FARM BUILDINGS. 319 



into the ground, and away from the premises. The rod 

 may be fastened to the building by glass or well-seasoned 

 wood, boiled in linseed oil, then well baked and covered 

 with several coats of copal varnish. 



The conductors of electricity in the order of their con- 

 ducting power, are copper, silver, gold, iron, tin, lead, zinc, 

 platina, charcoal, black lead (plumbago), strong acids, soot 

 and lampblack, metallic ores, metallic oxides, diluted acids, 

 saline solutions, animal fluids, sea water, fresh water, ice 

 above 0, living vegetables, living animals, flame, smoke, 

 vapor and humid gases, salts, rarified air, dry earth, and 

 massive minerals. The non-conductors in their order, are 

 shellac, amber, resins, sulphur, wax, asphaltum, glass, and 

 all vitrified bodies, including crystalized transparent mine- 

 rals, raw silk, bleached silk, dyed silk, wool, hair and 

 feathers, dry gases, dry paper, parchment and leather, baked 

 wood and dried vegetables. 



Palladium, reckoned among the noble metals, was first 

 discovered by Dr. Wollaston, in 1803. It has been found 

 to possess a conducting power about 50 per cent, greater 

 than copper, and consequently, is the best conductor known. 

 This metal is not liable to oxidation, and is therefore, in every 

 respect the most desirable material for the points or upper 

 extremity of the rods, and for this purpose it has recently 

 been extensively introduced. 



It will be seen above, that water is a tolerable conductor 

 of electricity, and when exposed to rain, all the non-con- 

 ductors are liable to become temporary conductors. To 

 secure them as non-conductors, it is therefore necessary to 

 protect them from contact with rain or moisture. 



Rust or the oxides of metals, destroy their conducting 

 power, and to secure them as conductors, it is essential to 

 keep the rods free from rust, paint, oil or varnish, leaving 

 nothing on the exterior but the pure metal. 



