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regard to such bodies as glass, resins, and above all, gases, it 
seems impossible that currents of electricity capable of pro- 
ducing these effects should be generated in them, yet Arago 
found that the effects in question were produced by these and 
by all bodies tried. Messrs. Babbage and Herschel, it is true, 
did not observe them with any substance not metallic, except 
carbon in a highly conducting state. Mr. Harris has ascer- 
tained their occurrence with wood, marble, freestone, and 
annealed glass, but obtained no effect with sulphuric acid 
and saturated solution of sulphate of iron, although these are 
better conductors of electricity than the former substances. 
" Future investigations will no doubt explain these difficulties, 
and decide the point whether the retarding or dragging 
action spoken of, is always simultaneous with electric cur- 
rents." 
We thus know that when a body revolves it induces a 
motion in another body. We know not what to term the 
power or force thus induced or produced, we know not at 
what distance this force would be felt if the force itself 
became more powerful, or if the bodies could be insulated in 
space, but it is not unreasonable to conclude that the distance 
might be considerably increased. It has been shown that it 
is not necessary that the bodies should be metallic, or even 
conductors of electricity, to be influenced by this motion. 
But we know that when both bodies are at rest, then no 
effect is produced by the one upon the other. When, then, 
we find that the sun rotates upon its axis, and that the earth 
also rotates and in the same direction ; that all the planets 
rotate just as does the earth, and that the direction of the motion 
is uniform, it is difficult to avoid comparing this movement to 
that of the various bodies suspended around the magnet, the 
rotation of which causes an exactly similar movement in them. 
From experiments of my own I am induced to believe 
that the velocity of rotation induced by a magnet in any 
