612. Why should conductors have at their base several branches penetrating the earth?
To facilitate the discharge of the accumulated electricity into the earth.
613. Why does electricity affect the shapes of clouds?
Because electricity does not penetrate the masses of bodies, but affects generally their surfaces. Hence electricity exists in the surfaces of clouds, and in its efforts to find an equilibrium it causes the clouds to roll in heavy masses, having dark outlines.
"All ye inhabitants of the world, and dwellers on the earth, see ye, when he lifteth up an ensign on the mountains; and when he bloweth a trumpet, hear ye."—Isaiah xviii.
The fact that electricity resides in, and is conducted by, the surfaces of bodies, is well established, and should receive due attention in the protective measures adopted to secure life and property against the effects of lightning. A practical suggestion that arises out of this fact is, that tubes of copper would form far more efficient conductors than bars of the same metal. A copper tube, of half an inch diameter, would conduct nearly double the amount of electricity which could be conveyed away by a bar of copper of the same diameter. The upper extremity of the tube should be open obliquely, that the electric current might be induced to pass over both the inner and outer surfaces.