62 DR. FARADAY'S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXI.) 
very probably true, but that the magnetic metals and all their compounds retain a 
certain degree of power to become magnetic by induction, whatever their tempera- 
ture, has now been proved (2344, &c.). The deep magnetic contents of the earth, 
therefore, though they probably do not constitute of themselves a central magnet, 
are just in the condition to act as a very soft iron core to the currents around them, 
or other inducing actions, and very likely are highly important in this respect. What 
the effect of the diamagnetic part may be under the influence of such inductive 
forces, we are not prepared to state ; but as far as I have been able to observe, such 
bodies have not their power diminished by heat (2397.) • 
2453. If the sun have anything to do with the magnetism of the globe, then it is 
probable that part of its effect is due to the action of the light that comes to us from 
it ; and in that expectation the air seems most strikingly placed round our sphere, 
investing it with a transparent diamagnetic, which therefore is permeable to his 
rays, and at the same time moving with great velocity across them. Such conditions 
seem to suggest the possibility of magnetism being there generated ; but I shall do 
better to refrain from giving expression to these vague thoughts (though they will 
press in upon the mind), and first submitting them to rigid investigation by experi- 
ment, if they prove worthy, then present them hereafter to the Royal Society. 
Royal Institution, 
Dec. 22, 1845. 
Feb. 2, 1846. — I add the following notes and references to these Researches : — 
Bkugmans first observed the repulsion of bismuth by a magnet in 1778. Antonii Brugmuns Magnetismus seu 
de affinitatibus magneticis observations magneticce. Lugd. Batav. 1778, § 41. 
M. Le Baillif on the Repulsion of a Magnet by Bismuth and Antimony, Bulletin Universel, 1827, vol. vii. 
p. 371 ; vol. viii. pp. 87. 91. 94. 
Saigey on the Magnetism of certain natural combinations of Iron, and on the mutual repulsions of Bodies 
in general. Ibid. 1828, vol. ix. pp. 89. 167. 239. 
Seebeck on the Magnetic Polarity of different Metals, Alloys and Oxides. Ibid. 1828, vol. ix. p. 175. 
