Page:Proceedings of the Royal Society of London Vol 69.djvu/418

400 the buttons faced round, always presenting the blue face to the- negative pole. Examination with a spectroscope showed strong hydrogen lines in the pink parts, and both hydrogen and mercury in the blue parts. Fig. 1 shows the appearance at this stage.

Fig. 1.

The exhaustion was now raised to 2 mm., when the whole of the blue faces of the parti-coloured buttons suddenly migrated to one bright blue, Avell-formed button, nearest the negative pole, all the other buttons remaining pink. The appearance is shown in fig. 2.

FIG. 2.

Round the negative pole an indistinct halo showed both mercury and hydrogen ; but on the blue button mercury only was detected, not a trace of even the brightest hydrogen line being there seen. On the pink portions the hydrogen lines were in excess, but mercury could be seen all along the tube.*

constituents of the strata into one single button at the end near the negative pole. In the classical researches of Messrs. De la Hue and H. W. Mliller on the 'Electric Discharge with the Chloride of Silver Battery,' numerous references are made to the blue and pink parti-coloured character of the strata, and also to the change of colour from all blue to all pink which follows a change in the electrical condition?. Thus we read : " Thirty-nine strata, the convex side being blue and the broader concave side reddish." " Twenty-one strata, very blue on the convex face, pink on the concave." ' Phil. Trans.,' vol. 169, p. 175.
 * I hare been unable to find any reference to this concentration of the blue

Sometimes the stratifications are described as all of one colour : " Twenty-one very blue strata." " The strata were blue, and sixty-one in number." " Showing