204 Common Science 



of electrons; the other part has unusually few. The 

 parts with unusually large numbers of electrons gather 

 around the zinc ; so the zinc is negatively charged, 

 it has more than the ordinary number of electrons. The 

 part of the sal ammoniac with unusually few electrons 

 goes over to the carbon; so the carbon is positively 

 charged, it has fewer than the ordinary number of 

 electrons. 



Making the current flow. Now if we can make some 

 kind of bridge between the carbon and the zinc, the 

 electrons will flow from the place where there are many 

 to the place where there are few. Electrons can flow 

 through copper wire very easily. So if we fasten one 

 end of the copper wire to the carbon and the other end 

 to the zinc, the electrons will flow from the zinc to the 

 carbon as long as there are more electrons on the zinc ; 

 that is, until the battery wears out. Therefore we have 

 a steady flow of electricity through the wire. While 

 the electricity is flowing from one pole to the other, 

 we can make it do work. 



Experiment 64. Set up two or three Samson cells. 

 They consist of a glass jar, an open zinc cylinder, and a 

 smaller carbon cylinder. Dissolve a little over half a cup 

 of sal ammoniac in water and put it into the glass jar ; then 

 fill the jar witli water up to the line that is marked on it. 

 Put the carbon and zinc which are attached to the black jar 

 cover into the jar. Be careful not to let the carbon touch 

 the zinc. One of these cells will probably not be strong 

 enough to ring a doorbell for you; so connect two or three 

 together in series as follows : 



Fasten a piece of copper wire from the carbon of the first 

 cell to the zinc of the second. If you have three cells, 



