GALVANIC INSTRUMENTS 



Fig. 380. 



Simple Galvanic Series. This series, sometimes called 

 Couronne De Tasse, is a simple galvanic battery, and con- 

 sists of a number of glasses, jelly pots, or similar vessels, in 

 each of which are placed two pieces of metals, of dissimilar 

 electric properties ; for example, zinc and copper ; the zinc 

 of one vessel being connected with the copper of the other. 

 The outer cups, or vessels, having a wire only to its extreme 

 plate of metal ; the wire, therefore, of one extremity being 

 joined to the wire of the other extremity, completes the elec- 

 tric circuit, and causes the fluid to circulate around the whole 

 series. Price, in porcelain jars, 25 cts. each series. 



Fig. 331. Faraday s Apparatus for showing the Phenomena 



^ of an Electric Current independent of the Contact of 



\ dissimilar Metals. (Fig. 381.) It consists of a 

 P3-N glass or porcelain trough for the dilute acid, a bent 

 clean zinc plate, and a platinum plate furnished with 

 a curved wire. If a small piece of filtering paper, 

 moistened with iodide of potassium, be placed on 

 the zinc, and the end of the wire be pressed against 

 it when the plates are immersed in the trough, the 

 iodine is thrown down on the filtering paper by 

 voltaic action. Price, $2. 



