Lesson VII. 







. 23. 



because it produces a long-continued and 

 uniform current. The outside vessel (A), 

 ;nade of copper, and is 

 filled with a strong solution < ; 



vitriol" (B). \ 



that th re is another cylinder placed with- 

 in this, hut separated from tin- eopp r \es- 

 f (D), which is full of holes. 

 Upon the shelf are some blue lumps ; these 

 are crystals of sulphate of copper, placed 

 there to maintain the strength of the solu- 

 tion. Within this second cylinder, 

 is a porous earthen tube, is "a rod of zinc 

 i-ported by a cross piece (i). and 

 surm<> 1 screw (E), which 



s a wire (o); a similar cap and 

 screw 0) is affixed to the outside vessel, 

 a wire (in. Both these 

 1C electric current from 



an we determine the 

 of voltaic eKctii- 



ring that the polarity 

 or disturbance commences at tin- 



tracked, and starts fn 

 i then passes through the I 



tal <>r conducting body, and 

 retur ;rr. 



/'.You Mid 



you would descrih >s of obtain* 



ing oxygen : 

 citj ; please to do so now.' 



P. [Experi iient la I < ere is a shal- 

 low cxlindrieal ;'; 

 sel (Fiy. 24), furnished 

 with two g'ass tuWs (A. 

 and B), which are filled 

 with water acidulated 

 ilphuric acid, and 

 plac d over two small 

 plates of platinum con- 

 uecti-d with two platinum 

 wires pa-sing through 

 the bottom of the vessel 

 (n and p) We will now 

 count ct these wire- with 

 th- t \\ o poles of a Smee's 

 battery. [Doesso.] You 

 se<- tliat bubbles of gas 

 are rising in each tube 

 frni the platinum plates. 

 Y-u see that the gas in 

 the tube over the nega- 

 tive pole or zinc end, occupies twice the 

 space of the gas in the other tube ; the 

 former is hydrogen, and the latter oxygen. 



[See Lessons ix. an<1 x., Catechiim iv., for th 

 characteristic properties of each.] 



QUESTIONS ON LKS< >N VI 

 1. How may the electric equilibrium 

 of two solid bodies be disturbed ? 



->. What do >ou mean by an electro- mo- 

 tor power? and give the scale of tension ? 

 l-lai'i wh.it is meant by a voltaic 

 pile, and how it is constructed. 



\jilain the theory of the action of 

 taie pile. 



by i he I'oles of a 

 voltaic 



G. Explain the difference between a 

 and a Da- 



1 lattery. 



7. How is water decomposed 1>\ 

 electri 



II. 



WE have sen that the galvanic current will produce heat and light, and that it will 

 decompose water. If space 



: poses 



s*lu. ami that we arv 



' n t'*P y be the pictures del.vervU by t ,011 of 



>n, or the service of rlectm-plat* that are ranged upon our tables, 



