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.

    17/112 (page 13)
    SECTION III. A Description of an Apparatus, belonging to the Machine, for making Electrical Experiments. ' Plate I. Fig. 1. 16. 0 and P are two little balls, made of pith of elder, to which the ends of a fine linen thread (about seven or eight inches long) are fixed. When they are used, they are hung by the middle ot the thread upon a wire N, close by a round ball of metal, which is fixed upon one end of the wire ; and the other end is then stuck into a hole in the end G of the prime conductor G EL 17. c d is a crooked wire (which must not be sharp at the bended parts) to be stuck into a hole in the upper- most side of the prime conductor-ball G. The top ot this wire must be sharp above d; and efg h ik is a fly made of small brass wire ; the ends of each arm next the centre being fixed into a brass cap, which is to be put upon the point of the crooked wire; and the other ends of all the arms are bent one way, in a horizontal direction, and terminate in sharp points. Each bended part e,f,g,h,i,k, must make a sort of aright angle with the rest of the arm between it and the center, and these bendings must be roundish, not sharp corners. When this fly is put upon the top of the crooked wire cd, it hangs like a mariner’s compass upon the pin that supports it. 18. Q is a brass hook fixed to a cross bar of brass, from which hang three bells 11, S, T, with their clappers LJ and V, which are small brass balls.—The bells R and T are hung by metal chains; the middle bell S by a silk ]ine, and the clappers by silk threads.—A metal chain W, hangs from the middle bell, the lower part of this chain lies on the table (to which the electrical machine is fixed) and a piece of silk cord w is tied to the lower end of the chain.