hydrogen is 158 liters per hour.

It is clear that, in an industrial exploitation, a dynamo working
under 3 volts is never employed. In order to properly utilize the
power of the dynamo, several voltameters will be put in series--a
dozen, for example, if the generating machine is in proximity to the
apparatus, or a larger number if the voltameters are actuated by a
dynamo situated at a distance, say in the vicinity of a waterfall.
Fig. 3 will give an idea of a plant for the electrolysis of water.

It remains for us to say a few words as to the net cost of the
hydrogen and oxygen gases produced by the process that we have just
described. We may estimate the value of a voltameter at a hundred
francs. If the apparatus operates without appreciable wear, the
amortizement should be calculated at a very low figure, say 10 per
cent., which is large. In continuous operation it would produce more
than 1,500 cubic meters of gas a year, say a little less than one
centime per cubic meter. The caustic soda is constantly recuperated
and is never destroyed. The sole product that disappears is the
distilled water. Now one cubic meter of water produces more than 2,000
cubic meters of gas. The expense in water, then, does not amount to a
centime per cubic meter. The great factor of the expense resides in
the electric energy. The cost of surveillance will be minimum and the
general expenses _ad libitum_.

Let us take the case in which the energy has to be borrowed from a
steam engine. Supposing very small losses in the dynamo and piping, we
may count upon a production of one cubic meter of hydrogen and 500
cubic decimeters of oxygen for 10 horse-power taken upon the main
shaft, say an expenditure of 10 kilogrammes of coal or of about 25