Page:Tracks of McKinlay and party across Australia.djvu/72

 their character, or destroyed by the supply of moisture they take up. The colonies to the south and south-east, namely, South Australia, Victoria, and New South Wales are thus in the direct route of these winds, and exposed to their full force. To these colonies they come usually as the climax to some days or weeks of preceding hot and dry weather, and they are as usually the precursors of a change of this weather—of cool southerly winds and rain.

These dry hot winds are due, then, to a region which is in general deficient in moisture and water surface, and which, at the same time, lies under a powerful sun. This usual condition is subject to occasional aggravation from unusual drought; occasionally, too, on the other hand, from an unusual rainfall this arid condition of the country is entirely, although but temporarily reversed. The result in this latter case is a rapid and wonderful change, alike in the country's aspect and in the character of its climate. Wherever there is a soil, the moist ground, fostered by the warm and now genial air, is promptly covered with vegetation; even the slopes of the sand hills sprout out with flowers; life teems forth in air, earth, and water. The hot winds are sensibly modified, and, if the rainfall is general, they are even entirely suspended. The colonies adjacent experience promptly the effect of these extremes of change that take place in the