Page:Popular Science Monthly Volume 88.djvu/151

 For Practical Workers

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���A Radium Lightning Rod

By Lucien Fournier

A LIGHTNING ROD does not pre- vent the occurrence of lightning". It even provokes it, but suppresses its incendiary effects. Such, indeed, is its chief object.

May we not increase its efficacy in this direction? The problem is an in- teresting one. We know that if the air were a very good con- ductor of electricity there would be no electrical storm. All that is neces- sary for our purpose, therefore, is to give the air this quality artificially.

Nothing is more simple — we need only to ionize it. To ionize the air is, so to speak, to "metallize" it by means of infinitesi- mal particles like those which are given off by radium and which are discharged into the sur- rounding space from the point of emission. From the recognition of this fact to the construction of a radium lightning rod

was only a step. Its con- a radium lightning rod which Struction is not diflicult ; depends on the ionization of it is only necessary to ^^^ ^i"" fo^ efficacy

put a few milligrams of radium on a plate, installed on a lightning rod near its terminal. The inventor of the process has constructed an experiment- al rod consisting of three brass tubes fitting into one another and having a total length of about 12 feet. The tubes

���are mounted on a massive support of

��ebonite, restmg on a cast iron base fixed in the ground. At the summit of the apparatus is a cluster of three points, and below them the plate con- taining the radio-active substance. This plate, slightly convex upward, is of copper, about one-tenth of an inch thick and ten inches in diameter. The radio-active substance is spread in the form of a ring on its upper surface, the ring being about three- quarters of an inch in breadth and concentric with the edge of the plate. The amount of radium is only 0.2 milligramme (about .003 grain), and it is deposited on the plate by electrolysis.

What effects are pro- duced by this small amount of radio-active substance upon the sur- rounding air? The in- ventor declares that the conductivity of the air is increased several million- fold, and that this con- ductivity extends to a con- siderable distance from the point of emission, \ iz., the terminal of the lightning conductor. Under these conditions the passage of electricity will take place between earth and air. not by brus(|ue, irregular discharges, limited to a single point, but by a constant, steady current passing through a column of air hriving a radius of thirty or forty feet. The pro- gressive conductivity of the air toward the terminal concentrates the flow of

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