WITH THE CAVENDISH APPARATUS. 
221 
It is true that results tolerably accordant on the whole are deduced in this manner, 
but there is no explanation why they should be so combined. It may be regarded 
as a mode of combination of the experimental data so arranged as to allow a medium 
result to emerge, in spite of the immense discrepancies which he could not but have 
perceived would have appeared had results been deduced from every pair of successive 
experiments. I must not here be understood as insinuating any kind of deception 
on the part of this great experimental philosopher ; on the contrary, he is candid in 
the extreme. He frequently refers to the “variation in the time of vibration and the 
perturbation of the resting points” as things for which he cannot account, and some- 
times says, “ there must be some disturbing force.” Also “ the force of torsion must 
be subject to variation.” With respect to the hypothesis of a change in the torsion 
force, though I might grant its possibility when a single wire is employed for the 
suspending line, I cannot grant it when bifilar silk lines are used. In this case the 
force of torsion is easily calculated, and there is no reason why it should at all change. 
But when such lines, * 1 77 inch apart, are used, the greatest anomalies occur; and I 
am persuaded that if the distance were still further diminished, and the torsion force 
thereby rendered weaker, the anomalies would be still further increased. 
In order to obtain a theory which would account for the anomalies I tried many 
plans. One was the integration of the equation of motion (including resistance) to 
terms of the second order, but the corrections thence arising were far too minute to 
afford any explanation. Besides the above reason against the alteration of the torsion 
force, another occurred to me, which was this, — were a change in the torsion force 
the sole cause of the perturbations, the time and resting point ought always to change 
simultaneously , but this is observed not to be the case. Examples in abundance will 
present themselves to any one consulting the tables, in which the time changes, and 
the resting point remains nearly unaltered, and vice versa. Heat also was out of the 
question, in consequence of the extreme precautions used to prevent the intrusion of 
this sort of disturbance. 
At length I determined to try the effect of a supposed magnetic state of the masses 
and balls, and, as will be seen in the sequel, the hypothesis succeeded beyond my 
most sanguine expectations. It is strongly suspected that all bodies are more or less 
susceptible of the magnetic state, and I think it very probable that what is called the 
coercive power of a substance, or that power which it possesses of retaining its mag- 
netic state, after the magnetizing power has been withdrawn, for a longer or shorter 
period, may not only differ for different substances, which we know it does, but for 
different intensities of magnetization. Thus, if magnetism be induced by a powerful 
magnet in a mass of soft iron or lead, the magnetic state will, to all appearance, 
subside when the magnet is withdrawn, and that very rapidly, perhaps instantaneously. 
Now I contend that such may not be the case if the magnetization were very small ; 
it may require, even in lead, some time to elapse before the very feeble magnetic state 
wholly subsides. 
