SUPPLEMENT. 
n 
In order to show the incompatibility of the observed laws of 
terrestrial magnetism with the supposition of the earth itself be* 
ing a magnet, and at the same time their accordance with the 
laws, which appertain to a body whose magnetism is induced 
by electricity, it will be necessary to trace a retrospective view 
of the several discoveries which have been made connected with 
these subjects, since the commencement of the present century, 
and particularly within the last ten or twelve years ; at the same 
time it will not be uninteresting, nor by any means devoid of 
instruction, to trace the source of the discovery of the magnet to 
the very period when a further light has been thrown upon it, by 
the discoveries of Commander Ross on the actually supposed 
position of the magnetic pole. 
It would be here to little purpose to inquire particularly 
whether the magnet had its name from the shepherd Magnus, 
who, as Nicander and Pliny affirm, discovered it upon Mount 
Ida, by the iron of his crook, and the nails in his shoes, or 
whether it was so titled from Magnesia, that part of Lydia, where, 
according to Lucretius, it was first found. The Grecians, indeed, 
who were acquainted with the various names it then went by, 
and likewise with its attractive property, have sometimes called 
it si derites, from oiSvgog, iron ; but more frequently the Heraclean 
stone, from the city of Heraclea, in Magnesia; and Snellius may 
be right in saying that Euripides was the first who gave it the 
name of magnes, though Sophocles calls it lapis Lydius . 
With respect to the properties of the magnet, Father Kircher 
endeavors to prove, that its attraction was known to the Hebrews, 
and from Plutarch, it seems to appear that the Egyptians were 
not ignorant of it. Pythagoras, Ptolemy, Hippocrates, Empe¬ 
docles, Democritus, Leucippus, Epicurus, and many more of the 
ancients, knew and admired this wonderful property of the 
magnet. It was on account of this quality that Thales and 
Anaxagoras gave it a soul; and Plato, who called it the stone of 
Hercules, said that the cause of its attraction was divine. 
The discovery of the verticity or directive property of the 
magnet or loadstone, and the communication of that verticity to 
iron, or, in other words, the invention of the mariner’s compass. 
