24 



THE CUBA REVIEW. 



PROTECTION FROM LIGHTNING. 



An Inexpensive System — Size of Wire Required — How to Place Wires and 

 Rods — Proper Connections With the Earth — Wire Fence Protection. 



(Condensed from Farmers' Bulletin Xo. 367, issued by the U. S. Department of Agriculture.) 



A paper entitled Lightning and Light- 

 ning Conductors, by Alfred J. Henry, Pro- 

 fessor of Meteorology, which suggests 

 means of protection froin destructive 

 lightning strokes, has been published 

 by the U. S. Department of Agriculture. 

 His instructions, which follow, will en- 

 able anyone to erect comparatively in- 

 expensive yet efifective lightning con- 

 ductors. The instructions are for a build- 

 ing on which there is neither cupola nor 

 chimney, as is shown in figure 1. 



The Materials Required 



are No. 3 or No. 4 double galvanized iron 

 telegraph wire, about one pound of galvan- 

 ized iron staples, some connecting tees, and 

 one pound of aluminum paint. While iron 

 is not so good a conductor as copper it is 

 less likely to cause dangerous side flashes, 

 and it is cheaper. 



Experiments by experts have tended to 

 demonstrate that iron is in many situations 

 a very useful material for lightning rods, 

 as the effective energy of a flash of light- 

 ning is rapidly dissipated in iron, but the 



Fig. 1.— Method of placing lightning rods on a building having 

 no cupola or chimney. Length of building, about 25 feet. 

 FIGURE I. 



La figura i muestra un edificio de 25 pies de 

 largo protegido de las descargas electricas por 

 medio de pararrayos. Para un edificio de esta 

 clase, et alambre galvanizado No. 3 es suficiente ; 

 para un edificio de 56 pies de largo se requiere 

 el alambre No. 4. En esta figura se muestra un 

 alambre extendido a todo lo largo del tejado, con 

 una inclinacion de 20 pulgadas a cada lado, con 

 otro alambre del mismo tamafio en el centro. Las 

 conexiones, segun se muestra, estan colocadas a 

 cada lado del tejado y los extremos entran en 

 el terreno. Esta es la manera de colocar los 

 alambres en un edificio sin cupula 6 chimenea. 



FIGURE 2. 



La figura 2 muestra la clase de empalmes gal- 

 vanizados que se usan para afianzar el alambre 

 al edificio. 



wire must be galvanized or even doubly 

 galvanized. The ordinary telegraph wire 

 has a diameter of about fifteen one-hun- 

 dredths of an inch, it is often struck by 

 lightning, yet it is seldom fused. It is 

 probable that although a light iron wire may 

 be melted it will have served its purpose 

 before being destroyed. No. 3 wire is about 

 twice the size of telegraph wire (No. 9), 

 and the writer does not know of a case 

 wherein that size has been fused by a light- 

 ning discharge, and therefore feels no hesi- 

 tancy in recommending its use as a light- 

 ning conductor for isolated buildings of 

 moderate height. 



The T connections are shown in figure 2. 

 They should be galvanized. 



Directions for Putting Up Wires, 



The conducting system is composed of a 

 horizontal wire following the ridge of the 

 roof, and two vertical wires connecting with 

 the ground on both sides of the building. 

 (See illustration No. 1.) The wires should 

 be fastened to the building by galvanized 

 iron staples about an inch long, or by means 

 of small wooden blocks with screw eyes, 10 

 feet apart. The wire can be easily passed 

 through these eyes from the ground to the 

 top of the building. 



The vertical rods should be connected to 

 the horizontal wire by galvanized iron tees 

 (figure 2). The necessary tees should be 

 slipped on to the horizontal wire and placed 

 at points of junction with the downward 

 directed wires and also at points where it 

 is wished to erect short terminal rods along 

 the ridge of the roof. 



Three terminals of rods are shown in 

 figure 1, and these need not be more than 

 20 inches long. Make the end terminals a 

 right angle bend in the wire which runs 

 along the ridge of the roof at a distance of 

 20 inches from the respective ends. The 



