16 Experimental Researches in Electricity. 



into the shape of a rectangle, or rather of a loop, the upper 

 part of which could be carried to and fro over the galvanome- 

 ter, whilst the lower part, and the galvanometer attached to it, 

 remained steady. Upon moving this loop over the galvan- 

 ometer from right to left, the magnetic needle was immedi- 

 ately deflected : upon passing the loop back again, the 

 needle passed in the contrary direction to what it did be- 

 fore ; upon repeating these motions in accordance with the 

 vibrations of the needle, the latter soon swung through 90° 

 or more. The relation of the current of electricity pro- 

 duced in the wire to its motion may be understood by sup- 

 posing the convolutions of the galvanometer away, and the 

 wire arranged as a rectangle with its lower edge horizontal, 

 and in the plane of the magnetic meridian, and a magnetic 

 needle suspended over and above the middle part of 

 this edge, and directed by the earth. On passing the 

 upper part of the rectangle from west to east, the marked 

 (or north) pole of the needle went west ; the electric 

 current was therefore from north to south in the part of the 

 wire passing under the needle, and from south to north in 

 the moving or upper part of the parallelogram. On pass- 

 ing the upper part of the rectangle from east to west, the 

 marked pole of the needle went east, and the current of 

 electricity was therefore the reverse of the former. " This 

 experiment proves with what remarkable facility currents of 

 electricity are produced in metals moving under the influ- 

 ence of magnets ; and when we reflect upon the universal 

 influence of the magnetism of the earth, the startling 

 inference follows, that scarcely a single piece of metal can 

 be without an electric current existing within it. " It 

 is probable," Faraday adds, " that amongst arrangements of 

 steam-engines and metal machinery, some curious accidental 

 magneto-electric combinations may be found, producing ef- 

 fects that have never been observed, or if noticed, have never 

 as yet been understood : what, for instance, may not be the 



