NATURAL PHILOSOPHY-. 107 



while other? are of awful power. No certain calculation can be made as to 

 whether the coming shock Avill be light or heavy; hence it is prudent to 

 guard against the latter, as in doing so we effectually disarm the former. A 

 light shock will be carried off by a single rod without injury; but the dis- 

 charging power of such a rod being uniform with its receiving power, because 

 of its single outlet, an explosion on its point may occur, charged with so pro- 

 digious a volume of electricity that the capacity of the rod is not great enough 

 to carry it off. Herein lies the great danger of an insufficient conductor. 

 The discharging power being fixed and limited, any excess of electricity will 

 leave the conductor, fly off into the house in search of another, whether it 

 be the stove-pipe or the human body, and do its deadly work. Innumerable 

 cases where such results have followed an excessive discharge on a conduc- 

 tor having a single outlet to the earth are on record. Accounts are often 

 published of injury to buildings, though protected by conductors ; but 

 careful examination into the facts of the case has invariably shown that, 

 though the conductor was free from defect, its capacity was too small to 

 break up and carry off a heavy shock. It follows, then, that the discharging 

 power of a conductor must be equal to its receiving power; that a building 

 should be armed with points on all its prominent projections, because no cal- 

 culations can be made on whicrT prominence the shock may fall; that these 

 receiving points should have numerous discharging points descending to 

 moisture in the earth, and that the whole should be connected by wires in 

 several directions across the roof, so that whichever point may happen to 

 receive the shock will be aided by the entire network of metal in instantly 

 mitigating its intensity by distributing it over a large surface, and passing it 

 off by numerous outlets. The fluid concentrated in the shock had been pre- 

 viously distributed over the surface of an immense body of clouds. How 

 unreasonable it is to expect a single discharging point to pass off the volume 

 of electricity accumulated in so great a body of vapor. It is for these reasons 

 that the cheap conductors are found so often mere traps, bringing the dan- 

 gerous element into a building, instead of leading it away. 



It is a mistake, as well as a useless expense, to put up glass insulators to 

 prevent the lightning from leaving the rod and passing into the house. No 

 flash will quit a properly-constructed rod, because lightning never avoids a 

 good conducting medium to follow a bad one. Hence, the rod being con- 

 tinuous and the staple not so, iron staples are entirely safe. An explosion 

 will shatter glass ones into fragments, and the sleet and ice of winter will as 

 certainly destro3 r them. As few thunder-clouds pass over without discharg- 

 ing their watery contents, the glass insulators become wet, and while in that 

 condition are as good conductors as the iron staples. An immense amount 

 of humbug has been propagated among the people by ignorant peddlers, 

 engaged in selling rods, on the necessity of glass Insulators. They have 

 introduced and sold them as indispensable to protection, either through 

 entire ignorance of their worthlessness, or to enhance the profit on their 

 wares. So also, with respect to gold or platinum points, costing several 

 dollars each. These serve no other purpose but to prevent oxidation. But 

 the point of a lightning-rod rarely or never oxidates. Its exposure to the 

 air causes it to dry rapidly. If galvanized iron be used, as recommended for 

 the wire, it will stand for centuries uninjured. The great object is to make 

 every prominent part of the building bristle with points, and to supply them 

 with an abundance of outlets to the earth, giving to the whole rod a dis- 

 charging power proportioned to, or even greater than, its receiving power. 

 New York Tribune. 



