Page:The Present State and Prospects of the Port Phillip District of New South Wales.djvu/25

or even a hundred degrees, down to sixty-five in a few hours. These rapid changes do not, however, seem prejudicial to health, nor have I ever known any ill consequences to result from them. It should not he forgotten, in connexion with this subject, that though these changes are sudden, and the fall of the thermometer very great, the lowest limit is seldom below sixty degrees, somewhere about summer heat in England—a temperature most conducive to health, and one in which the animal heat is easily supported and the nervous energy suffers no depression; that the heat, though great during the hot winds, is totally unaccompanied by moisture, and that it does not continue long enough to relax the frame. Practically, the reaction in the system caused by the change is felt to be most grateful. There is no doubt that the effect of these vicissitudes might be very different if they took place under different conditions: if, for instance, the fall of the thermometer, instead of being within its present limits, were from 60° to 30°, or if the great heat were of longer duration or accompanied by a moist atmosphere. The causes of these quick transitions from heat to cold may perhaps be found in the absence of high ranges of mountains, whose ridges might form a protection against the force of the wind« and amongst whose valleys the cool blasts would have become, as it were, entangled, until they had time to be tempered with the milder air of the regions in which they had just arrived, and to absorb some warmth from the heated earth. Here there is nothing to stop the south wind from the time it leaves the icebergs of the Antarctic circle until it comes against your cheek; it is,