Thus measured, it will be seen how tremendously mysterious is the power of magnetism, and how potent an influence it must possess over animate and inanimate nature! And not one of its least wonderful mysteries is its singular exception to the character of stability and permanence. The configuration of our globe, the distribution of temperature in its interior, the tides and currents of the ocean, the general course of winds, and the affections of climate—all these are appreciably constant. But magnetism, that subtle, undefinable fluid, is perpetually undergoing a change, and of so rapid a nature, that it becomes necessary to assume epochs, which ought not to be more than ten years apart, to which every observation should be reduced. The extreme importance of knowing the exact amount of magnetic variation can scarcely be overrated for maritime purposes; and the establishment of a complete magnetical theory, based on an extensive series of observations, must be regarded as a desideratum by the first nautical country. The numerous magnetical surveys that have been made by our government, taken in conjunction with those in progress on the continent of Europe, and particularly in the Austrian dominions, give a full promise of the speedy realization of M. Humboldt’s wish, so earnestly expressed, that the materials of the first general magnetic map of the globe should be assembled; and even permit the anticipation, that the first normal epoch of such a map will be but little removed from the present year. EARLY HISTORY OF THE USE OF COAL. (FROM CHAMBERS’S EDINBURGH JOURNAL.)