18 Mr Harris on Magnetic Intensity by the 
described (29). The force, as again estimated at each pole by 
the magnetimeter, was now doubled, and the retarding force on 
the copper again observed. In this case the latter was also found 
to be doubled. 
Thefollowing Table comprises the results of this experiment. 
TABLE I. 
Tension by Attraction. | Tension by Vib. of Ring. 
Distance of Lron 0.25. | Distance of Poles 0,9. 
) 100 
5 cua 1 = 0.818 
10° i = 1.631 
= —_—l 
38 
The vibrations of the ring were observed between 40° and 
30°, between which limits, when vibrating alone, it completed 
exactly 100 vibrations; and when caused to vibrate about the 
magnet, it completed 55 vibrations with the lesser tension, and 
88 vibrations when the tension was doubled. In this instance, 
the respective forces deduced by the formula, correspond as nearly 
as could be expected with the previously observed attraction on 
the iron. 
This method of detecting changes in the magnetic force of a 
bar, seems therefore susceptible of precision. It is besides ex- 
tremely delicate ; the only apparent objection is the great accu- 
racy in manipulation requisite for its perfect success. It is never- 
theless available at any time, and in any place, since the vibra- 
tions of the copper-ring alone, taken within certain limits, may 
be always reduced to a constant and given number. 
31. The experiments of Moricury1 and Mrs SomeRvILLe 
seem to shew, that certain magnetic properties exist in the solar 
