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thagoras, Dion, Pericles, Sulpitius1, and the EthiopiansR. And we are assured by Macrobius, that a regular series had been observed in Egypt, 1,200 years before the birth of Alexander. The obligations of Copernicus to Pythagoras are universally known: Philolaus and Statius3 taught the diurnal motion of the earth: Meton invented the lunar cycle: Democritus, Anaxagoras, Plato*, and Lucretius, taught a plurality of worlds; and that the spots on the moon's disc were the shadows of high mountains: while Anaxagoras ascertained the causes of thunder and lightning. The rotundity of the globe was known to Virgil'; and that the fixed stars are suns, shining to other systems, was not only known to Manilius, but described by Lucretius. Chiron invented the sphere; Anaximander maps and globes; and Eratosthenes the armillary sphere. Berosus taught the art of dialling; Diophantes algebra; and Menechmus conic sections. The Greeks assure us, that geometry took its rise in Egypt: but Josephus insists, that the Egyptians received it from the Hebrews. Indeed it

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6 Cesar, Pliny, and Seneca, describe fires on the spears of soldiers; phenomena, frequently seen in warm countries. Camöens (book v.) describes them, as appearing on the spindles of the masts of Gama's ships; and takes occasion to celebrate the wonders of nature; and to inculcate the advantage of studying her laws. These phenomena are called St. Helme's Fires by the Spaniards; and Fires of St. Peter and St. Nicholas by the Italians. Ctesias relates, that he witnessed the experiment of iron, concealed in the ground, averting the consequences of storms.

7 Georg. i. 1. 242.

8 Bryant's Analysis, vol. ii. p. 482, 4. .

would have been impossible to have built any one of the towers, temples, or cities, which the Chaldeans are said to have built, without a knowledge of this essential art. Aristarchus and Nicetas of Syracuse taught the movement of the earth through the circle of the zodiac; and Dionysius of Alexandria discovered that period of the solar year, afterwards introduced to the Roman calendar by Julius Cæsar.

Memnon, the Egyptian, first traced the sounds of the human voice to those simple elements, by which the whole circle of knowledge might be imprinted. He invented letters in the year before Christ 1822; and a Phenician carried them into Greece in 1493. The properties of magnetical substances, too, were not entirely unknown. Diodorus relates, that Abaris, the celebrated Hyperborean, was conveyed to Greece, over mountains, rivers and seas, on an enchanted arrow. It is something more than probable, that this enchanted instrument was a magnet, pointed like an arrow. In such case, Abaris must have been acquainted with its polarity, as well as with its power of attraction. It is not a little remarkable, too, that the courses of ships, winds, &c. are still denoted on our maps and globes, by flying arrows. That the magnet was known to the Persians, Hyde gives some probable reasons to suspect1; and that it was used in China, long before it was in Europe, is almost certain; notwithstanding the assertions of Niebuhr and Sir William Jones. Stukely is, however, probably in error, when he supposes, that Abury Temple, and the solar one, at Stone

VOL. II.

De Religione Veterum Persarum, p. 189.

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henge, were fixed in their mathematical situations in respect to the cardinal points, by a magnetic compass: and Mons. Bailli makes the subject ridiculous, when he asserts, that it was even known to the antediluvians.

In the early records of observation, the magnetic needle declined towards the east. In 1558 it varied (London) to the east 11° 15'. This declination ceased in Europe about the middle of the seventeenth century; when it pointed due north and south. Soon after this, it declined towards the west. Of late, this declination has been diminishing, and the needle is now reclining to the north. This deviation, however, is subject to frequent variation. Professor Oersted, in a paper published by the Royal Society of Copenhagen, has observed, that during the day, the western deviation is greatest about two in the afternoon; and its greatest annual one in the month of September. Colonel Beaufoy observed, that the magnetic variation to the westward of true north had increased till February and March 1819; when it arrived at its maximum. Since then it has uniformly decreased. The western variation had been on the increase since 1657. Recupero informed Brydone', that the needle upon Mount Etna, soon after the eruption of 1755, was agitated with much violence for some time; and then lost its magnetical power entirely. On the iron mountain of Southern Africa, belonging to the Kora Hottentots, the needle, by being placed on fragments of a rock, points differently on different fragments. On some it loses its polarity entirely; on others it points to the south; on some

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it vibrates with violence; and on others it turns round with great celerity. At sea, near a certain part of the island of Elba, mariners steer without a compass, which is also sensibly affected in the isle of Canny, one of the Hebrides:-as well as on several of the hills in Australia', where it flies round with velocity, and suddenly settles at opposite points, the north point turning south. Mr. M'Bride and Captain Ross state, that the needle loses its magnetic virtue in Davis' Straits; in consequence of which the whale captains steer by the land, and through channels in the ice. Two Greenland ships, the North Pole and the William and Ann of Leith, having entered Davis' Straits, they pursued their course till they reached an opening, which, they supposed, was Lancaster Sound. During their stay in this part of the coast, it was discovered, that the compasses of both ships, whenever they approached within five or six miles to the north shore, which is rugged and mountainous, lost their magnetic virtue entirely; standing in any direction, to which they were placed, without indicating the least appearance of being attracted either one way or the other. But as soon as the ships reached beyond five or six miles from the land towards the middle of the Straits, the needles again acquired their usual power, and exercised it without any apparent obstruction.

Lieut. Parry left England in May 1819. He followed Captain Ross' track into Davis' Straits to Baffin's Bay; and

1 Oxley Jour. in Australia, p. 259-p. 278.

2 Voy. of Disc. to Arctic Regions, Appendix, p. 19. 4to.

through Lancaster Sound proceeded westward, until he arrived at about 115° west longitude; which he reached the 28th of September. Here he was stopped by the winter: but he cut his way two miles through the ice, and got. into a harbour of an island, which he called Melville Island. In this spot he stopped till the first of August in the following year; when the ice broke. In this voyage Lieutenant Parry observed, that the magnet held a variation of 126° west and only about one hundred and fifty miles farther of 128° east; so that the ship seems to have made a circuit round the magnetic pole, which some have supposed to be situate on the American continent, between the longitudes of 90° and 120°; and below the latitude of 70°. It may be here observed, that Barlow has recently discovered, that the magnetic quality of iron resides wholly in the surface. Thus an iron shell, weighing ten pounds, will act as powerfully as an iron ball of one hundred times its weight, having the same external dimensions. It has also been lately ascertained, that the violet rays of the prismatic spectrum have a magnetic power. This was discovered by Morrichini of Rome. The Marquis Ridolfi also proved, that needles, magnetized by these rays, have the properties of needles, magnetized by means of a loadstone. They vibrate on a pivot; and their points turn invariably to the north. Their heteronomous poles attract, and their homonomous ones repel each other.

The gravity and elasticity of the air was familiar to Aristotle and Seneca; Pherecydes, the master of Pythagoras, foretold an earthquake by drinking the waters ;

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