"Among the most powerful, most wonderful, and most mysterious agents in the economy of the physical universe, is the magnet. Its attractive properties, its perpetual tendency to the poles of the earth and of the heavens, and its exclusive sympathies with one of the mineral productions of the earth, have been brought within the scope of human observation at different periods of the history of mankind, separated by the distance of many centuries from each other. The attractive power of the magnet was known in ages of antiquity so remote that it transcends even the remembrance of the name of its first discoverer, and the time of its accession to the mass of human knowledge. Its polarity, or, at least, the application of that property to the purposes of navigation beyond the sight of land, was unknown in Europe, and probably throughout the world, until the twelfth or thirteenth century of the Christian era; and its horizontal variation from the tendency directly to the pole was first perceived by Christopher Columbus, in that transcendent voyage of discovery which gave a new hemisphere to the industry and intelligence of civilized man;--an incident then so alarming to him and his company, that, but for the inflexible and persevering spirit of this intrepid and daring mariner, it would have sunk them into despair, and buried the New World for ages upon ages longer from the knowledge of the Old. Centuries have again passed away, disclosing gradually new properties of the magnet to the ardent and eager pursuit of human curiosity, still stimulated by constant observation of the phenomena connected with this metallic substance, dug from the bowels of the earth, yet seeming more and more to elude or defy all the ordinary laws of matter. Thus, in the process of observation to ascertain the horizontal variation of the needle from its polar direction, it was found that it differed in intensity in the different regions of the earth and the seas; that its variations were affected by different causes, some tending in the same direction, alternately east and west, through a succession of years, of ages, even of centuries, and others accomplishing their circle of existence from day to day, perhaps from hour to hour, or at stated hours of the day. It was found that there was a perpendicular as well as a horizontal deviation from the polar direction; and it became a matter of anxious inquiry to ascertain the intensity both of the dip and variation of the needle at every spot on the surface of the globe. It was inferred, from the different intensities of variation in different latitudes, that there were magnetic poles not coincident with those of the earth; and the northern of these poles has been recently traced to its actual location by the British circumnavigators, Parry and Ross.