Supposed Polarity of Diamagnetic Bodies. 191 
imental helix and the magnet. Such a shake may easily take 
place, and yet (without much experience) not be* perceived. It 
is important to have the cores of such bodies as bismuth, phos- 
phorus, copper, &c., as large as may be, but I have not found it 
o have less than one-eighth of an inch of space between 
b them and the interior of the experimental helix. In order to 
| float, as it were, the core in the air, it is convenient to suspend it 
in the bight or turn of a fine copper wire passing once round it, 
the ends of which rise up, and are made fast to two fixed points 
at equal heights but wide apart, so that the wire hasa V form. — 
This a A gy keeps the core parallel to itself in every part ~ 
| +4 
| of its motio ty 
4 
650. The magnet, when excited, is urgéd by an electric curs - 
rent from five pairs of Grove’s plates, and is then very powerful.’ 
When the battery is not connected with it, it still remains a mag- 
net of feeble power, and when thus employed may be referred to 
as in the residual state. If employed in the residual state,’ its 
3 ometer without any current appearing there. But if theypnaa agnet © 
be employed in the excited state, certain important preeautions + ‘ 
2 are necessary ; for upon connecting. the magnet with the battery - 
and then connecting the experimental helix with the galyanome-" 
"-ter, a current will appear at the latter, which will, in certain cases, 
continue for a minute or more, and which has s tt e appearance of: 
being derived at once from that of bape: At is not.so pro- : 
duced, however, but is due to the. time ocou the irén cor 
ot ninety seconds, or more. On si an " 
sly renewing it, the effect will be repeated, 
oat socobdayy pone third intermission < Sig 
eat fi copa a petiod; | 
op ploy a was made he 2a : 
e ‘eels hp es aes in their 
le vibration to the 
