engine), and the corresponding consumption of the elements of the
battery: Attached to the spindle of the machine was a small pulley, Q
Q (Fig. 3), for the purpose of driving, by means of a cord, another
pulley on a horizontal spindle carrying a drum on which was wound a
cord carrying a weight, and on the same spindle was also a brake and
brake-wheel, the lever of which was loaded so as just to prevent the
weight setting into motion the whole system, consisting of the two
machines, when no current was flowing. In this condition, when the
machine was set in motion by connecting the battery, the mechanical
work expended in overcoming the friction of the brake was equal to
that required to raise the weight; and, in order to obtain the total
work done, all that was necessary was to multiply the weight lifted by
the distance through which it was raised. The consumption of the
battery was estimated at the same time by interposing in the circuit a
sulphate of copper voltameter, of which the copper plate was weighed
before and after the experiment. The following are some of the results
obtained by Dr. Pacinotti in experimenting after the manner just
described. With the current from a battery of four small Bunsen
elements, the machine raised a weight of 3.2812 kilos to a height of
8.66 m. (allowing for friction), so that the mechanical work was
represented by 28.45 m. During the experiment the positive plate of
the voltameter lost in weight 0.224 gramme, the negative gaining 0.235
gramme, giving an average of chemical work performed in the voltameter
of 0.229 gramme, and multiplying this figure by the ratio between the
equivalent of zinc to that of copper, and by the number of the
elements of the battery, the weight of zinc consumed in the battery
was computed at 0.951 gramme, so that to produce one kilogrammeter of
mechanical work 33 milligrammes of zinc would be consumed in the
battery. In another experiment, made with five elements, the
consumption of zinc was found to be 36 milligrammes for every