g « ca ¢ « 
Instruments and Dispensed > wr 
+ 
together, does not affect the result. To show this fact, he used. 
| a magnet loaded at its lower extremity with platinum, and =. 
| ing in a vertical position in a vessel full of mercury. The instru- 
* 
| ment represented by figure 3, illus- Fig. 3. s 
| trates the same fact without the in- 
, convenience of using a large quan- 
é tity of mercury, and, in conse- 
quence: of the diminished resist- 
ance to be overcome, exhibits a 
| _ much more’rapid rotation than can 
| be obtained by means of Faraday’s 
' apparatus. A magnet, pointed at 
| both ends, is supported onan agate 
cup A, while its upper end is kept 
in place by slightly entering a small 
cavity in the lower extremity E of 
asmall brass rod passing up through 
the arched top of the sustaining 
_ brass frame-work, and surmounted 
with a cup for making connection 
With a voltaic battery. From one 
side of the same rod, a copper wire 
Passes down into a small cistern 
for containing mercury, resting on 
the shoulder of the magnet near 
its upper end. Two ‘copper wires 
Projecting into this cistern, descend 
into another of ivory, supported on 
4 Stage, and surrounding the mid- 
dle of the magnet, but not touch- 
Ing it. One end of a large bent 
copper wire projects into the inte- 
Mor of the ivory cistern, and the 
other supports a cup for makin 
*? Communication with a battery. On putting a proper quantity 
of mercury into the cistern, and’ transmitting a voltaic current 
through the wires, the whole. movable part of the apparatus will 
Totate with considerable velocity. ; af 
Boston, November 7, 1840. 
