Humboldt, at Caraccas, in South America, has made some interesting observations on the motion of the barometer near the equator. "I have read," says he, "in the transactions of the Bengal society, that the barometer rises and falls there regularly every twenty-four hours. Here, in South America, its motion is more astonishing. There are four atmospherical tides every twenty-four hours, which depend only on the attraction of the sun. The mercury falls from nine o'clock in the morning till four o'clock in the evening. It rises from four till eleven o'clock; it falls from eleven o'clock till half past four in the morning; it reascends, from that time till nine o'clock: neither winds, storms, nor earthquakes, have any influence on this motion." This fact goes a great way towards proving the general truth of Mr. Howard's theory, given in the Philosophical Magazine, Vol. VII.