Page:Popular Science Monthly Volume 43.djvu/470

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45^ THE POPULAR SCIENCE MONTHLY.

calm enjoyment of the belief that rods did protect. The Light- ning-rod Conference had shown, in quite an exhaustive report, that Faraday's position (as opposed to the opinions of Harris) was correct, viz., that the problem was one of simi)le conductiv- ity ; that a solid rod was better than a tube or tape (which would give greater surface with less copper) ; that solid volume was everything, superficial area nothing ; and that, provided the me- tallic passage afforded the Hash was continuous, any Hash might be successfully carried off and harmlessly conducted to the ground.

This conference, while not strictly an oflicial body, was one that, from the character of its members, carried great weight. It was a joint committee of representative members of the Institute of British Architects, the Physical Society, the Society of Tele- graph Engineers and Electricians, the Meteorological Society, and two co-opted members.

In 1888 came Dr. Oliver J. Lodge's remarkable course of lectures before the Society of Arts upon the oscillatory character of the lightning flash.. Then followed the famous dicussion at the meeting of the British Association. As this debate was one in which quarter was neither asked nor given, and the ques- tion at issue was clearly understood by all to be whether a light- ning conductor, when constructed in accordance with the direc- tions of the conference, would absolutely protect, it may not be out of place to give here a synopsis of the arguments advanced. Mr. Preece, who opened the discussion, defined the functions of a lightning conductor as twofold. " It facilitates the discharge of the electricity to the earth, so as to carry it off harmlessly, and it tends to prevent disruptive discharges by silently neutralizing the conditions which determine such discharges in the neighbor- hood of the conductor. To effect the first object, a lightning con- ductor should offer a line of discharge more nearly perfect and more accessible than any other ottered by the materials or con- tents of the edifice we wish to protect. To effect the second ol)- ject, the conductor should be surmounted by a point or points ; fine points and flames have the projjerty of slowly and silently dissipating the electrical charges; they, in fact, act as safety valves. If all those conditions be fulfilled, if the points be higli enough to be the most salient features of the building, no mat- ter from what direction the storm cloud may come, be of ample dimensions and in thoroughly perfect electrical connection with the earth, the edifice, with all that it contains, will be safe, and the conductor might even be surrounded by gunpowder in the heavi- est storm without risk of danger. All accidents may be said to be due to a neglect of tliese simple eleiuentary principles. The most frequent sources of failure are conductors deficient either in

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