Chapter X: Book II: p. 78) as follows: “Of rocks magnetical, there are likewise

two relations; for some are delivered to be in the Indies and some in the extremity of the North and about the very pole. The Northern account is commonly ascribed unto Olaus Magnus, Archbishop of Upsala, who, out of his predecessors--Joannes, Saxo and others--compiled a history of some Northern Nations; but this assertion we have not discovered in that work of his which commonly passeth among us; and should believe his geography herein no more than that in the first line of his book, where he affirmeth that Biarmia (which is not 70 degrees in latitude) hath the pole for its zenith, and equinoctial for the horizon.”

In a Spanish book entitled “The Naval Theatre,” by Don Francisco de Seylas and Louera, we find two causes assigned for the variation of the declination; one is “the several mines of loadstones found in the several parts of the earth ...” the other being that “there is no doubt but large rocks of loadstones may affect the needles when near them ...” (“Philos. History ... Roy. Acad. Sc. at Paris,” London, 1742, Vol. II. pp. 279–280).

REFERENCES.--Claudus Ptolemæus, “Geographia,” lib. vii. cap.
2 (and others named by Bertelli Barnabita at foot of p. 21
of his “Pietro Peregrino de Maricourt,” Roma, 1868, viz.
Klaproth, “Lettre sur la Boussole,” Paris, 1834, p. 116; Thos.
H. Martin, “Observ. et Théor. des anciens,” Rome, 1865, p.
304; Steinschneider, “Intorno. alla calamita,” Roma, 1868);
also Albertus Magnus, Lugduni, 1651; Mr. (Thomas) Blundeville,
“His Exercises”; Fracastorio, in the seventh chapter of his
“De Sympathia et Antipathia”; F. Maurolycus, “Opuscula,” 1575,
p. 122a; Lipenius, “Navigatio Salomonis Ophiritica”; Paulus
Merula, “Cosmographia Generalis,” Leyden, 1605; Toussaincte de
Bessard, “Dialogue de la Longitude,” Rouen, 1574; U. Aldrovandi,
“Musæum Metallicum,” 1648, pp. 554, 563, wherein he alludes to
the magnetic mountains spoken of by Sir John Mandeville; Ninth
“Encycl. Brit.,” Vol. XVII. p. 752; also the entry at A.D.
1265–1321.

=A.D. 1558.=--Porta (Giambattista della), Italian natural philosopher (1540–1615), carries on a series of experiments with the magnet for the purpose of communicating intelligence at a distance. Of these experiments, he gives a full account in his “Magiæ Naturalis,” the first edition of which is said to have been published at Naples when Porta was but fifteen years of age (“Encycl. Brit.,” article “Optics”). Prof. Stanley Jones says this is the earliest work in which he has found allusions to a magnetic telegraph.

Porta’s observations are so extraordinary--and they attracted so much attention as to justify eighteen separate editions of his work in different languages prior to the year 1600--that extracts must needs here prove interesting. They are taken out of “Natural Magick in XX Bookes by John Baptist Porta, a Neapolitaine ... London 1658,” the seventh book of which treats “Of the wonders of the loadstone.”

_Proem_: “And to a friend that is at a far distance from us and fast shut up in prison, we may relate our minds; which I doubt not may be done by two mariner’s compasses, having the alphabet writ about them ...”

Chap. I (alluding to the loadstone):

“The Greeks do call it _Magnes_ from the place,
For that the Magnet’s hand it doth embrace.”

Nicander thinks the stone was so called--and so doth Pliny--from one _Magnes_, a shepherd.

In Chap. XVIII he states that “the situation makes the Vertues of the Stone contrary ... for the stone put above the table will do one thing, and another thing if it be put under the table ... that part that drew above will drive off beneath; and that will draw beneath that drove off above: that is, if you place the stone above and beneath in a perpendicular.”

In Chap. XXV, in allusion to “a long concatenation of iron rings,” he thus quotes Lucretius:

“A stone there is that men admire much
That makes rings hang in chains by touch.
Sometimes five or six links will be
Fast joyn’d together and agree.
All this vertue from the Stone ariseth,
Such force it hath ...”

Chap. XXVII alludes to the Statue hung by Dinocrates: “... but that is false, that Mahomet’s chest hangs by the roof of the Temple. Petrus Pellegrinus saith, he shewed in another work how that might be done: but that work is not to be found.... But I say it may be done--because I have now done it--to hold it fast by an invisible band, to hang in the air: onely so, that it be bound with a small thread beneath, that it may not rise higher: and then striving to catch hold of the stone above, it will hang in the air, and tremble and wag itself.”

In Chap. XXVIII he says that “Whilst the loadstone is moved under a table of wood, stone or any metal, except iron, the needle in the mariner’s compass will move above, as if there is no body between them. St. Augustine (‘Liber de Civitate Dei’) knew this experiment (likewise alluded to by Camillus Leonardus in his ‘Speculum Lapidum,’ published 1502). But that is much more wonderful that I have heerd: that if one hold a loadstone under a piece of silver, and put a piece of iron above the silver, as he moves his hand underneath that holds the stone, so will the iron move above; and the silver being in the middle, and suffering nothing, running so swiftly up and down, that the stone was pulled from the hand of the man, and took hold of the iron.”

Chap. XXX is headed: “A loadstone on a plate of iron, will not stir iron,” and he again quotes Lucretius:

“Pieces of iron I have seen
When onely brass was put between
Them and the Loadstone, to recoil:
Brass in the middle made this broil.”

In Chap. XXXII he tells us that an Italian “whose name was Amalphus ... knew not the Mariner’s Card, but stuck the needle in a reed, or a piece of wood, cross over: and he put the needles into a vessel full of water that they might flote freely: then carrying about the loadstone, the needles would follow it: which being taken away, as by a certain natural motion, the points of the needles would turn to the north pole: and, having found that, stand still.... Now the Mariner’s Compass is made, and a needle touched with the Loadstone, is so fitted to it, that, by discovering the pole by it, all other parts of the heavens are known. There is made a rundle with a Latin-navel upon a point of the same metal, that it may run roundly freely. Whereupon, by the touching onely of one end, the needle not alone partakes of the vertues of it, but of the other end also, whether it will or not....”

Chap. XLVIII is headed “Whether Garlick can hinder the vertues of the loadstone.” By Porta we are informed that “Plutarch saith Garlick is at great enmity with the loadstone; and such antipathy and hatred there is between these invisible creatures, that if a loadstone be smeered with Garlick, it will drive away iron from it,” which is confirmed by Ptolemy, who states “that the loadstone will not draw iron, if it be anoynted with Garlick; as Amber will no more draw straws, and other light things to it, if they be first steeped in oyl.” He found that when the loadstone “was all anoynted over the juice of Garlick, it did perform its office as well as if it had never been touched with it.”

In Chap. LIII Porta denies “that the diamond doth hinder the loadstone’s vertue.” “Some pretend,” says he, “there is so much discord between the qualities of the loadstone and the diamond, and they are so hateful, one against the other, and secret enemies, that if the diamond be put to the loadstone, it presently faints and loses all its forces. (Pliny.) The loadstone so disagreeth with the diamond, that if iron be laid by it, it will not let the loadstone draw it; and if the loadstone do attract it, it will snatch it away again from it. (St. Augustine.) I will say that I have read of the loadstone: how that, if the diamond be by it, it will not draw iron; and, if it do when it comes neer the diamond, it will let it fall” (Marbodeus, of the Loadstone ... Marbodei Galli ... de lapidibus pretiosis Enchiridion ... Freiburg, 1530, 1531):

“All loadstones by their vertue iron draw;
But of the diamond it stands in awe:
Taking the iron from’t by Nature’s Law.”

“I tried this often, and found it false; and that there is no truth in it.”

With reference to the above, see Plat (at A.D. 1653), who also alludes to the fact of the softening of the diamond with Goat’s blood. This is alluded to by Porta in the next chapter.