362 Miscellanies. 



tances, let the rod run through small pieces of iron, one end of which 

 is driven into the house, the other end having an eye sufficiently large 

 to admit the rod. Through this eye, and before the rod is inserted, 

 the neck of a glass bottle, the end of a horn or some other non-con- 

 ductor is placed, so that the building stands isolated. Serious doubts 

 are entertained whether the practice is correct or not. Indeed, there 

 is nobody here who knows how to put up a lightning rod and rest 

 satisfied that he is correct. Will you be good enough to give us the 

 necessary information. With your permission I would make public 

 your views upon the subject, as I have no doubt it may save many 

 lives and much property. 



Answers given by Prof. Olmsted of Y. College, at the Editor'' s request. 



1. The rod should be closely joined together throughout, eitlier 

 by securing one part within another, or by welding the several parts 

 together ; this will prevent the interruption occasioned to the pas- 

 sage of electricity through links or loose joints. 



2. The points of the rod above should be gilt, since the conduct- 

 ing power of iron is impaired by oxidation. 



3. The rod should descend into the ground far enough to be al- 

 ways in contact with moist earth. This depth will vary in different 

 places. In some places five feet will be sufficient ; in others, six or 

 seven will be required ; and in soils peculiarly dry it may be pru- 

 dent in the season of thunder storms, to connect the bottom of the rod 

 (by means of a chain or the rod continued,) with a well or vein of wa- 

 ter. The chain or rod may be enclosed in some substance, or be 

 painted with a thick coat of lampblack, to keep it from rusting. 

 When the bottom of the rod terminates in the ground, it may branch 

 off in several directions. 



4. The height of the rod above the building should be regulated 

 on this principle : that a lightning rod ivill protect a space in every 

 direction from it, of twice its length above the building. Thus, if 

 it rises fifteen feet above the roof, it vi^ill protect a space of thii'ty 

 feet every way, 



5. The rod should be fastened to the house by wooden, in prefer- 

 ence to iron stays. For, although electricity takes the shortest route, 

 yet in case the rod were imperfect, the passage of the fluid into the 

 building would be favored by iron bolts. 



6. The kitchen chimney, being that alone in which a fire is usually 

 kept during the summer, requires to be especially protected. 



