On the use of the Dynamic Multiplier. 357 
_ Fig. 2, is an oscillating interruptor 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 interruptor 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 interruptor, 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 
