252 PECULIARITIES IN THE MAGNETISM 
the magnetic forces which the iron bar, whilst cold, 
and terrestrially magnetized, exercised on the 
needle, compared with that which it would display 
whilst under the influence of a powerful system 
of bar magnets employed in the investigation, I 
had recourse to the method of vibration. 
94. The vibrations of the needle by the force 
of terrestrial magnetism alone, independently of 
the presence of the iron, were ascertained to be 
nearly at the rate of one per second of time ; and, 
in order to facilitate calculation, they were, by 
means of a counteracting magnet, reduced to the 
same standard, when under the influence of the 
system of bar-magnets placed horizontally in the 
magnetic north of the needle; the pivot of the 
latter being eight inches distant from the vicinal 
pole. The compass-box was elevated on a brick 
about four inches and a half above the level of 
the system of magnets. 
95. The iron bar was now placed with one end 
on the system of magnets, and the other end 
resting on the edges of the brick, with its axis in 
the magnetic meridian. The vicinal end of the 
iron was two inches from the pivot of the needle, 
