_Causes of the Uniform High Temperature near the Equator._--It is popularly supposed that the uniform high temperature of the tropics is sufficiently explained by the greater altitude, and therefore greater heating-power, of the midday sun; but a little consideration will show that this alone by no means accounts for the phenomenon. The island of Java is situated in from six and a half to eight and a half degrees of south latitude, and in the month of June the sun’s altitude at noon will not be more than from 58° to 60°. In the same month at London, which is fifty-two and a half degrees of north latitude, the sun’s noonday altitude is 62°. But besides this difference of altitude in favour of London there is a still more important difference; for in Java the day is only about eleven and a half hours long in the month of June, while at London it is sixteen hours long, so that the total amount of sun-heat received by the earth must be then very much greater at London than at Batavia. Yet at the former place the mean temperature of the day and night is under 60° Fahr., while in the latter place it is 80° Fahr., the daily maximum being on the average in the one case about 68° and in the other about 89°. Neither does the temperature at the same place depend upon the height of the sun at noon; for at Batavia it is nearly vertical during October and February, but these are far from being the hottest months, which are May, June, and September; while December, January, and February are the coldest months, although then the sun attains nearly its greatest altitude. It is evident, therefore, that a difference of 30° in the altitude of the sun at noon has no apparent influence in raising the temperature of a place near the equator, and we must therefore conclude that other agencies are at work which often completely neutralise the effect which increased altitude must undoubtedly exert. There is another important difference between the temperate and tropical zones, in the direct heating effect of the sun’s rays independently of altitude. In England the noonday sun in the month of June rarely inconveniences us or produces any burning of the skin; while in the tropics, at almost any hour of the day, and when the sun has an elevation of only 40° or 50°, exposure to it for a few minutes will scorch a European so that the skin turns red, becomes painful, and often blisters or peels off. Almost every visitor to the tropics suffers from incautious exposure of the neck, the leg, or some other part of the body to the sun’s rays, which there possess a power as new, as it is at first sight inexplicable, for it is not accompanied by any extraordinary increase in the temperature of the air.