On the use of the Dynamic Multiplier. 357 



Fig. 2, is an oscillating interrupter differing from the last only in 

 the mode of suspension. 



There are two ways of arranging the wires, so as to produce mo- 

 tion by changing the direction of the current. A single wire may 

 be used having two extra ends, which are to be carried to the other 

 extremity of the bar and crossed before reaching the cups. In the 

 oscillating interrupter the extra ends are soldered to the ends of the 

 wire, at the same extremity of the bar, viz. the top. The other meth- 

 od is to cover the bar with two wires running in different directions. 



Fig. 3, is a side view of a revolving interrupter, which is to be 

 preferred to all other forms. 



The bar may be of larger size and have a brass rim attached to it, 

 to make its motions more regular ; two bars at right angles may be 

 used to increase its speed, but one will be found sufficient. The ex- 

 tremities of the wires are brought down upon the axis, and soldered 

 to upper and lower pieces of copper, which are segments of circles, 

 for dipping into the glass cells for mercury. Single wires will an- 

 swer. There are three methods of changing the direction of the cur- 

 rent. First, by using two coils of wire running in different direc- 

 tions ; 2d, by using a single coil and having four mercury cells, two 

 positive and two negative, and lastly, by having a single coil and 

 two cells ; the extra ends are attached, and crossed on the axis. I 

 have tried all these methods, and prefer the last. A single horse 

 shoe magnet held any where near the extremity of the bar, will keep 

 it in rapid revolution. The most proper disposition of the magnets 

 would be in a circle, having all the poles of one kind in the upper, 

 and all of the opposite kind in the lower half. The revolution is 

 so rapid as to scatter the mercury, if the cells are not sufficiently 

 deep : they are made each of four strips of window glass, having 

 sufficient space between them at the center to allow the axis to pass. 

 The tops of the cells are then covered, and the spaces between the 

 glass strips closed, except where the axis passes^ (The mercury is 

 rapidly oxidized, but the oxide may be saved (as it should be in all 

 cases) and dissolved in nitric acid, for use in small batteries. The 

 nitrate of mercury is far superior, as a motor of electricity, to acids 

 or the cupreous salts. A single pair of plates, the size of a cent, 

 each separated by a strip of gold beater's skin, immersed in the ni- 

 trate of mercury, give results by the dynamic multiplier, equivalent 

 to a battery of four square feet of common construction. If the zinc 

 plate be entirely protected by gold beater's skin, the whole of the 

 mercury may be recovered by precipitation on the copper plate in 



