en. xxxvi. FAR AD A Y'S EXPERIMENTS. 375 



electricity and magnetism, and he soon saw that if an electric 

 current going round a wire gave rise to magnetic action at 

 right angles to it, he ought to be able to make an electric 

 wire revolve round a magnet, and a magnet round an elec- 

 tric wire. Accordingly, he took two cups of mercury, A B, 

 Fig. 67, and drilling a hole in the bottom of each, he 

 passed the wires ^, /, of a battery up into them ; then he 

 took two magnets d, d' ; d he fastened by a thin thread to 

 the battery wire in the cup A, so that it floated upright in 



FIG. 67. 

 Faraday's Experiments on the Rotation of a Magnet and of an Electric Wire. 



A B, Section of cups of mercury, c, Copper rod. , The current coming in at e passes 

 up through the mercury in A, and along the rod c down into the mercury in B, 

 and back by c to the battery. On its way it causes the floating magnet, d, to 

 revolve round the rod, f, and the loose wire, /', to revolve round the fixed 

 magnet, a '.' . 



the mercury, and the top of it could move round easily ; the 

 other magnet, d' , he fixed firmly upright in the cup B. He 

 then hung the copper rod c above the cups, so that the end 

 /, which was fixed, dipped into the cup A, and the other 

 end, which was made of a loose movable wire, f', dipped 

 into the cup B. Thus in A the magnet was free to move 



