RECOLLECTIONS AND REFLECTIONS
causes which it was very difficult to locate. We know now that these two phenomena are the most complex and difficult in the whole range included in the subject of conduction of electricity through gases. To have come upon a method of producing conductivity in the gas so controllable and so convenient as that of the X-rays was like coming into smooth water after long buffeting by heavy seas. The X-rays seem to turn the gas into a gaseous electrolyte. Indeed, many of the difficulties which had been met with in the early stages of the conduction through liquid electrolytes had been met with in those of the conduction through gases. One of these difficulties in the case of liquid electrolytes was to see how the positively and negatively charged atoms in a molecule of the electrolyte could be separated from each other by the very small electric forces which are adequate to produce conduction. The attraction between these oppositely charged atoms is of the order of 1,600,000,000 volts per cm., and yet a force of a fraction of a volt per centimetre is sufficient to make an atom with a positive charge appear at one electrode and one with a negative charge at the other. To explain this Grotthus, in 1805, introduced the idea that the molecules with their + and - atoms formed themselves into chains, like iron filings when acted upon by a magnet and that the -f- atom in one molecule went close to the - atom of the adjacent molecule in the way indicated in the figure. AB, CD, EF represent molecules.
The attraction of the positive charge of B on the atom A is balanced by the repulsion due to the negative charge on C, which is close to B. Each atom, except those at the end, has a close neighbour of opposite sign, so that the two 326