Page:Collected Physical Papers.djvu/259

Rh It will be observed that under the above condition also, there is a continuous diminution of resistance with an increase of E. M. F.

Time-lag

The changes which give rise to the conductivity variation take a short time for their completion. The curves were taken when the electromotive variation was produced at a moderate and uniform speed. But if the electromotive variation is produced quickly and step by step, each step being followed by a pause, then

there is an immediate effect, followed by a permanent effect, the galvanometer deflection creeping up to this permanent value. This creeping effect becomes more marked with higher E. M. F. I give above a record where this effect is shown (fig. 53). The vertical