ELECTRICITY AND MAGNETISM 



apparatus of small power, I undertook to repeat and 

 increase them with a large galvanic battery. 



"Let us suppose that the two opposite ends of the 

 galvanic apparatus are joined by a metal wire. This 

 I shall always call the conductor for the sake of brevity. 

 Place a rectilinear piece of this conductor in a horizon- 

 tal position over an ordinary magnetic needle so that 

 it is parallel to it. The magnetic needle will be set in 

 motion and will deviate towards the west under that 

 part of the conductor which comes from the negative 

 pole of the galvanic battery. If the wire is not more 

 than four-fifths of an inch distant from the middle of 

 this needle, this deviation will be about forty-five de- 

 grees. At a greater distance the angle of deviation 

 becomes less. Moreover, the deviation varies accord- 

 ing to the strength of the battery. The conductor can 

 be moved towards the east or west, so long as it re- 

 mains parallel to the needle, without producing any 

 other result than to make the deviation smaller. 



"The conductor can consist of several combined 

 wires or metal coils. The nature of the metal does not 

 alter the result except, perhaps, to make it greater or 

 less. We have used wires of platinum, gold, silver, 

 brass, and iron, and coils of lead, tin, and quicksilver 

 with the same result. If the conductor is interrupted 

 by water, all effect is not cut off, unless the stretch 

 of water is several inches long. 



"The conductor works on the magnetic needle 

 through glass, metals, wood, water, and resin, through 

 clay vessels and through stone, for when we placed a 

 glass plate, a metal plate, or a board between the con- 

 ductor and the needle the effect was not cut off; even 



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