OF FERRUGINOUS BODIES. 223 
the magnet, the power of the other pole is aug- 
‘mented to the greatest extent. 
38. If, by means of a compass needle, we were 
to ascertain the situation of the unapproached 
pole, both before and after the application of the 
iron to the other pole, we should find that the 
former pole recedes from the extremity of the 
magnet, or retires nearer to the magnet’s centre, 
by the approach of iron to the other pole. 
39. Now since the pole of a bar magnet operates 
more powerfully on a needle by the approach of 
iron to its other pole, (37), whilst at the same 
time the former pole recedes from the needle, 
(38), and consequently operates to disadvantage 
by an increase of distance, it appears obvious that 
the absolute gain of deflecting force derived from 
the approach of iron to the other pole, is much 
greater than the needle is calculated to indicate. 
The same reasoning applies to the magnet’s lift- 
ing power, which, in consequence of an increase 
of distance of the pole from the iron lifted, does 
not indicate the extent of power absolutely gained ; 
or rather, of magnetic force liberated by the ap- 
proach of iron to the other end of the magnet. 
