Meteorology of Melbourne. 173 
ing of independent currents of air, the winds have a tendency 
to blow in curves, both horizontal and vertical, rather than in 
straight lines. 
When a hot wind blows out to sea, it is cooled by contact 
with the water; but, at the same time, in consequence of its 
elevated temperature, it induces rapid evaporation, and 
becomes loaded with moisture. In proportion to the fall of 
the barometer, indicating the greatness of the vacuum which 
originally caused the descent of the hot wind, and the deposi- 
tion of moisture occurring at the line of its meeting with the 
southerly wind, will be the tendency of the southerly and 
westerly winds eventually to become set in motion, in order 
to restore the equilibrium. The meeting of the cold with the 
hot wind, both comparatively loaded with moisture, will cause 
an immediate deposit in the form of clouds and rain. We 
have in fact the hot wind blown back upon us, ‘after haying 
been to sea, as it were, to bring back water. 
We are apt to complain of these hot winds as one of the 
principal inconveniences of the climate. Had we however no 
hot winds, we should probably have little or no rain. ‘The 
southerly winds would not bring it, because as they proceed 
northward they become warmer and drier, and have less and 
less tendency to deposit their moisture. Liven the winter 
rains are usually the consequence of a northerly, although we 
do not at that season call it a hot wind. 
The great redeeming feature of the Australian hot wind, is 
its low dew-point, or in other words, its dryness; but for this _ 
it would be intolerable. It is easy to conceive that with the 
thermometer at 112° and the air nearly saturated with 
moisture, profuse perspiration would be caused, but it would 
not be removed from the surface of the body, and the effect on 
the system would be nearly the same as if it were immersed 
in a scalding hot bath. It were vain to hope, and wrong to 
wish, that the hot winds of Australia should ever be abolished. 
But much may be done in the next generation to mitigate 
theirinconvenience. The cultivation of the land,and especially 
the extensive planting of trees, will have some influence. 
The leaves of trees.and shrubs act almost as wet cloths 
suspended in the air, and the cooling effect of evaporation from 
their surface is very considerable; added to which, is the 
probable cold produced by the absorption of carbon, by which 
an effect, the reverse of that produced by its oxidation or 
combustion, may be produced. The coolness of ripening 
fruits may perhaps be accounted for on this principle. The 
construction of houses, whether in adaptation to the exigencies 
