Force of Magnetization. 



291 



The first form of cell, which we used, consisted of two glass 

 tubes, a and o (figure 1), about l cm in diameter and 10 cm long. 

 These were closed at the lower end and were connected by a 



^■^r^v 



narrower glass tube (c), about 50 cm in length. The electrodes, 

 e x and e„, consisting of soft-ir.on wire, were inserted through 

 the open ends of a and o. They were exposed to the liquid 

 for about l cm at their lower ends. When this apparatus was 

 filled with a liquid capable of dissolving iron, it formed a sin- 

 gle cell, one terminal of which could be placed between the 

 poles of an electro-magnet, while the other was well outside 

 of the field. When the free ends of the wires, e x and e„ were 

 connected through a sensitive galvanometer, it was found that, 

 although the terminals were taken from the same piece of 

 wire, and were immersed in the same liquid, a measurable cur- 

 rent was always flowing in the circuit. The electro-motive 

 force was constant neither in amount nor in direction. In 

 many liquids it changed but slowly, however, and could be bal- 

 anced by means of a variable counter- 

 electro-motive force introduced into 

 the circuit. For this purpose a 

 Daniell's cell was placed in circuit 

 with two variable resistances, R and 

 r (figure 2). The cell with iron 

 electrodes was shunted around r, 

 and the ratio ~R/r was so adjusted 

 that the current in the shunt circuit, 

 due to the Daniell cell, was just 

 sufficient to reduce the galvanometer deflection to zero. The 



