Yet we have no other evidence of any repulsive force at all being exerted by the sun,--at least no evidence which can be regarded as demonstrative,--and still less have we any evidence of a repulsive force exceeding in energy the sun's attracting power." (Proctor.) CHAPTER IX. INTERPRETATION OF COMETIC PHENOMENA. Now, curiously enough, we have in constant use in our laboratories a little instrument called the electroscope, in which we have manifested very clearly a repulsive force exceeding in energy the earth's attracting power, and very greatly exceeding it. It is described in "Electricity in the Service of Man" as follows: "If we rub a large glass rod with a silk pad, we observe that it will attract light bodies, then, after contact, repel them. During the process we may notice a peculiar noise, and if the experiment be carried out in the dark we may further notice sparks passing between the rod and the rubber, and also that the rod becomes luminous. If we suspend a pith-ball by means of a silk thread, on bringing the rubbed rod near the pith-ball it will move towards the rod, touch it, and then be repelled. If the glass rod be again brought near the pith-ball, it will move away from the glass rod, and continue to be repelled until it has been touched by some other body.... In order to ascertain whether electricity is communicated by electrified bodies to non-electrified bodies when brought into contact, let us suspend two pith-balls from the same point of support by threads of uniform silk, and touch the pith-balls with the rubbed glass rod. The balls fly from the rod and also from one another. On bringing near them a third pith-ball or any other light body, we find that, though they repel one another, they are attracted by the light body, showing that they have become electrified by contact with the rubbed glass rod. From this we conclude that an unelectrified body may be electrified by contact with an electrified body, and also that there is repulsion after contact. There is mutual repulsion between two electrified bodies, but there is attraction between a single electrified body and one that is unelectrified." The mutual repulsion of these pith-balls is the exact measure of the strength of electrification. Hung side by side to the knob of a prime conductor of an electrical machine, the mutual repulsion of the similar electrospheres of these pith-balls drives them apart against the earth's gravity and holds them extended, if the electrical tension be sufficient, to their widest limit of divergence. It is, in effect, precisely similar to the action of the solar and cometic electrospheres (see illustration in a previous chapter, page 124), each being similarly electrified and communicating with the other across a space which, as before stated, is freely traversable by electric currents without appreciable resistance. That such electrospheres are flaming with heat does not interfere with such self-repellent action; in fact,