A Course of Eight Lectures; On Electricity, Galvanism, Magnetism, and Electro-Magnetism

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1839. Not illustrated. Excerpt: ... LECTURE V. ON MAGNETISM. Although the attractive power of the loadstone appears to have been known in times of very remote antiquity, and its properties studied even during the dark ages, yet its directive power, and that of a needle touched or rubbed with it, seems to be the discovery of modern times. In an old French poem, called La Bible Guyot, which is contained in a curious quarto manuscript of the thirteenth century, still existing in the Royal Library at Paris, and in several other authors, there are notices which prove that the mariner's compass was known in the twelfth century; and Cardinal James de Vitri, who nourished about the year 1200, mentions the magnetic needle in his history of Jerusalem; and he adds, that it was of indispensable utility to those who travelled by sea. A Neapolitan named Flavio Gioia, who lived in the thirteenth century, has been regarded by many as the inventer of the compass. Dr. Gilbert affirms that Paulus Venetus brought the compass from China to Italy in 1260; and Ludi Vestomannus asserts, that about 1500, he saw a pilot in the East Indies direct his course by a magnetic needle like those now in use. The variation of the needle was discovered two hundred years before the time of Columbus, but the variation of the variation, that is, the fact that the variation was not a constant quantity, but varied in different latitudes, was first noticed by the discoverer of America, as appears from the following extract from Irving's Life and Voyages of Columbus, vol. 1, p. 201. On the 13th of September, 1492, he perceived about night-fall, that the needle instead of pointing to the north-star, varied but half a point, or between five and six degrees, to the north-west, and still more on the following morning. Struck with this circumst...