331 ELECTRICITY. 



stuck upright in the prime conductor B of the 

 electrical machine ; the earth and moon hanging 

 upon the sharp point of the wire c, a', e, in which 

 wire is a pointed short pin, sticking out horizon- 

 tally at e ; and there is just such another pin at d, 

 sticking out in the same manner, in the wire that 

 connects the earth and the moon. 



When the globe of the electrical machine is 

 turned, the above-mentioned balls and wires are 

 electrified ; and the electricity, flying off horizon- 

 tally from the points c and d, causes 8 and E to 

 move round their common centre of gravity a; and 

 A and M to move round their common centre of 

 gravity b. And as E and M are light when com- 

 pared with S and E, there is much less friction on 

 the point b, than upon the point a ; so that E and 

 M will make many more revolutions about the 

 point b, than S and E make about the point a. 

 The weights of the balls may be adjusted so that E 

 and M may go twelve times round Z>, in the time 

 that S and E go once round a. 



Fig. %. represents a model of a water-mill for 

 grinding corn. A is the water-wheel, B the cog- 

 wheel on its axis, C the trundle turned by that 

 wheel, and D the running mill-stone on the top 

 of the axis of the trundle. It may easily be con- 

 trived and turned also by electricity, if, instead of 

 the round plate D for the mill-stone, there be a 

 horizontal wheel on the axis of the trundle C, with 

 spur-cogs, which will turn two trundles placed on 

 its opposite sides ; and on the top of the axis of 

 each of these trundles, may be a round plate re- 

 presenting a mill-stone ; so that this model has all 

 the working parts of a double water-mill, turning 

 two mill-stones. 



