Terrestrial Magnetism . 
125 
The history of the science as detailed in these pages 
lias been gathered from various sources, and from the 
best authorities which it was possible to procure at the 
moment. 
It is not surprising that the attractive and repulsive 
powers of the natural magnet, or loadstone, should, 
from the earliest times, have engaged the attention of 
philosophers, and have excited amongst them a lively 
curiosity to ascertain the causes that produced such 
phenomena: accordingly we find that the subject has 
afforded for many ages a most fruitful field for speculative 
theories. 
The ancients indulged many wild and superstitious 
fancies upon the subject: by some it was ascribed to the 
secret influence of a mind, or soul, residing in magnets ; 
others endeavoured to account for it by a sympathy exist¬ 
ing between the loadstone and iron ; while, according to 
a third hypothesis, it was asserted that iron was the 
natural food of the magnet. In more modern days two 
hypotheses have been advanced to account for the 
phenomena of magnetism : one is known as that of 
GEpinus, who imagined that it might be derived from the 
agency of a peculiar fluid, having properties very similar 
to those of the electric fluid, but which acted exclusively 
upon iron,—which is the case as far as respects attrac¬ 
tion, repulsion, and induction,—and that there existed 
in all bodies capable of acquiring magnetic properties a 
subtle fluid, which he termed the magnetic fluid. He 
then supposed that the particles of this fluid repelled 
one another with a force which decreased as the distance 
increased, and that they were mutually attracted and 
repelled by particles of iron, with a force varying 
according to the same law. The other hypothesis is 
founded upon the supposition that two magnetic fluids 
reside in the particles of iron which are incapable of 
