chap, xv.] SPAMER'S INDUCTION COIL. 155 



In the left part of the case is the cell, and behind 

 this the bobbins are provided. A is the iron core, 

 shown in the figure partly drawn out, which is kept 

 at any height by a sliding spring and which allows 

 the current to be diminished with ease. The cell 

 consists of an ebonite or glass jar, in the cover of 

 which the carbon is fixed hermetically. To enable 

 the cell to be taken out, the clamp E is unscrewed, 

 and the brass piece forming the connection between 

 the carbon and the apparatus, thus made free, is 

 turned to the front. 



Behind E a zinc rod z rises from the cell. It is 

 fixed bv a screw to a brass fork sc, which can be turned 



v 



to the back. This is done when the apparatus is not 

 in use, and in this case the cell is closed by an india- 

 rubber cork. 



The zinc rod, after having been cleaned from the 

 adhering acid, is put into the black groove provided in 

 the left wall of the case. In order to put the apparatus 

 in action the carbon is fixed to the clamp E and the 

 zinc rod connected with the brass fork is slowly 

 lowered into the cell until it is immersed in the liquid, 

 which usually will be perceived by the hammer being 

 put in vibration. This may be facilitated by touching 

 the hammer with the finger. As a rule the zinc rod 

 ought not to be immersed any deeper than is wanted 

 for making the interrupter act. For the first hours of 

 use 10 to 15 nun. immersion are sufficient. When 

 the current is getting weaker the zinc rod must be 

 lowered, but then a new filling up of the cell will 

 soon be required. The liquid consists of : 



Potas. bichromici .... 8 parts 



Aq. dest. ...... 100 



Acidi sulph. puri .... 15'0 ,, 



Hydrarg. bisulph. . . . . I'O 



This quantity allows the cell to be twice filled up. 

 Before filling again, the cell jar ought to be rinsed 



