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

  • Ferguson, James, 1710-1776.
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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    foil; the outer coatings of the jars are therefore kept in conducting communication with each other. If there are twelve jars,, they may be placed in three rows of four each : every jar having its charging wire termina- ted by a brass ring instead of a ball, as in a jar intended to be used separately. A brass rod, with balls at its extremities, is to be passed through the rings in each row, in order to connect the inner coatings together : two shorter rods being laid across these, the whole in- ner coating will be connected : as the short rods are moveable, either four jars, eight jars, or the whole bat- tery may be employed, according to the nature of the experiment. A battery is charged and discharged in the same manner as a single jar: it is charged by bringing the wire of its internal coating in contact with the positive conductor of the electrical machine, whilst the outer coating is connected with the earth : it is discharged by connecting the outer and inner coatings with the dis- charging rod, or any other conductor. The height of the uncoated rim of the jar should be proportionate to its size : with a small jar two, or two and a half inches are sufficient, the coated surfaces being then separated by an interval of five inches : with larger jars a rim of about three and a half inches is usually adequate. After having described the modes of obtaining accu- mulations of the electric fluid, it is necessary to obtain some mode of measuring the intensity thus produced. The quadrant electrometer is frequently applied with ad- vantage to this purpose : it consists of a brass stem, which can be fixed into small holes made in the conduc- tor of the electrical machine, and in various parts of electrical apparatus ; this stem carries a graduated qua- drant of ivory ; at the centre of the quadrant is fixed a pivot upon which revolves a thin slip of cane, serving as