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 explained by supposing that small plates give a small quantity of the electric fluid with a high velocity, while large plates give a larger quantity with 10 greater velocity. Shocks, which were supposed to depend on the velocity of the fluid alone, would therefore not be intensified by increasing the size of the plates.

The effect of varying the conductors which connect the terminals of the pile was also studied. Nicolas Gautherot (b. 1753, d. 1803) observed that water contained in tubes which have a narrow opening does not conduct voltaic currents so well as when the opening is more considerable. This experiment is evidently very similar to that which Beccaria had performed half a century previously with electrostatic discharges.

As we have already seen, Cavendish investigated very completely the power of metals to conduct electrostatic discharges; their power of conducting voltaic currents was now examined by Davy. His method was to connect the terminals of a voltaic battery by a path containing water (which it decomposed), and also by an alternative path consisting of the metallic wire under examination. When the length of the wire was less than a certain quantity, tho water ceased to be decomposed; Davy measured the lengths and weights of wires of different materials and cross-sections under these limiting circumstances; and, by comparing them, showed that the conducting power of a wire formed of any one metal His inversely proportional to its length and directly proportional to its sectional area, but independent of the shape of the crosssection. The latter fact, as he remarked, showed that voltaic currents pass through the substance of the conductor and not along its surface.

Davy, in the same memoir, compared the conductivities of various metals, and studied the effect of temperature: he found