254 PECULIARITIES IN THE MAGNETISM 
needle was now vibrated under the dominion of 
both the magnetic force of the terrestrially pola- 
rized iron, and that of the earth itself, and was 
found to perform 1:5 vibrations per second. 
98. Having thus obtained the rate of vibration 
under these three different circumstances, it was 
easy to ascertain the ratio of the magnetic force 
exercised by the iron, whilst under the influence 
of the steel bars, and whilst under the influence 
of terrestrial magnetism alone. The ratio of the 
vibrations being as 12 : 1:5, whilst the iron acted 
in concert with the force of terrestrial magnetism ; 
and the latter alone producing one vibration in 
the same interval of time ; the ratio of the forces 
of the iron, under the influence of the bar mag- 
nets, and of the earth is as (12?—1°) :(1°5°— 1’,) 
or 114: 1 nearly. 
99. This ratio ascertained, the system of mag- 
nets and the counteracting magnet, were replaced, 
so as to give permission to the needle to swing as 
if under the force of terrestrial magnetism only. 
The needle was now drawn 90° from the magnetic 
meridian, by means of a small magnet, and per- 
mitted to rest in that position whilst the iron was 
heating. 
