Seo. 21.] LIGHTNING-CONDDCTORS. 343 



"Should the rod be struck by liglitning, its eflicacy in caiTying off the 

 shock 'n-ill depend on whether it presents a cotitinuoiis chain of conducting 

 matter, in the line or direction of the discliarge, which is superior to an^" 

 thing within the building. If it docs not, all the glass in the world will not 

 prevent fluid from leaving the rod and ])assing through the building on such 

 conductors as it may find there. 



"The true theory or purposes of the lightning-rod is to facilitate electric- 

 ity in following out its natural laws and tendencies, and nothing can be 

 more truly unscientific or practically absurd than the idea of presentiu" a 

 barrier or obsti'uction to lightning." 



This theory fully accords with all our information upon this subject. 



The following arc the views of" another practical electrician, y. D. Ciish- 

 num, of South Bend, Ind. He says : 



" A conductor for the protection of life and property from the effects of 

 lightning should be so constructed and applied that it will add to the con- 

 ducting power of the building so as to admit of the most intense discharga 

 being securely transmitted, without explosion or damage to the building or 

 structure. 



"Attuactiox. — The utility of a lightning-rod docs not consist in its 

 attracting power. 



" Insulation. — Tlie conducting power of a lightning-rod is frequently 

 'diminished by insulation, and never is increased ; it should never be insu- 

 lated. It may be fastened to the building with braclfcts of wood or stajiles. 



"Points. — The attaching to the ujjper end of a lightning-rod a coj)pcr, , 

 silver, gold, or any kind of a jioint, does not add to the ntiiit}- of the rod, 

 but when attached always diminishes, more or less, the conducting powei 

 of the rod, by breaking up the perfect continuity that a rod should j)osscss, 

 and interrupting its jiolarity. 



"Size. — An iron lightning-rod siiould never have less than throe inches 

 conducting surface, oossessing solidity sufHcicnt to have strength and dura- 

 bility. 



" Construction. — A lightning-rod should not possess in its construction 

 sharp edges, neither should it be in sections nor pieces (the sections or pieces 

 being hooked or screwed together), but it should be all in one piece, possess- 

 ing an equal, even unljroken surface in its wiiolc length. 



"Application. — In the application of the rod to the building the conduct- 

 ing power of the building should be brought into the general lino of con- 

 duction ; tliat is, the rod shoidil come in good metallic contact with all the 

 important metallic substances upon the outside of the building, such as 

 gutters, spouts, etc. That part of the rod that comes in contact with the 

 earth should be increa.scd in its surface and conducting power, s-o that tlierc 

 will not be less conducting surface in contact with the earth than is cxjioscmI 

 to the building and atmosphere, and care should bo taken that the earth 

 around and in citutact with the rod is always moist. 



" SHADE-l^KEiis. — Shade-trees should not bo relied upon as a protection 



