Mr. H. C. Russell, Government Astronomer for New South Wales, in his valuable pamphlet on the 'Physical Geography and Climate of New South Wales,' points out that 'if water flowed over the whole of the Australian continent, the trade wind would then blow steadily over the northern portions from the south-east, and above it the like steady return current would blow to the south-east, while the "brave west winds" and southerly would hold sway over the other half--conditions which now exist a short distance from the coast. Into this system Australia introduces an enormous disturbing element, of which the great interior plains form the most active agency in changing the directions of the wind currents. The interior, almost treeless and waterless, acts in summer like a great oven with more than tropical heating power, and becomes the great motor force on our winds, by causing an uprush, and consequent inrush on all sides, especially on the north-west, where it has power sufficient to draw the north-east trade over the equator, and into a north-west monsoon, in this way wholly obliterating the south-east trade belonging to the region, and bringing the monsoon with full force on to Australia, where, being warmed, and receiving fresh masses of heated air, it rises and forms part of the great return current from the equator to the south.' The 'hot winds' of the colonists are produced by the sinking down to the surface of the heated current of air, which in summer is continually passing overhead; and when this wind blows in force upon a clear summer's day things are not pleasant. The thermometer from time to time indicates a degree of heat which is almost incredible. In Southern Melbourne the official record gives a reading of 179 degrees in the sun, and 111 in the shade, and at the inland town of Deniliquin, the official register in the shade is 121 degrees. Man and beast and vegetation suffer on these days. The birds drop dead from the trees, the fruit is scorched and rendered unfit for market. The leaves of the English trees, such as the plane and the elm, drop in profusion, so that in early summer it will seem as if autumn had set in. The sick, especially children, are terribly affected, and the doctors attending an infant sufferer will say that nothing can be done except to pray for a change of wind. Happily, such days as these are rare. The hot blast will not often send the temperature up to more than 100 to 105 degrees, and the duration of the heated wind is limited to three days, and often it prevails during only one, sunset bringing with it a cool southern gale.