n (910. 917. 973.). For as the whole result depends upon the
opposition of forces at the places of electric excitement and
electro-decomposition, and as water is the substance to be decomposed at
both before the current can move, it is not to be expected that the zinc
should have such powerful attraction for the oxygen, as not only to be able
to take it from its associated hydrogen, but leave such a surplus of force
as, passing to the second place of decomposition, should be there able to
effect a second separation of the elements of water. Such an effect would
require that the force of attraction between zinc and oxygen should under
the circumstances be _at least_ twice as great as the force of attraction
between the oxygen and hydrogen.

1012. When two pairs of zinc and platina exciting plates were used, the
current was also practically stopped by one interposed platina plate, fig.
93. There was a very feeble effect of a current at first, but it ceased
almost immediately. It will be referred to, with many other similar
effects, hereafter (1017.).

1013. Three pairs of zinc and platina plates, fig. 94, were able to produce
a current which could pass an interposed platina plate, and effect the
electrolyzation of water in cell iv. The current was evident, both by the
continued deflection of the galvanometer, and the production of bubbles of
oxygen and hydrogen at the electrodes in cell iv. Hence the accumulated
surplus force of three plates of zinc, which are active in decomposing
water, is more than equal, when added together, to the force with which
oxygen and hydrogen are combined in water, and is sufficient to cause the
separation of these elements from each other.

1014. The three pairs of zinc and platina plates were now opposed by two
intervening platina plates, fig. 95. In this case the current was stopped.

1015. Four pairs of zinc and platina plates were also neutralized by two
interposed platina plates, fig. 96.

1016. Five pairs of zinc and platina, with two interposed platina plates,
fig. 97, gave a feeble current; there was permanent deflection at the
galvanometer, and decomposition in the cells vi and vii. But the current
was very feeble; very much less than when all the intermediate plates were
removed and the two extreme ones only retained: for when they were placed
six inches asunder in one cell, they gave a powerful current. Hence five
exciting pairs, with two interposed obstructing plates, do not g