40 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XX.) 
rent was stopped, it returned towards the pole ; but the return was much more pow- 
erful than that due to gravity alone (as was ascertained by an experiment), the plate 
being at that moment actually attracted , as well as tending by gravitation towards 
the magnet, so that it gave a strong tap against it. 
2339. Such is, I believe, the explanation of the peculiar phenomena presented by 
copper in the magnetic field ; and the reason why they appear with this metal and 
not with bismuth or heavy glass, is almost certainly to be found in its high electro- 
conducting power, which permits the formation of currents in it by inductive forces, 
that cannot produce the same in a corresponding degree in bismuth, and of course 
not at all in heavy glass. 
2340. Any ordinary magnetism due to metals by virtue of their inherent power, or 
the presence of small portions of the magnetic metals in them, must oppose the de- 
velopment of the results I have been describing ; and hence metals not of absolute 
purity cannot be compared with each other in this respect. I have, nevertheless, 
observed the same phenomena in other metals ; and as far as regards the sluggishness 
of rotatory motion, traced it even into bismuth. The following are the metals which 
have presented the phenomena in a greater or smaller degree : — 
Copper. 
Silver. 
Gold. 
Zinc. 
Cadmium. 
Tin. 
Mercury. 
Platinum. 
Palladium. 
Lead. 
Antimony. 
Bismuth. 
2341. The accordance of these phenomena with the beautiful discovery of Arago*, 
with the results of the experiments of Herschel and Babbage-}-, and with my own 
former inquiries (81.);};, are very evident. Whether the effect obtained by Ampere, 
with his copper cylinder and a helix §, was of this nature, I cannot judge, inasmuch 
as the circumstances of the experiment and the energy of the apparatus are not suffi- 
ciently stated ; but it probably may have been. 
2342. As, because of other duties, three or four weeks may elapse before I shall be 
able to complete the verification of certain experiments and conclusions, I submit at 
once these results to the attention of the Royal Society, and will shortly embody the 
account of the action of magnets on magnetic metals, their action on gases and 
vapours, and the general considerations in another series of these Researches. 
Royal Institution, 
Nov. 27, 1845. 
* Annales de Chimie, xxvii. 363 ; xxviii. 325 ; xxxii. 213. I am very glad to refer here to the Comptes 
Rendus of June 9, 1845, where it appears that it was M. Arago who first obtained his peculiar results by the 
use of electro- as well as common magnets. 
t Philosophical Transactions, 1825, p. 467. \ Ibid. 1832, p. 146. 
§ Bibliotheque Universelle, xxi. p. 48. 
