike other trees, cast but little shade. The ground 
underneath a gum-tree is never damp and moist in dry weather as 
it is under ordinary European and other shade-giving trees, so that 
an area planted with such trees is exposed to the combined drying 
influence of the sun and to the ae iota of water by the roots 
and subsequent evaporation from the leaves. 
t been suggested that the saaniae bluish haze Senay in _ 
A ealian bush is also due to this essential oil; but from 
experiment made in conjunction with Mr. Russell, the spectr casas 
gave no indication of its presence in the atmosphere. The matter, 
however, is worthy of further investigation. 
