1S6 on Professor riiinsteen’s 
speedy in its progress. The double vortices of Des Cartes, were 
as unfortunate here as in astronomy, though altered and mould- 
ed with all the mathematical acumen of Euler and Bernoulli. 
They produced no useful result ; and the investigation of this 
matter may be said to have commenced with Hawksbee‘’s expe- 
riments upon the law of magnetic attraction and repulsion, pu- 
blished in the Philosophical Transactions for the year 171S. 
The discovery of saturation^ due to the labours of Knight, Du 
Hamel, iEpinus, and others, formed an important step; but the 
ratio according to which a magnetic particle attracts or repels 
another, was not ascertained with any degree of precision, till 
the task was undertaken by Coulomb, almost in our own times. 
The causes of so slow an advancement are easy to discover. 
The extreme difficulty of finding decisive experiments, has re- 
tarded or misled all inquiries directed to discover the nature of 
magnetic force. And as to the phenomena of terrestrial mag- 
netism, — the long period which the variation, dip, and intensity 
require to complete their revolution, and present the same suc- 
cession of appearances ; the errors to which observations of this 
sort are perpetually liable ; the small number of such observa- 
tions ; the dispersed state in which all of them must be gather- 
ed from voyages, undertaken generally with quite different views, 
have materially contributed to perpetuate ihe obscurity that still 
conceals this department of science. 
But the present seems a more auspicious period. So far as 
regards the nature of magnetic attraction and repulsion, a few 
of its laws appear to be pointed out with tolerable accuracy : 
the art of experimenting has received fresh improvements ; and 
attempts at least have been made to bring its results under the 
dominion of mathematical analysis. As to the magnetism of the 
earth, not only is the attention of seamen more generally direct- 
ed to the changes of their compass, but the discoveries of Flin- 
ders and others have introduced a degree of correctness hitherto 
unknown in such inquiries. It is a subject highly deserving 
our attention ; and even if at present the variation of the needle, 
stationary in most parts of Europe, seemingly regressive in 
others, did not solicit all the watchfulness of naturalists, the 
science itself, besides the immediate and valuable application of 
its discoveries to the purposes of navigation, promises to de- 
2 
