ELECTRO-MAGNETISM. 119 



lations of the burning metal may also be readily pro- 

 duced. By increasing the number of the plates still 

 more striking effects are obtained. With a pile con- 

 sisting of six or eight plates a foot square, platinum 

 wire connecting the electrodes may be readily fused. 

 Such a battery is also more effectual in the electro- 

 magnetic experiments which follow. 



Describe the 284. MAGNETIC PROPERTIES OF THE CUR- 



magnetic pro- RENT> jf t h e w i re connecting the zinc 



perties of the 



galvanic cur- and copper of the galvanic battery be wound 

 in a spiral, as represented in the figure, the 

 coil, or helix, as it is termed, be- 

 comes possessed of magnetic 

 properties. Like a magnet, it attracts iron, and other 

 magnets, and according to the same laws. 

 How may a 285. THE SUSPENDED BAR. A rod of iron 



^ endedln e Drou g nt near one f tne extremities of the 

 the air ? coil, is not only attracted, but actually 



lifted up into the centre of the coil, where it re- 

 mains suspended without contact, or visible sup- 

 port, as long as the battery continues in action. 

 Science has thus realized the fable of Mahomet's 

 coffin, which was said to have been miraculously 

 suspended in the air. The helix, for this and 

 similar experiments, is wound closer than is rep- 

 resented in the figure, and is composed of several 

 layers of wire. A powerful battery is also essential to 

 success in this experiment. 



286. POLARITY OF THE COIL. That 



What is the ', i 



action of a such a coil has polarity, may be proved, 

 precisely as with a magnet. One end of 

 it attracts the north pole of a magnet, and 



