226 



SCIENTIFIC RECREATIONS. 



The decomposition of water can also be effected by means of the 

 electric current If two tubes or vessels be placed in a vase of water, and 

 the wires from the battery be inserted in them respectively, the oxygen will 

 go to the platinum or positive pole wire, and the hydrogen to the zinc or 

 negative pole. This decomposition or " splitting up " of components was 

 termed ELECTROLYSIS by Faraday, who gave a series of names to the action 

 and the actors in these phenomena (fig. 230). 



Any liquid body, such as the water we have just decomposed for 

 instance, Faraday termed an electrolyte ; the surfaces where the current 

 enters or leaves the body were called electrodes the " ways," from odos, a 

 "way"; the entry is the anode ; the leaving point the katode, from ana, "up," 

 and kata, " down." The electrolyte is divided into two portions, " ions " 

 (" movers "), which move towards the electrodes, which are positive and 

 negative. In the case of the decomposition of water the hydrogen goes to 

 the negative electrode, the oxygen to the positive. 



Fig. 250. Decomposition of water. 



There are a few observations to be made respecting electrolysis. One 

 rule is, that it " never takes place unless the electrolyte is in a liquid state." 

 The liquid state is essential. It is also observed that the components go to 

 the different electrodes ; such elements as go to the negative electrode are 

 termed electro-positive, the others electro-negative; or, as Faraday termed 

 them, " anions " or " kations." The chemical power or electrolytic action of 

 the current is the same at all parts of the circuit ; the quantity of the sub- 

 stance decomposed is in exact proportion to the strength of the current. 

 Faraday measured the strength of the electric current, and invented for 

 the purpose an instrument called the Voltameter. We have mentioned 

 the Galvanometer more than once, and will proceed to describe it. There 

 are several forms of this instrument : the Tangent, the Marine, and the 

 Reflecting Galvanometers, and the Astatic, or " Multiplier." In the first- 

 named the direction of the current is determined by Ampere's rule, which is 

 as follows : 



" Imagine an observer placed in the wire so that the current shall pass 



