52 Faraday's Researches

opposite the litmus paper; the negative point n opposite the
turmeric. The machine was then worked for a time, upon
which evidence of decomposition quickly appeared, for the
point of the litmus b became reddened from acid evolved there,

Fig. 10.

and the point of the turmeric a red from a similar and simul-
taneous evolution of alkali.

202. Upon turning the paper conductor round, so that the
litmus point should now give off the positive electricity, and
the turmeric point receive it, and working the machine for a
short time, both the red spots disappeared, and as on continu-
ing the action of the machine no red spot was re-formed at the
litmus extremity, it proved that in the first instance (199) the
effect was not due to the action of brushes or mere electric dis-
charges causing the formation of nitric acid from the air (58).

203. If the combined litmus and turmeric paper in this ex-
periment be considered as constituting a conductor independent
of the machine or the discharging train, and the final places
of the elements evolved be considered in relation to this con-
ductor, then it will be found that the acid collects at the
negative or receiving end or pole of the arrangement, and the
alkali at the positive or delivering extremity.

204. Similar litmus and turmeric paper points were now
placed upon glass plates, and connected by a string six feet
long, both string and paper being moistened in solution of
sulphate of soda; a needle point connected with the machine
was brought opposite the litmus paper point, and another
needle point connected with the discharging train brought
opposite the turmeric paper. On working the machine, acid
appeared on the litmus, and alkali on the turmeric paper; but
the latter was not so abundant as in former cases, for much of
the electricity passed off from the string into the air, and
diminished the quantity discharged at the turmeric point.ts were repeated with