Page:Collected Physical Papers.djvu/174

154 Fig. 27 exhibits the actual curve obtained with a (compound) positive substance.

It is remarkable for its regularity. The next figure (fig. 28) gives the curve for iron. The first diminution of resistance is too great to be properly represented in the diagram. Here we have the same type as in the previous case; the inert stage, b, is also more conducting than a; (compare with ﬁg. 26 β).

IV. I will now consider the case of a negative substance exhibiting damping; arsenic will be taken as an example where the damping is not so great as in the. case of iron. Fig. 29 represents the actual curve obtained with arsenic (compare with the hypothetical curve for a negative substance, fig. 26α). It will be observed that the negative substance in the fatigued state is, on the whale, less conducting than in the fresh condition, as we were led to expect from the hypothetical curve.

It will also be seen that the oscillations are fairly regular towards the end. The curves given in figs. 28 and 29 are those obtained with specimens immediately after they were set up. Had I given them a period of rest to allow the particles to get properly