Page:On Electric Touch and the Molecular Changes produced in Matter by Electric Waves.djvu/16

Rh The curve given in fig. 3 clearly exhibits the reversals. This curve also explains the behaviour of magnesium noticed in my last paper, which appeared very curious at the time. "It is sometimes possible to so adjust matters that one flash of radiation produces a diminution of resistance, and the very next flash an increase of resistance. Thus a series of flashes may be made to produce alternate throws of the galvanometer needle."

The receiver was so adjusted as to give a deflection of five divisions.

The first flash of radiation produced an increased deflection of 90 divisions (magnesium having a positive electric touch); the second flash produced a further deflection of five divisions, the third flash produced a negative deflection of five divisions, the fourth flash produced + 5, the fifth flash gave - 90 divisions, and the sixth flash a deflection of + 90. The reversals followed each other almost regularly, till the substance became insensitive.

III. Lastly, we may have a class of substances where the conversion from one state to the other is not complete. Here, again, We get two sub-divisions, owing to the distinction between positive and negative substances.

Taking first the case of a positive substance (see fig. 4 (β)), the original conductivity of which is represented by a, the action of the first few flashes of radiation would be to produce a great increase of conductivity by the formation of B variety; the next flashes convert