SCIENCE OF COMMON THINGS. 



291 



Construction of a galvanic battery. 



Origin of the term "galvanism.'' 



Fig. 86. 



contact is made and broken, Here, then, we have distinct evidence of 

 the presence of free electricity, developed apparently by simple contact. 



1891 What is the simplest way of exciting a current of galvanic elec- 

 tricity f 



By arranging a series of metal plates in a 

 pile, placing them in pairs, with a wet cloth 

 Between them, it berng necessary that one 

 of each pair should be more easily oxidized 

 than the other. The simple contact of these 

 plates will produce a feeble and continued 

 galvanic current. 



Fig. 86 represents an arrangement of this character. 



180S What is such an arrangement of plates for pro- 

 ducing electrical currents called f 



A galvanic or voltaic battery. 



1893 Why are the terms "galvanic" and "voltaic" 

 applied ? 



They originated in honor of Galvani and 

 Volta, the Italian philosophers who first de- 

 veloped these phenomena of chemical electricity, and 

 the means of producing them. 



1894 Are there many metals or other substances which, wlien brought 

 together, are capable of producing galvanic action f 



The number is quite large ; among them we may 

 enumerate the following : zinc, lead, tin, antimony, 

 iron, brass, copper, silver, gold, platinum, Hack lead or 

 graphite, and charcoal. 



1895 Witt any two of these brought together produce a galvanic current f 



They will : but they possess the power in different 

 degrees ; and the more remote they stand from each 

 other in the order above given, the more decidedly will 

 the chemical electricity be developed. 



Thus zinc and lead will produce a voltaic battery, but it will be much 

 less active than zinc and iron, or the same metal and copper, and this last 

 less active than zinc and platinum, or zinc and charcoal. 



1896 Does galvanic or voltaic electricity appear to consist of two kinds, 

 positive and negative, as in ordinary electricity ? 



It does ; positive electricity always flows from tlie 

 'metal which is acted upon most powerfully, and nega- 

 tive electricity from the other. 



