A very pretty and instructive experiment may be performed by arranging the apparatus as shown in Fig. 10, with the copper strips, H H, inserted in clean water and the galvanometer placed in the circuit. The deflection of the galvanometer needle will be very slight, showing that the resistance of clean water is considerable. A few drops of sulphuric acid or even vinegar will increase the conductivity of the water so as to produce a marked deflection of the galvanometer needle.

FIG. 10. - RESISTANCE OF FLUIDS.

Common salt added to the water will produce the same effect.