Note 137 — Chapter IX
Reading edition
“A good piece of gutta percha will insulate as well as an equal piece of shell-lac, whether it be in the form of sheet, or rod, or filament; but being tough and flexible when cold, as well as soft when hot, it will serve better than shell-lac in many cases where the brittleness of the latter is an inconvenience. Thus it makes very good handles for carriers of electricity in experiments on induction; not being liable to fracture in the form of thin band or string, it makes an excellent insulating suspender; a piece of it in sheet makes a most convenient insulating basis for anything placed on it. It forms excellent insulating plugs for the stems of gold-leaf electrometers, when they pass through sheltering tubes, and larger plugs form good insulating feet for electrical arrangements; cylinders of it, half an inch or more in diameter, have great stiffness, and form excellent insulating pillars. In these and in other ways its power as an insulator may be useful.”—On the use of Gutta Percha in Electrical Insulation: by Dr. Faraday; Philosoph. Mag., March, 1848.
The following deductions have been given by Faraday, in his Researches in Electricity, a work of most extraordinary merit, being one of the most perfect examples of fine inductive philosophy which we possess in the English language:—
“All bodies conduct electricity in the same manner from metals to lacs and gases, but in very different degrees.
“Conducting power is in some bodies powerfully increased by heat, and in others diminished, yet without one perceiving any accompanying essential electrical difference, either in the bodies, or in the change occasioned by the electricity conducted.
“A numerous class of bodies insulating electricity of low intensity, when solid, conduct it very freely when fluid, and are then decomposed by it.
“But there are many fluid bodies which do not sensibly conduct electricity of this low intensity; there are some which conduct it and are not decomposed; nor is fluidity essential to decomposition.
“There are but two bodies (sulphuret of silver and fluoride of lead) which, insulating a voltaic current when solid, and conducting it when fluid, are not decomposed in the latter case.
“There is no strict electrical distinction of conduction which can as yet be drawn between bodies supposed to be elementary, and those known to be compounds.”