33 



As the cables near the ground are often subject to injury by stock, implements, 

 etc., they should be protected by wooden strips fastened together in suitable form 

 and nailed over the cable from the ground up to a height of six or eight feet. 



No Insulators to Be Used. 



4. Attachment. — Insulators should not he used. The rods should be in metal- 

 lie connection with the building. This method of attachment is in direct oppo- 

 sition to that practised when lightning rods were first used. It was then considered 

 desirable to insulate the rods' from the huilding by glass or earthenware insulators. 

 As a thunderstorm approaches the entire outer surface of the building is charged 

 with electricity, and by having the rods in metallic connection with the building 

 the charge is conducted to the rods and thence to the points where it leaks off and 

 neutralizes the opposite charge existing in the cloud. 



Several methods are used for fastening the cable to the building. Some com- 

 panies use copper nails, which are driven right through the cable. Others use 

 staples, others clips which hold the cable tight to the building, and some use a 

 clip which holds the cable out about an inch from the building, the claim for the 

 last method being that with the rod standing out chaff, straw, and the like would 

 not so readily collect between the rod and building, and thus a danger of fire is 

 avoided in case strokes occur. At first the writer rather thought this point well 

 taken, but after finding an efficiency of 999 cases out of 1,000 in Michigan where 

 the rods were practically all fastened close to the building, and the three small 

 damages that did occur all being due to other causes, we concluded that it would be 

 rather difficult to secure any higher efficiency. While we say this, we see no par- 

 ticular objection to having the rods stand out from the building, unless it might be 

 that the rod is more exposed and thus more subject to injury. 



Points Twenty to Thirty Feet Apart. 



5. Points. — At intervals along the cable on the ridge there should be placed 

 uprights with points that will not corrode. These uprights should be firmly fas- 

 tened to the cable. There is no absolute law as to the distance apart at wliich these 

 points should be placed, l)ut a rule frequently used as an approximate guide is that 

 the distance between them shall not be greater than twice the combined height of 

 the two uprights. By this rule if the points were five feet in height they would be 

 placed about twenty feet apart. There is, however, a tendency among practical 

 lightning-rod men to use shorter and shorter uprights, some as short as 26 inches, 

 but with these short uprights the points are still placed twenty to thirty feet apart. 

 Copper tubes of suitable size and weighing the same per foot as the rods make the 

 best uprights. They are supported by standards in the form of tripods, thus being 

 strongly braced. 



The experiments with the little electrical machine have shown us that the flash 

 selects angles and prominences, and we know that lightning shows the same pref- 

 erence ill this respect. Consequently points should be placed near each end of the 

 ridge, on or heside chimneys, and on cupolas and dormers. Those on or beside 

 chimneys or cupolas should project above them at least eighteen inches. 



On the uprights ornaments of one kind or another, such as bright balls and 

 weather vanes are frequently placed. Scientifically and according to at least three 

 manufacturers of rods in Ontario, the former are of no use in telling whether the 

 building has been struck by lightning, as is sometimes stated by agents. The vanes 



