Page:Proceedings of the Royal Society of London Vol 4.djvu/73

Rh quired during the previous polarization. The lines of inductive ac- tion which occur in fluid electrolytes are exemplified by employing for that purpose clean rectified oil of turpentine, containing a few- minute fibres of very clean dry white silk; for when the voltaic circuit is made by the introduction into the fluid of wires, passing through glass tubes, the particles of silk are seen to gather together from all parts, and to form bands of considerable tenacity, extending between the ends of the wires, and presenting a striking analogy to the arrangement and adhesion of the particles of iron filings between the poles of a horse-shoe magnet.

The fact that water acquires greater power of electrolytic induc- tion by the addition of sulphuric acid, which not being itself decom- posed, can act only by giving increased facility of conduction, is ad- duced as confirming the views of the author.

The phenomena of the disruptive electric discharge are next ex- amined with reference to this theory : the series of inductive actions which invariably precede it are minutely investigated : and reference is made to the accurate results obtained by Mr. Harris, as to the law of relation between the intensity of a charge, and the distance at which a discharge takes place through the air.

The theory of Biot and others, which ascribes the retention of a charge of electricity in an insulated body to the pressure of the sur- rounding atmosphere, is shown to be inconsistent with various phe- nomena, which are readily explained by the theory adopted by the author.

The author then enters into an inquiry relative to the specific con- ducting capacities of difi^erent dielectrics.

With a view of determining the degrees of resistance to the transit of electricity excited by difl'erent kinds of gases, he constructed an apparatus, in which an electric discharge could be made along either of two separate channels ; the one passing through a receiver filled with the gas, which was to be the subject of experiment, and the other having atmospheric air interposed. By varying the length of the passage through the latter, until it was found that the discharge occurred with equal facility through either channel, a measure was aflfbrded of the relative resistances in those two lines of transit, and a determination consequently obtained of the specific insulating power of the gas employed.

The circumstances attending the diversified forms of the disruptive discharge, such as the vivid flash or spark, the brush or pencil of light, and the lucid point or star, which severally represent diff'erent conditions of the sudden transit of electrical forces through an inter- vening dielectric, are minutely investigated in their various modifi- cations. The spark is the discharge, or reduction of the polarized inductive state of many dielectric particles, by the particular action of a few of those particles occupying but a small and limited space, leaving the others to return to their original or normal condition in the inverse order in which they had become polarized : and its path is determined by the superior tension which certain particles have ac- quired, compared with others, and along which the action is accord-