262 



VOLTAIC ELECTRICITY. 



the + electrode, the bismuth representing the + plate and carrying 

 the electrode, while the solder takes the place of the liquid. 

 Just as a number of Voltaic elements may be connected, so may a 

 number of thermo electric pairs, the arrangement being shown in 

 Fig. 209. 



414. The Thermo-electric Pile. Several 

 thermo-electric pairs, generally five, six, or seven, are 

 arranged in a vertical series, as shown in Fig. 209, the 

 intervening spaces being much reduced, the successive 

 bars separated by strips of varnished paper only, and the 

 wire connection omitted. A similar series may be united 



to this by soldering the free end 

 of the antimony bar of one series 

 to the free end of the bismuth 

 bar of the other, the two series 

 being separated by a strip of 

 varnished paper. Any desirable 

 number of such series may be 

 thus united, compactly insulated, 

 and set in a metal frame so that 

 only the soldered ends are open 

 to view. The free end of the 

 antimony bar, representing the 

 -f electrode, and the free end of 



the bismuth bar, representing the electrode, are con- 

 nected with binding screws, which may be connected with 

 a galvanometer. The complete apparatus, with the addition 

 of conical reflectors, is called a thermo-electric pile or mul- 

 tiplier. It is shown in Fig. 210. 



EXEBCISES. 



FIG. 210. 



1. (a.) Draw a figure of a simple Voltaic element. (&.) State 

 what is meant by the electric current, (e.) Indicate, upon the 



