Inquiries respecting the Magnetism of the Earth. 
mathematics, and his work is sprinkled with ingenious and strik- 
ing, if not always sound ideas, that agreeably relieve the dry 
details in which it of necessity engages, and induce us to look 
with some impatience for the appearance of the second part, to be 
employed in considering the optical phenomena connected with 
terrestrial magnetism. It is matter of regret, however, that the 
order in which the diversified contents of the present volume are 
brought forward, is rather apparent than real, and that the lan- 
guage in which they are delivered is not more generally acces- 
sible to men of science. Under a compressed form, a transla- 
tion of the work into French or English might have been an. 
acceptable service. In the brief abstract which we propose to 
give of it, our attention must be limited to a few of the more 
prominent objects. Such as wish to become acquainted with the 
expanded reasonings, and mth the facts on which they are 
founded, will find ample gratification in the work itself. 
If ever a knowledge of the magnetical phenomena manifested 
by the earth is attained, its basis must evidently rest on an ac- 
curate investigation of the properties possessed by such magnets 
as we have it in our power to submit to experiments. The laws 
by which the attractive and repulsive forces of the loadstone ex- 
ert themselves, have accordingly long formed a prominent object 
of research : and though our acquaintance with the figure, mag- 
nitude, and forces of the terrestrial magnet is yet in far too im- 
perfect a state to allow the employment of such laws, with com- 
plete advantage, in explaining its action ; our inquiries into the 
subject of the variation and dip are naturally preceded by an 
examination of what has been done in this division of the sci- 
ence. Mr Hansteen’s theory, indeed, professes to be the empi- 
rical result of a comparison instituted among all such observa- 
tions as were accessible, and seemed worthy of credit ; yet, as the 
speculative conclusions deduced from them ought to contain at 
least nothing contradictory to the established properties of natu- 
ral magnets, and consequently presuppose a knowledge, of these 
properties, we shall begin with his fifth chapter, entitled Ma- 
thematical Theory of the Magnet.” 
On observing the forces of a natural or artificial magnet to 
be accumulated at each extremity or pole, and to attract or re- 
pel more or less feebly according to circumstances ; the question 
VOL. III. NO. 5 . JULY 1820 . 
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