668 EFFECTS OF THE GALVANIC CURRENT. 



The size of the elements varies considerably. For experiments 

 like ours, which are always on a small scale, Grove's elements of 

 12 cm height, and Bunsen's of 18 cm , are quite sufficient. When the 

 current outside the battery has to traverse long and thin wires, as 

 in experiments on telegraphy, or bad conductors, such as liquids, as 

 when chemical decomposition is to be effected, small elements pro- 

 duce nearly the same effects as large ones ; but if the connection is 

 made by well-conducting, stout, short wires, as in experiments on 

 the heating and magnetic effects of the current, large elements act 

 much more powerfully than small ones. 



For experiments on a large scale no general rules can be pre- 

 scribed. The arrangement which is most suitable and economical 

 for a given purpose may, however, be determined in each case, regard 

 being had to the length, thickness, and conducting power of the 

 connecting wires, and various other circumstances, according to* two 

 laws, respectively called Ohm's and Faraday's law, upon neither of 

 which we can further enter in this work. 



49. Effects of the galvanic current upon conductors. 

 The galvanic current has so little tension that mechan- 

 ical effects like the perforation of substances cannot be 

 produced by it, for bad conductors are not traversed 

 by it. In order to pass the current through the 

 human body, the parts of the skin which are brought 

 into contact with the terminals of the battery must be 

 moistened at least with water, or better with salt water, 

 to increase the conductivity. But even then the 

 sensible effect is very small, and only a strong battery 

 of a great number of elements will produce a shock. 

 A feeble current, however, is sufficient to excite the 

 nerves of taste of the tongue. The two terminals may 

 either be placed side by side, 5 or 10 mm apart, upon the 

 point of the tongue, or one may be placed across the 

 middle of the tongue while the other is made to touch 

 the point of it ; in the latter case the effect upon the 

 taste is particularly distinct at the point of the tongue 

 touched by the wire. Either of the terminals, when 



