tructed. It will be especially needful in such experiments, to
describe the nature of the electrodes used, or, if possible, to select such
as, like platina or plumbago in certain cases, shall have no power of
assisting the separation of the _ions_ to be evolved (913).

987. Of the two modes in which bodies can transmit the electric forces,
namely, that which is so characteristically exhibited by the metals, and
usually called conduction, and that in which it is accompanied by
decomposition, the first appears common to all bodies, although it occurs
with almost infinite degrees of difference; the second is at present
distinctive of the electrolytes. It is, however, just possible that it may
hereafter be extended to the metals; for their power of conducting without
decomposition may, perhaps justly, be ascribed to their requiring a very
high electrolytic intensity for their decomposition.

987-1/2. The establishment of the principle that a certain electrolytic
intensity is necessary before decomposition can be effected, is of great
importance to all those considerations which arise regarding the probable
effects of weak currents, such for instance as those produced by natural
thermo-electricity, or natural voltaic arrangements in the earth. For to
produce an effect of decomposition or of combination, a current must not
only exist, but have a certain intensity before it can overcome the
quiescent affinities opposed to it, otherwise it will be conducted,
producing no permanent chemical effects. On the other hand, the principles
are also now evident by which an opposing action can be so weakened by the
juxtaposition of bodies not having quite affinity enough to cause direct
action between them (913.), that a very weak current shall be able to raise
the sum of actions sufficiently high, and cause chemical changes to occur.

988. In concluding this division _on the intensity necessary for
electrolyzation_, I cannot resist pointing out the following remarkable
conclusion in relation to intensity generally. It would appear that when a
voltaic current is produced, having a certain intensity, dependent upon the
strength of the chemical affinities by which that current is excited
(916.), it can decompose a particular electrolyte without relation to the
quantity of electricity passed, the _intensity_ deciding whether the
electrolyte shall give way or not. If that conclusion be confirmed, then we
may arrange circumstances so that the