76 
FIFTH RETORT— 1835 . 
second, as the square; and third, as the cube, of the distance of 
the magnetic point from the centre of the magnet: and in which 
the distribution of the intensity along the magnetic axis is con¬ 
sidered to vary, first, as the simple distance of the particles from 
the middle point; second, as the square ; and third, as the cube 
of that distance. It is shown by the comparison, first, as regards 
the distance of the magnetic point and the centre of the magnet, 
that when the displacements are computed in the inverse propor¬ 
tion of the simple distance or of the cube, they differ widely from 
those observed; but that when computed as the squares, the ac¬ 
cordance of calculation and experiment is satisfactory through¬ 
out the series. Second in regard to the distribution of the in¬ 
tensity along the magnetic axis, that the agreement is best in 
these experiments when the magnetic intensity of the particles is 
taken as the square of the distance from the middle point of the 
magnet. 
o 
The experiments, therefore, indicate the following elementary 
laws, viz. 
1. That the attractive force with which two magnetic points 
influence each other is inversely as the square of their 
distance apart. 
2. That the force in the axis of a linear magnet increases as 
the square of the distance from the middle point; or, that 
the absolute intensity of each point in the axis is pro¬ 
portional to the square of its distance from the magnetic 
centre. 
The first law is the same which was originally derived by 
Mayer from experiments communicated to the Royal Society of 
Sciences at Gottingen; it has been since confirmed by other 
philosophers, and is in full accordance with the experiments of 
M. Hansteen. 
A corroboration of the second law is considered to be obtained 
from other experiments, subsequently related, in which two li¬ 
near magnets were employed for the purpose of examining the 
laws of their mutual action. M. Hansteen also notices the ex¬ 
periments of Professor Steinhausen, which lead to the same in¬ 
ference. He concludes, therefore, that there is at least strong 
probability in favour of the second law; and as, moreover, that 
law is only of importance in small distances from the magnet, ap¬ 
proaching contact,—and as in its application to the phenomena 
of terrestrial magnetism the distances are always so considerable 
as to render almost imperceptible the effect of differences in the 
distribution of intensity in its magnet itself, its adoption on this 
occasion cannot give rise to any material error, even if it should 
not ultimately prove to be the true law. 
