THE ELECTRIC TELEGRAPH. 



diminution of force due to the imperfect conducting power, or the 

 resistance, as it has been called, of the elements of the battery. 



Without going into the reasoning upon which these investiga- 

 tions are founded, it will be sufficient for our present object to 

 state, that in all cases, a current of greater or less force is trans- 

 mitted to the terminal plate of the series from each of the cells, no 

 matter how numerous they may be, and in some cases batteries 

 have been constructed and brought into operation, in scientific 

 researches, which consisted of as many as two thousand pairs of 

 plates. 



39. To simplify the explanation, as well as because the form 

 described is very generally used for telegraphic purposes, we have 

 here selected the plate battery to illustrate the general principle 

 iipon which all voltaic combinations are founded. In fig. 8 is 



represented the dispo- 

 8. sition of the cylinders 



in a battery formed on 

 the principles of Daniel 

 or Grove, where the 

 metallic connection of 

 each copper or charcoal 

 element of one pair, 

 with the zinc element 



of the succeeding pair, is represented by a rectangular metallic bar 



or wire. 



40. Each combination of two metals, or of one metal and char- 

 coal, which enters into the composition of a battery, is usually 

 called a PAIR, and sometimes an ELEMENT. Thus, a battery is 

 said to consist of so many PAIRS, or so many ELEMENTS. 



The end of the battery from which the current issues is called 

 its POSITIVE POLE, and that to which it returns is called its 

 NEGATIVE POLE. Thus, in the batteries explained above, P is the 

 positive, and N the negative pole. 



Since in the most usual elements, zinc and copper, the current 

 issues from the last copper plate, and returns to the first zinc 

 plate, the positive pole is sometimes called the COPPER POLE, and 

 the negative the ZINC POLE. 



41. The voltaic battery is sometimes called the VOLTAIC PILE. 

 This term had its origin from the forms given to the first voltaic 

 combination by its illustrious inventor. 



The first pile constructed by Volta was formed as follows : A disc 

 of zinc was laid upon a plate of glass. Upon it was laid an equal 

 disc of cloth or pasteboard, soaked in acidulated water. Upon this 

 was laid an equal disc of copper. Upon the copper were laid, in 

 the same order, three discs of zinc, wet cloth, and copper, and the 

 132 



