1854. ] OF THE ROYAL INSTITUTION. 457 
WEEKLY EVENING MEETING. 
Friday, June 9. 
Str Henry Howuanp, Bart., M.D., F.R.S., Vice-President, . 
in the Chair. 
. Proressor Farapay, D.C.L., F.R.S. 
On Magnetic Hypotheses. 
Tuts discourse, the purpose of which was to direct the attention of 
the audience to the different hypothetical attempts made to account 
physically for the known properties of matter in relation to its 
magneto-electrical phenomena, followed on very naturally to that 
of Dr. Frankland on the 2nd instant, who then gave an account 
of the different views advanced by Davy, Ampere, and Berzelius, 
of the manner in which electricity might be associated with the 
atoms or molecules of matter, so as to account for their electro-che- 
mical actions, and of the logical and experimental objections which 
stood in the way of each. On the present occasion reference was 
first made to Coulomb’s investigations of mutual magnetic actions ; 
to the hypothesis advanced by him, that two magnetic fluids, asso- 
ciated with the matter of magnetic bodies, would account for all 
the phenomena; and to Poisson’s profound mathematical investiga- 
tion of the sufficiency of the hypothesis. Then Oersted’s discovery 
of the relation of common magnetism to currents of electricity was 
recalled to mind: —hence an enormous enlargement of the scope 
of magnetic force and of our knowledge of its actions; and hence 
Ampeére’s beautiful investigations, and his hypothesis (also sustained 
by the highest mathematical investigation) — that all magnetic phe- 
nomena are due to currents of electricity ; andthat in such bodies as 
magnets, iron, nickel, &c. the atoms or particles have naturally 
currents of electricity running round them in one direction, about 
what may be considered as their equatorial parts. After Oersted’s 
time, further experimental discoveries occurred; currents of elec- 
tricity were found competent to induce collateral currents, and 
magnets proved able to produce like currents; thus shewing the 
identity of action of magnets and currents in producing effects of 
a kind different to ordinary magnetic attractions and repulsions. 
Then diamagnetism was discovered, in which actions analogous to 
those of ordinary magnetism occurred, but with the antithesis of 
attraction for repulsion and repulsion for attraction: and these 
wee so extensive, that whatever bodies were not magnetic proved 
tobe diamagnetic; and thus a// matter was brought under the 
dominion of that magnetic force, whose physical mode of action 
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