We have arrived at a momentous epoch in the history of the sea. It was at this period that the mariner's compass was--we do not say invented--but introduced into European navigation. That this admirable instrument, which, in half a century, changed the face of the earth, by leading to the discovery of America and thus proving the sphericity of the world, should remain unclaimed by its author, and that we are unable to point to him who thus blessed and benefited his race; must always be a subject of regret. So far from being able to name the individual to whom the invention is due, it has long been deemed impossible to fix even upon the nation who first used the needle at sea. We hope, however, by availing ourselves of recent researches made in France, to arrive at a conclusion not only satisfactory, but inevitable. In tracing the history of the compass, we must naturally begin with the magnet. The ancients were fully acquainted with the loadstone, and with its power of attracting iron, though they were totally ignorant of its polarity. That they were so, is evident from the fact that the classic authors and ancient works upon navigation and kindred subjects do not furnish one word upon the subject. Claudian has left, in one of his idyls, a long description of the stone, and of its peculiar, indeed, magical, affinity for iron. Had he entertained the most distant idea that this stone could communicate to a steel needle the power of indicating the north, it is not to be supposed for an instant that he would have omitted mentioning it. The earliest name of the loadstone was Hercules' Stone, which was soon changed to _magnes_, from the fact that it was found in abundance in a region called Magnesia, in Lydia. Hence our word magnet. It was not till the fourth century of our era that the quality of repelling as well as of attracting iron seems to have been discovered. Marcellus, the physician of Theodosius the Great, is the first author who mentions this new quality. The Romans, who acquired a knowledge of the magnet from the Greeks, preserved the name, though several of their authors, and Pliny among them, mention a tradition, that the magnet was so called from a shepherd named Magnes, who was the first to discover a mine of loadstone, by the nails in his shoes clinging to the metal. The first mention in European history of the polarity of the magnetized needle, and of its importance to mariners, occurs in a satirical French poem written in 1190 by one Guyot de Provins. His object was to level, by implication, an invective against the Court of Rome; and he did it in the following neat manner. The translator has endeavored to preserve the quaint style of the original: