Изображения страниц
PDF
EPUB

nearly all

climate would, nevertheless, be more salubrious without them, as, during their prevalence,

persons of weakly or debilitated constitutions suffer extreme lassitude and depression. The moisture dries from the eyes, the lips become parched and cracky, the breathing short and quick, the air as it enters the mouth feels burning hot, and while sitting perfectly still the perspiration oozes from every pore in the skin. Individuals of robust constitution, however, are not thus affected: the hardy suntanned colonists freely expose themselves to the fiery blast, and, breathing the hot air full of dust and sand, toil on indifferent to everything but the demand of a parched thirst, and, in some cases, a wolfish appetite. When questioned, they reply: "Oh, the heat is no nuisance; it's the choking dust that's unbearable."

The hot winds generally commence about the middle or end of November, and re-occur at intervals throughout the summer until the end of February. They seldom have longer duration than forty-eight hours, and the number of hot wind days in summer is about fifteen, although different years vary in this respect considerably.

The scorching blasts are succeeded by a wind from the southward, and the change is inost sudden and violent. It generally occurs about four o'clock, P.M. :

a gale from the south comes rushing on, when the opposing winds battle away right furiously. They howl, shriek, tear up the dust, whiz, whirl, and beat the ground like frantic fiends; the austral invariably proves the stronger, and driving his northern antagonist backwards and upwards into the heavens, marches victoriously onwards, and in his triumphant career is hailed by man and beast as a welcome guest. Immediately the battle line of the howling blasts has passed, the air which a minute before was rendered dark as night by thick clouds of dust, earth, sand, and other light substances, carried up by the furious winds, becomes suddenly clear, and the sunlight shines out so brightly, that, for a short time, the eyes are almost blinded. When sight returns, on looking northward, a most imposing scene presents itself; a distinctly defined perpendicular wall of dust, which I can only liken to a mighty battlement, dividing the universe, extends eastward and westward to the horizon, and reaching into the heavens, beyond the limits of vision, recedes from view. The variation in temperature, from the hot northern blasts to the chilling squalls from the south, is as great as it is sudden. In November 1850, a hot wind was blowing; my thermometer in Melbourne stood at 108° in the shade, a south wind came, drove back the north, and, in rather less than five minutes, the thermometer fell to 60°, and I shook with cold from head to foot. This variation, 48°, is the greatest that I have registered on these occasions; the least is said to be 25°. Though perhaps disagreeably sudden, the change is, nevertheless, most refreshing to all animated nature. The birds of the air, and the beasts of the earth, come out from their hiding-places, and gleefully wanton in the bracing breeze; even the dogs that have buried their noses in the corners of your room, and would not go out, though you severely flogged them, now lift

up

their heads, and with a wough! wough ! joyously rush into the open air. The effect on man is equally great ; in an hour or so, all lassitude has vanished, and your wonted vigour returned.

The Australian sirocco bears some affinity to the hot winds experienced in many parts of Asia and Mexico, but whether these are caused by local circumstances, or all belong to a system of atmospheric circulation, is not authoritatively decided. There is, however, little doubt that the form, extent, altitude, and latitude, of the regions where they occur, combined with the characteristics of the soil, and the nature and extent of the vegetation, powerfully influence their production. My own impression is, that, in Australia the northern winds derive their extreme heat from passing over the low, barren, stoney desert in the interior, and that their unceasing oscillations are caused by the constant evolvement of heat from the parched earth, and the force of cooler upper currents, which rush downwards, as the heated air ascends, and in their turn again mount upwards when they become heated.

During the greater part of the year, the colonies are refreshed by cool, exhilarating breezes from the Pacific, and the summer mornings and evenings are usually deliciously cool, clear, and beautiful. On the eastern coast there are daily sea-breezes during

On the southern coast, southwest winds blow for about one hundred and forty days in the year, south-east for about fifty, south about thirty, and west about forty days. Thus sea-breezes prevail, at Melbourne and Adelaide, on an average, for about two hundred and thirty days in the year. I

summer.

« ПредыдущаяПродолжить »