ELECTRICITY. 



powder has often an effect upon their 

 powers of conducting electricity. Snow 

 conducts less readily than ice of the 

 same temperature. The same is the 

 case with powdered charcoal, when 

 compared with the same substance in 

 its entire state. But glass, on the con- 

 trary, acquires some conducting power 

 by being pulverized, as was ascertained 

 by Van Swinden, who extended the same 

 observation to sulphur. 



Many bodies, which, in their usual 

 state, are good conductors of electricity, 

 lose this power when they are made 

 very dry. This is the case with recent 

 vegetable and animal substances, their 

 conducting power appearing to be de- 

 rived solely from the fluids they con- 

 tain. 



(24.) Strictly speaking, there is no 

 substance hitherto known that is per- 

 fectly impervious to electricity ; for the 

 intensity of that agent may be so in- 

 creased as to force it, for a certain small 

 distance, through all bodies : neither is 

 there any body in which the conducting 

 power is infinitely great ; that is, which 

 opposes no resistance to the transmission 

 of electricity. If the degree of conduct- 

 ing power which bodies possess could 

 be ascertained with sufficient precision, 

 they might be arranged in progressive 

 order ; but the present state of our 

 knowledge affords only an approxima- 

 tion to such a series. As a table of 

 this kind, however, with all its imper- 

 fections, may be of great use, we sub- 

 join the following, in which the different 

 bodies are arranged in one series, begin- 

 ning with those which have the greatest 

 conducting power, and terminating with 

 those that have the least. The order in 

 which they possess the power of insu- 

 lating is, of course, the reverse of this. 



Catalogue of Bodies in the Order of their 



conducting Power. 



The perfect, or least oxidable metals. 

 The more oxidable metals. 

 Charcoal prepared from the harder 



woods, and well burned. 

 Plumbago. 



The concentrated mineral acids. 

 Powdered charcoal. 

 Dilute acids. 



Solutions of metallic and neutral salts. 

 Metallic ores. 

 Animal fluids. 

 Pure water. 



Ice above 13 Fahrenheit, 

 Snow. 

 Living vegetables. 



Living animals. 



Flame. 



Smoke. 



Steam. 



Metallic salts. 



Salts with alkaline or earthy bases. 



Rarefied air. 



Vapour of alcohol. 



Vapour of ether. 



Earths and stones in their ordinary 



state. 



Pulverized glass. 

 .Flowers of sulphur. 



Dry metallic oxides. 



Oils. 



Vegetable ashes. 



Animal ashes. 



Diy transparent crystals. 



Ice below 13 Fahrenheit. 



Phosphorus. 



Lime. 



Dry chalk. 



Native carbonate of barytes. 



Lycopodium. 



Caoutchouc, or Indian rubber. 



Camphor. 



Siliceous and argillaceous stones in 

 proportion to their hardness. 



Dry marble. 



Porcelain. 



Baked wood. 



Dry atmospheric air, and other gases. 



White sugar, and sugar crystallized. 



Leather. 



Dry parchment. 



Dry paper. 



Cotton. 



Feathers. 



Hair, especially that of a living cat. 



Wool. " 



Dyed silk. 



Bleached silk. 



Raw silk. 



Transparent gems. 



Diamond. 



Talc. 



Metallic vitrifications. 



Glass, and other vitrifications. 



Fat. 



Wax. 



Sulphur. 



Resins, and bituminous substances. 



Amber. 



Gum-lac. 



Although the precise point in the 

 scale which forms the separation be- 

 tween conducting and insulating bodies 

 must, of course, be somewhat indefinite, 

 we have endeavoured to mark it by the 

 division in the above table. 



(25.) It appears, from the experiments 



