MS Hints for the Formation of 
movements of these magnets. But in the system, which 
does not admit these internal magnets, it is asked, Whe- 
ther the changes of declination might not depend on move” 
ments which produce the change of obliquity, precession, 
nutation, and perhaps other phenomena or inequalities of 
that kind.f 
6. With regard to diurnal variations, an English philo- 
sopher, Mr. Canton, considering that it is proved by ex- 
perience that heat diminishes the force of the magnet, 
thought that the solar rays, by heating the earth, must 
lessen the attractive force of the grand magnet contained 
in it ; and lie thence deduced, as will be seen hereafter, an 
explanation of these variations. But Mr. Canton did not 
reflect on what was clearly seen by M. jEpinus, that this 
magnet, if it exists, is sunk to too great a depth in the 
earth for the action of the solar rays, or at least the varia- 
tions of that action, in the morning and evening, to be able 
to penetrate to it. We may, however, apply to the fer- 
ruginous minerals, dispersed in abundance over the sur- 
face of the earth, what Mr. Canton supposed, in regard 
to the grand magnet contained in its bosom ; and then, if 
we admit that these minerals exercise any action on the 
j- JEpinus gives another explanation independent of these movements. It may 
be possible, according to this philosopher, that the declination of the magnetic 
needle arises, in general, from the irregular figure of the nucleus of the magne. 
tic globe, or from an unequal distribution of the fluid in its interior part : and to 
account for the variation of this declination in one place, in the course of time we 
might suppose that the figure of the nucleus, or the distribution of the fluid it 
contains, is itself variable. JEpinus presumes also, that the action of the iron 
mines dispersed throughout the bosom of the globe, may have an influence on 
the variation in question ; and may, perhaps, be the sole cause of it. Tentame? : 
theories electr. et magnet, p. 268, 27b 334. 
This philosopher wishes that men of science, who have an opportunity of be 
ing near a mine of loadstone, would determine, by observation, whether the 
masses of this mineral, before they are taken from the bowels of the earth, have 
their poles disposed, in regard to the poles of the world, like those of needles 
freely suspended and whether, in certain masses, the poles are not in an inverse 
direction, of which he shews the possibility by means of consequent points. Ibid 
p. 333. —Note of the same. 
