62 
MESSRS. W. DE LA RUE AND H. W. MULLER ON THE 
of contact plugs (h and Ii, fig. 7). Fig. 6 shows that face of the switch which is 
screwed against the inside of the case. 
Fig. 7 shows the means of connecting up the several batteries. The battery on the 
left being represented in circuit by the insertion of brass plugs with ebonite handles 
h, li, into the cylindrical hollow ends of the switch rods ; when this battery is not 
in use the plugs are withdrawn and inserted into the supports shown in the figure 
attached to the end of the case, it being understood that the handle of the switch 
Fig. 7. 
has been depressed to throw the contact springs out of gear. The conducting wire 
has moreover to be rendered continuous by inserting the plug C between the jaws 
Z and A of the insulated plug-connector, which has a space of ‘625 (fth) inch 
between the nearest points of the jaws, a distance absolutely necessary with batteries 
of such high tension as those we have in action. 
For special experiments we have found it necessary to design and have constructed 
a commutator capable of reversing the current many times in a second, that shown 
in fig. 8 represents the form we have found most convenient to employ ; it is 
capable of reversing the current 352 times in a second when the handle is turned 
240 times in a minute, which it is not difficult to do. It will be seen that each 
