356 On the use of the Dynamic Multiplier. 
out the magnets, merely by the action of the coil. ‘The pieces of 
wood separating the mercury floods, or poles of the battery, should 
be arranged in the direction of the radius of the coil, as that is the 
position of equilibrium for the magnet. The opposite poles of a 
magnet, conspiring with the action of the coil, make the revolution 
extremely rapid. The interruption occurs twice in each revolution, 
but it may be made more frequent if the number of partitions in the 
cells be increased, and the magnetic poles in like manner. This 
instrument is liable to one objection. The mercury is often dragged 
across the partitions and the revolution ceases. ‘This may in part 
be obviated by pouring a little water upon its surface. 
_ Fig. 1, is a representation of a vibrating interruptor of my own in- 
vention. A piece of soft iron wire one eighth of an inch in diameter, 
and three inches long, is covered with copper wire, and made to vi- 
brate rapidly between the poles of a horse shoe magnet. It should 
be carefully suspended and well balanced. Its motion is increased if 
the poles just touch the wires, to give the bar a spring. ‘The cups 
for mercury (p and n) are sections of glass tubes ; ris a thumb screw 
for regulating the vibrations of the bar. If the four ends of the wires 
be carefully adjusted near the surface of the mercury, by bringing 
down the screw upon the bar, the vibrations may be rendered incon- 
ceivably rapid. 
