of the Magnetic Poles of the Earth. i 115 
‘the close of the eleventh century, the polarity of the magnet 
must then have been known in the North, although the passage 
just quoted does not imply the actual existence of a regular 
‘compass*. 
The circumstance of a freely moveable magnet turning con- 
stantly with its poles to the north or south, leads us to the 
“eonclusion that the earth itself must be a large magnet, which 
has near the geographical arctic pole a pole like that of the 
magnetic needle turned towards the south, and near the ant- 
arctic geographical pole a magnetic pole like that of the mag- 
netic needle turned towards the north. If the magnetic needle 
were, in every part of the earth, to point due north and south, we 
might say without hesitation thatthe magnetic poles correspond- 
ed with the geographical. However, after the compass had been 
used for several centuries, it was found, on closer investigation, 
that the magnetic needle actually deviates from the meridian : 
further, 
* This work was published at Copenhagen in 1774, under the title of 
Islands Landnamabok. Hoe est; “ Liber originum Islandiz. Versione La- 
tina, lectionibus variantibus et rerum, personarum, locorum, nec non vocum 
rarissimarum indicibus illustratus. Ex manuscriptis Legati Magnzeani. 4.” 
The editor of this book names himself at the end of the preface Johannes 
Finnzus. This work, in which the position and condition of Iceland, as 
well as the history of its industrious inhabitants, is given at large, had several 
authors. The first of them was (Landnamabok, p. 378), Arius Polyhistor 
(Ari prestrhina Frodi Thorgilssun), born in the year 1068; and the last, 
Hauk, son of Erlend (Haukr Erlendssun), who died in 1334. For in the 
Latin version (Lib. v. cap. 15, p. 378) it is said: ‘‘ Hunc autem librum Do- 
minus Haukus Erlendi filius secundum librum, quem Dominus Sturla filius 
Thordi Nomophylax vir eruditissimus concinnaverat, et secundum alium 
librum, a Styrmere Polyhistore exaratum, seripsit, et ex quovis libro ea que 
uberius enarrata erant, retinuit, maxima autem ex parte uterque liber eadem 
referebant; non igitur mirum hunc Landnamabok omnibus aliis prolixi- 
orem esse.” The passage quoted by Professor Hansteen appears indeed 
in the beginning of the work, and it might thence be inferred that it was 
written by Arius: yet this is not certain, and it might easily have. been added 
by later editors. Moreover the editor says in reference to this passage 
(p. 7), “ Hoc caput,” the second in which the passage appears, “ est secun- 
dum Hauksbok,” as he calls it according to its author Hauk ; and, what is 
more, the passage (according to the editor) is missing in three different 
manuscripts. It is, therefore, yet to be doubted whether the passage be 
genuine, and whether the Icelanders knew the magnet at so early a period. 
That they knew the deviation of the needle as early as 1269, appears 
from a manuscript of Adsigerius in the library at Leyden, and which Pro- 
fessor Hansteen (Investigations respecting the Magnetism of the Earth, 
p. 403) seems to have known only from Thevenot’s account. The words, 
- according to Van Swinden (Bibliotheque Universelle, tom. xxiv. p. 262), are 
as follows: “* Nota quod partem meridionalem acus, in usu directorii de- 
bemus facere declinare per unum punctum versus occidens, et hoc debet 
fieri per declinationem partis septentrionalis ad oriens, quia pars meridiana 
instrumenti divisionibus caret. Nota quod lapis magnes, ut ut exactius con- 
sectatus tamen non directe tendit ad polos, sed pars, quae ad meridiem 
»Q tendere 
