Chap. III Of Electrics and Conductors
All bodies in nature are, with reference to this subject, divided into two classes, electrics and conductors.
It has been fully demonstrated by experiment, that no substance which is a conductor can be excited so as to exhibit electrical phenomena: and in the same manner it has been found, that no substance which can be excited, is a conductor. But as we have already hinted, there is, strictly speaking, no substance which is a perfect conductor or non-conductor; because, on the one hand, the electric fluid meets with some resistance in its passage through the best conductors; and on the other, it is in part transmitted through, or passes over the surface of, most if not all electrics.
The two following lists contain as complete an enumeration of electrics and conductors as the present state of knowledge, in regard to electricity, permits us to make.
The substances are disposed in the order of their perfection; that is, the best conductors and the best electrics are placed at the head of their respective lists, and those of an inferior kind follow, somewhat in the manner of a scale graduated downward. Perfect exactness however is not to be here expected, because the subject forbids it, and some of the specified articles are of classes of substances among which there may be a sensible difference.
Conductors or Non-Electrics
Gold,
Silver,
Copper,
Platina,
Brass,
Iron,
Tin,
Mercury,
Lead,
Semi-metals.
Metallic ores.—Of which those are the best which contain the greatest number of metallic parts and are nearest to a reguline state.
Charcoal, either of animal or vegetable substances—
Animal fluids,
Acids,
Saline substances,
Hot water,
Cold water,
Salt water,
All other liquids except oils,
Red hot glass,
Melted rosin,
Flame and the effluvia of flaming bodies,10
Ice and snow—but not below the temperature of 13° Fahrenheit.
Earthy and stony substances, of which the hardest are the worst.
Glass filled with boiling water,
Vapour or steam of boiling water,
Smoke.
All compounds which contain the above substances in different proportions, are conductors in different degrees.
Non-conductors or Electrics
Glass and all vitrifications; even those of metals.
All gems, of which the most transparent are generally the best.
All resinous substances and resinous compounds,
Amber,
Sulphur,
Baked wood—if not suffered to imbibe moisture.
All bituminous substances,
Wax,
Silk,
Cotton.
All dry animal excrescences; as feathers, hair, wool, horn, &c.
Paper,
White sugar and sugar candy,
Atmospheric air and other gasses,
Oils,
Dry and complete metallic oxyds,
The ashes of animal and vegetable substances,
All hard stones; of which the hardest are the best,
Powders not metallic.
Ice at and below the temperature of 13° of Fahrenheit’s thermometer. According to Mr. Walsh’s and Mr. Morgan’s experiments, the Torricellian vacuum ought to be placed at the head of this list; but the singular nature of a vacuum, though a non-conductor, will hardly entitle it to the name of an electric.