Excerpt from Recent Practice in the Erection of Lightning Conductors

So it is exactly with the store of energy beneath an electrified cloud or be tween one cloud and another. A lightning conductor of perfect conductivity, it struck, would deal with the energy in far too rapid and sudden a manner, and the result would be equivalent to an explosion. A conductor of moderately high resistance, such as an iron wire, would get rid of it in a slower and there fore much safer and quieter manner, though with too thin a wire there may be risk of fire.

The rush in any case, however, is likely to be rather violent, and, like an avalanche. It will not take the easiest path provided for it. As if it were a trickling stream, but will crash through obstacles and make its own path, some portions of it taking paths which would be quite unexpected. Hence, no one path can be said to protect others, and the only way to protect a building with absolute completeness is to inclose it wholly in metal. An invisible cage or framework of iron wires, however, descending vertically down its salient fea tures, with the utilization of any metal in its construction, suffices for all practical purposes, unless the building is a powder magazine.

The effect of points, and of rain also. In gradually dissipating a charge. And thereby contributing to safety. Has long been understood; but the feature which has not been known is that there are cases where points are wholly inoperative, viz, when the energy is stored between cloud and cloud. Instead of between cloud and earth. And when the initial discharge takes place from one cloud to another; then the lower cloud is liable suddenly to overflow to earth through a region in which there was no previous preparation, and where any number of points. Or a rain shower, or any other form of gentle leak, would have been quite inoperative. Then can a violent discharge occur to even the sharpest point; and a hot column of air, such as rises up a chimney, is even preferred to a conductor. These are the flashes against which points and rain are no protection, and these are prob ably those which do the most damage to protected buildings. But it must be understood that when a flash does occur through a building. It matters little which kind of flash it is - both can be equally sudden and violent - but if the building is well provided with points, the first or prepared kind is not likely to occur, save in exceptional cases; the dangerous liability is then the sudden or overflow variety of flash.

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