388 
Mil DEUCHAll'S ACCOUNT 
with an iron armature ; and when they came into Mr San^ 
derson's possession, were supposed to have but a very trif- 
ling magnetic power. A report of the great size of these 
loadstones was very rapidly circulated, and many gentle- 
men called to examine them, who generally evinced their 
surprise that so little attractive power was displayed ; but 
it is rather extraordinary that none of them traced out the 
cause, which we can only attribute to the rusty state in 
which the magnets were at the time : be this, however, the 
case or not, there can be little doubt that the full energy 
of these valuable minerals might still have remained latent, 
as they were for some time laid by as nearly useless, had 
not Mr Sanderson thought of cleaning them, to see w^hat 
effect that might have. For which purpose, the iron arma- 
ture was removed ; and this was scarcely done, when the 
cause of the inactivity was found to have rested in the 
armature, for the unarmed loadstone now lifted pieces of 
iron. They were thereafter armed with copper and brass, 
and began to exhibit an increasing power, as additional 
v/eights were added to them. 
It may appear, at first view of the circumstance, that the 
person who armed these magnets with iron, displayed little 
knowledge of magnetism ; but upon considering it more 
maturely, we will form an opposite opinion. Let us for a 
moment trace the effect of such an armature. The two 
surfaces, upon which the artificial poles are placed, present 
innumerable magnetic points, or so far combined poles, 
' — and soft iron has the power of receiving and convey- 
ing these to a focus, as it were. Now, suppose N (see 
fig. 2.) to be a magnet, and the lines OP and RS its two 
polar surfaces ; if we put a slip of soft iron round the por- 
tion marked AB, then that soft iron receives the magnet- 
ism of all the polar surface which it covers, and conveys it 
round in a circle, and vr'dl thus take awny so much of the 
