EXTREME SOLAR HEAT.
The fluctuation in the sun’s direct heating power amounts to 1/15th, which is too considerable a fraction of the whole intensity not to aggravate in a serious degree the sufferings of those who are exposed to it in thirsty deserts without shelter. The amount of these sufferings, in the interior of Australia for instance, are of the most frightful kind, and would seem far to exceed what have ever been undergone by travellers in the northern deserts of Africa. Thus Captain Sturt, in his account of his Australian exploration, says: “The ground was almost a molten surface; and if a match accidentally fell upon it, it immediately ignited.” Sir John Herschel has observed the temperature of the surface soil in South Africa as high as 159° Fahrenheit. An ordinary lucifer-match does not ignite when simply pressed upon a smooth surface at 212°; but in the act of withdrawing it it takes fire, and the slightest friction upon such a surface of course ignites it.