3S8 Prof. Necker m the History and Progress (^Geology. 
that study in its most comprehensive acceptation. The means 
of observation may be ameliorated, the result simplified or gene- 
ralised, but every where in the fundamental questions do we 
find the impress of the steps of Saussure upon the path of truth. 
It is not, therefore, so much the number, or even the import- 
ance of the detailed observations ; it is the spirit which has guid- 
ed him in the whole of his career, ^the spirit with which he has 
animated Dolomieu, Spallanzani, Palassou, and those who have 
immediately followed his traces in the purely philosophical in- 
vestigation of nature ; it is that spirit which he has excited, 
which renders him worthy of being considered as the illustrious 
representative of the new era of geology. 
( To he continued.) 
Art. XVI. — On the Numher and Situation of the Magnetic- 
Poles of the Earth. By Professor Hansteex 
rwj 
PIAT the magnet attracts iron was known to the natura- 
lists of Greece and Rome. If we strew iron-filings upon it, these 
cling with peculiar fastness to the two opposite ends, in which 
the greatest power thus seems to reside. If we hang up a mag- 
net by a thread, or allow it to swim in quicksilver, or place it on 
a small bit of wood floating in water, we shall find that it will 
never come to a state of rest, till the one end point to the north, 
and the other to the south. This quality of the magnet of point- 
ing, when it is left to move at perfect liberty, towards the north 
and south, the poles of the earth, is called its polarity ; and the 
two stronger ends its poles. On this polarity is founded the 
construction of the mariner’s compass, the needle or index of 
which is nothing else than a prismatic piece of tempered steel, 
which, by being rubbed on a magnet, has acquired the magnetic 
powers, and which is placed on a pivot, on which it is at liberty 
to turn itself in all directions. 
When this remarkable quality of the magnet became known 
to Europeans, is a matter hid in darkness. About the end of 
the 12th century, we find evident traces of the use of the com- 
pass. It is beyond doubt, that the Chinese were acquainted 
with it long before this period ; and it is highly probable, that 
* From the Christiania Journal of Natural Science. 
