Until Trouve's trip on the Seine, in 1881, and the launch of the
Electricity on the Thames, in 1882, very little was known concerning the
history of electric navigation.

M. Trouve originally employed Plante's secondary battery, but afterward
reverted to a bichromate battery of his own invention. In all the
primary batteries hitherto applied with advantage, zinc has been used as
the acting material. Where much power is required, the consumption of
zinc amounts to a formidable item; it costs, in quantity, about 3d. per
pound, and in a well arranged battery a definite quantity of zinc is
transformed. The final effect of this transformation manifests itself in
electrical energy, amounting to about 746 watts, or one electrical horse
power for every two pounds of this metal consumed per hour. The cost of
the exciting fluid varies, however, considerably; it may be a solution
of salts, or it may be dilute acid. Considering the zinc by itself, the
expense for five electrical or four mechanical horse power through an
efficient motor, in a small launch, would be 2s. 6d. per hour. Many
persons would willingly sacrifice 2s. 6d per hour for the convenience,
but a great item connected with the employment of zinc batteries is
in the exciting fluid, and the trouble of preparing the zinc plates
frequently. The process of cleaning, amalgamating and refilling is so
tedious, that the use of primary batteries for locomotive purposes is
extremely limited. To recharge a Bunsen, Grove, or bichromate battery,
capable of giving six or seven hours' work at the rate of five
electrical horse power, would involve a good day's work for one man; no
doubt he would consider himself entitled to a full day's wages, with the
best appliances to assist him in the operation.

Several improved primary batteries have recently been brought out, which
promise economical results. If the residual compound of zinc can be