FAEMEKS' INSTITUTES. 239 



same way, but galvanized. This rod looks like four solid copper wires twisted 

 together, but on cutting into it we find they are iron wires covered with a thin 

 wrapping of sheet copper. This rod looks like a fluted spiral of solid copper, 

 but I have cut the rod with a file, and you see the central core is iron, with only 

 a thin covering of sheet copper. What can we call such rods but humbugs and 

 cheats? 



One common object in the construction of these rods seems to be to give 

 increased extent of surface ; for this purpose we have the tube, bundles of wire, 

 fluted forms, etc. Indeed lightning-rod men claim this increased extent of 

 surface as one of the excellencies of their rods, ''because electricity only exists 

 on the surface of bodies." This is true of static electricity, or electricity 

 standing still, as it is found on the insulated prime conductor of an electrical 

 machine, but it is not true of electricity in motion, as every scientific man 

 knows. There is a vast difference between electricity standing still and elec- 

 tricity in motion by conduction, and in lightning we have to do with electricity 

 in motion, and in most tremendous motion ! Static electricity is confined to the 

 surface of an insulated prime conductor, but electrical conduction takes place 

 through the mass of the conductor. On this point I could quote the highest 

 authorities if it was necessary. 



A rod which is both cheapest and safest is the one I v,"ould show you, and is 

 the one recommended by Prof. Henry of the Smithsonian Institution, viz. : a 

 solid round bar of iron, not less than three-fourths of an inch in diameter. 

 Such a rod can safely conduct any flash of lightning. 



IXSULATIOX. 



Another scientific humbug is the statement of these dealers that a lightning- 

 rod must be insulated from a building ; and for this purpose they place a small 

 glass collar, one-half to three-fourths of an inch thick, in the staples that hold 

 the rod, and want us to believe that the rod is insulated and that thus alone is 

 all danger averted of the lightning leaving the rod and striking the house I A 

 stroke of lightning that can shiver vast oaks, split rocks into fragments, and 

 that can penetrate half a mile to a mile of air (the best of all insulators) before 

 it reaches the rod, will hardly be insulated by a thimble of glass half an inch 

 thick! On this subject Faraday says: "Some persons conceived that it is 

 desirable to insulate the conductor from the wall of a building by glass, but all 

 such contrivances are absurd, since the distance to which the metal could be 

 removed from the wall by the interposed insulation was altogether insignificant 

 compared with the distance through which the lightnnig must pass in a dis- 

 charge from the clouds to the earth.'' — American Journal of Science for 1855, 

 p. 140. 



Indeed a good lightning-rod will afl'ord more protection to a building when it 

 is brought in complete contact with a building than Avhen it is insulated from it. 



LIGIITXIKG-ROD POINT. 



Lightning-rod men make a great point of their lightning-rod point. I exhibit to 

 you a number of these points. They all appear to be tipped with platinum — a 

 matter of great moment in tlie estimation of lightning-rod men because of its 

 infusibility. But when we look carefully into this matter, the excellence of 

 platinum over copper in this respect is not so evident and for two reasons : 1st. 

 Copper has more than seven times the conducting power for electricity that 

 platinum has; 2d. "If equal quantities of electricity, whether obtained from 



