Remarks on Professor Hansteen'’s 
lU 
Mr Hansteen’s mode of experimenting seems to be nearly 
identical with that followed by Hawksbee and Lambert ; but 
the consequences deduced from his experiments belong entirely 
to himself. Having assumed (for he does not succeed in prov- 
ing) that the attraction or repulsion between any two magnetic 
particles must be directly as the intensity of their force, and in- 
versely as some power (t) of their mutual distance; and having, 
in like manner, assumed that the magnetic intensity of any par- 
ticle must be proportional to some power (r) of its distance from 
the centre of the magnet ; he easily finds a general expression 
for the effect which a linear magnet would have upon a magne- 
tic point situated any where in the axis produced. The for- 
mula isF = 
I 
dx 
(a — xy 
x^ dx 
(a q- xy 
; where F (multiplied by 
a constant quantity depending on the degrees of magnetism 
which the point and the line possess,) represents the force ; a*, 
the half axis of the linear magnet ; and a the distance of the 
point from the centre of that linear magnet. By assigning diffe- 
rent values in succession to t and r, it is easy to calculate (F) 
the effect for each of these values, with a given magnet (x), at 
a given distance (a) from the point to be acted on. It will then 
appear with which of the values, successively assigned to t and 
r, the results of experiment agree most completely. 
The method by which Mr Hansteen endeavours to find the 
effect of a linear magnet upon a magnetic particle, is liable, like 
every such method, to the uncertainty of employing a small 
needle instead of a point, and a prism instead of a line. It can 
be shewn, however, that the size of the needle, and the thickness 
of the prism, have scarcely any perceptible influence in the pre- 
^nt case. The experiment proceeds upon the principle of op- 
posing the constant magnetic force of the earth to the force of 
an artificial magnet. The latter is made to yary, by varying 
the distance. ’ 
Upon a horizontal table a very delicate compass was placed, 
so that its needle pointed exactly to 0° ; from beneath the centre 
of this needle, and perpendicular to its direction, or to the mag- 
netic meridian, a straight line was drawn upon the table, and 
4ivided into portions such that ten of them were equal to the 
