Prof. F. Horton on High Potential 



connected in series when the battery is not in use, and the 

 box therefore contains 3 sets of 10 small batteries (each set 

 wiving about 40 volts), and 5 sets of 5 small batteries (each set 

 oiving about 20 volts). The sets are insulated by micanite, 

 and they can all be connected in series by means of the 

 plug-keys. The required potential is tapped off by inserting 

 special plugs into holes in the insulated brass pieces con- 

 nected to the cells. In these special plugs the insulated 

 wire leading to the apparatus goes through a hole along the 

 axis of the plug, and the wire is fixed into the metal part of 

 the plug by means of a small screw, the head of which is 

 sunk in the ebonite so that it is not touched by the fingers 

 when handling the plug. Four of these special plugs are 

 shown in the illustration, two in the extreme left-hand brass 

 piece, one in the front of the fourth brass piece, and one at 

 the extreme right hand. They are of the same size as the 

 other plugs and fit into any of the holes in the brass pieces so 

 that the required potential difference maybe obtained. This 

 battery has the advantage of being compact and portable ; 

 it has been found very convenient both for research work 

 and for lecture purposes. 



35 Volt Battery. 



The other arrangement of dry cells which has been found 

 very useful in practice is illustrated in fig. 2. The box 

 contains 25 separate dry cells and gives a total electromotive 

 force of about 35 volts. The cells are connected: in series 

 inside the box and, by turning the handle in the centre, the 

 difference of potential between the two terminals can be 

 increased by approximately equal steps from to 35 volts. 



