oe R. T. McKAY. 
diminished pressure and lower temperature, as happens whenever 
a mountain range runs in a direction at right angles to the pre- 
vailing winds. (2) In the warm season the lower layers of the 
atmosphere, under the effect of solar radiation and probably other 
causes, frequently reach a state of unstable equilibrium, thus 
inducing ascensional currents. Summer thunderstorms are largely 
a result of this process. (3) Last, and doubtless most important 
of all, is the circulation of the air in cyclonic storms, viz. a radial 
inflow from all sides and an ascensional movement in the centre.” 
When rain falls slowly, accompanied by cloudy weather 
and little sunshine, there is a maximum of saturation and 
a minimum of evaporation, or in other words, rain falling 
under such conditions of cloudiness is most effective. On 
the other hand, if rain falls during continuous sunshine, 
the loss occasioned by evaporation will be greatest. 
Ip New South Wales there is an enormous loss in run-off, 
particularly in the Western Division of the State, owing to 
the duration of the wind storms. These storms, occurring 
frequently as they do, and lasting for long periods, dry out 
the soil moisture by stirring the air layers. 
If there were no vertical component in the wind, 7.e, if the air 
always moved in lines parallel to the ground surface, there would 
be no effect from it one way or the other upon evaporation. But 
wind contributes to the vapour loss of soil moisture, and the 
moisture of foliage as well, by continually bringing relatively dry 
air into contact with it directly; and the stronger the wind the 
more vigorous and efiective this action. 
Intensity of Duststorms in New South Wales.—This con- 
tinuous wind movement has resulted in denuding large 
tracts of the western plains of New South Wales of its 
surface soil, which blown away as dust, has buried fences 
and buildings that have intercepted it. Roots of trees, 
several feet below the natural surface of the ground are 
often exposed to view. Instances have occurred in New 
