Lectures on electricity / by James Ferguson, F.R.S.

  • James Ferguson
Date:
1825
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on electricity / by James Ferguson, F.R.S. Source: Wellcome Collection.

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    former of these are called Non electrics, or Conductors: and of this sort are all kinds of metals, living creatures, water, and moist wood ; but metals are found to be the best of all conductors. The latter, which do not admit the electric fluid to pass through their pores, are called Electrics, or Non-conductors: and of this sort are glass, wax, rosin, dry glue, baked wood, and silk. But if either of these be wetted with water, the water that adheres to it will become a conductor.—Consequently, when any body is to be used as a non-conductor, it should be well wiped with a dry warm cloth, to clear it of damps, which it may have contracted from the humidity of the air, or from people’s breath. 4. The quantity of electric fire which every body has lying dormant in it, is called its natural quantity ; and this would also remain motionless and invisible if nothing disturbed it. But when any more is forced into it, as, suppose at one end, the whole is instantly put into motion thereby, and begins to be driven out at the other, if it can find a passage ;3 as if a long narrow tube, open at both ends, be filled with water, and laid on level ground, the water will remain at rest in the tube ; but, if a syringe be filled with water, and fixed to either end of the tube, and then the piston of the syringe be pushed inward, to force more water into the tube, the whole water in it is thereby instantly put into motion, and it begins to run out at the other end. 5. The earth is the grand source of electric fire, and no additional quantity can be forced into any body but from the earth. If the body be a free conductor, and has a communication with the earth by means of any other conducting substance, as metal, or by a table to, the floor and walls of a room, and from thence to the earth, the electric fire will run as fast from the conduc- Note 3. In conductors of electric fire, sharp points arfe as free passages, as the open ends of tubes are for water.—Author.
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