16 
REPORT— 1854. 
however, this be true, the bismuth bar, when the current circulates round it, muc 
have its two ends in different states; but if in different states, then if we mak. tl» 
two poles acting upon the ends of the bar alike, we ought to have attraction «t 
end, and repulsion at the other, — the result of their opposing actions being that the 
bar must remain undetected. This experiment has been made, and the rr*«lt .• 
in perfect accordance with the conclusion just expressed; when both msiM ■- 
poles are of the same name they completely neutralize each other. Follow me up u • 
inductive reasoning, it is easy to see thut if what has been stated be correct, win •< 
bring two magnets, with poles of the same name, to bear upon the two end* I * 
bismuth bar, the direction of the force emanating from the two poles bring the «*'. ! 1 
the repulsion of one end and the attraction of the other, instead of. as in tin' mm* 
disposition, neutralizing each other, ought to constitute a mechanical couple in m 
ing to deflect the bar; and if two other like poles, but of opposite name* o a 
former two, he caused to act upon the bar, the force of deflection ougr. - 
increased. In this form the experiment was made before the Section. * 
magnets were made U6e of; the two poles to the left were of the ssnie 
the two to the right were of the opposite quality. The result coincided w ' ^ 
author's anticipations, and the bar was promptly deflected. lhr*e 
without any exception, are all corroborative i.f tiic view, that diamagn' r 
possess a polarity opposed to that of magnetic bodies,—but they d" , 
the physical theory of Weber is correct. Indeed, it**s scarcely possible t m 1 1 
thesis can stand in opposition to the experimental evidence which can 
to bear against, it. One consequence of the truly beautiful tlu-ory referr ^ 
when the particles of a diamagnetic body are caused to approach each " c ■ ( 
of their approximation will be to enfeeble the magnetic action wong 
approach. This view is controverted by experiment, which proves . j, 
mation of diamagnetic particles has un effect precisely opposite to tna 
the theory. 
Professor Tyndall exhibited experiments toshow some Peculiarity , - 
Field. The Professor showed that a piece of soft iron suspended bctvvi_ ^ 
ol an electro-magnet set its longest horizontal dimension from pole# «« , ... 
netism of the cores being sufficient to produce theeffect. This is tlw ^ 
rnent of magnetic bodies, hut. it is by no means universal. By mec 1 j M ,,• ■ 
pressure for example, the structure of a magnetic body can be so action*^ ! 
shortest horizontal dimension sets from |K)le. Prof. Tyndall exlu 1 a bM |, 
kind where the body operated on was compressed magnetic dust- jj ^ ^. , 
opposing tendencies were at work, — the tendency due to length, w , ( j lC |jn« r 
the length axial ; and the tendency due to structure, which snug " . ,v»> I 1 
pendicular to the length axial. Between the flat poles the latter ..-action o< 1 
dominant, but between pointed poles this was not the case; here Hn of ,, ;I 5 • 
ends of the magnetic mass by the points constituted a mechanical ^ j t0 dr*“ ; | 
s rength to overcome the directive tendency which was due to strut. • oU t of ^ 
mass into the axial line. But in raising or lowering the body ,j je djj.trK ’ 
Bphere of this local attraction, by bringing it into a position , 
of the magnetic field resembled that existing between the Hat ’ p |,.vr.^ f 
the axial position and turned into the equatorial- The complwn« , “ it ** 
were exhibited by diamagnetic bodies. A normal bar of bismuths t hi s t ub'' ir . 
angles to the line joining the poles; hut Prof. Tyndall exhibited a oar ^ ^ - 
which set between the flat poles exactly as a magnetic body. r , it f " n , 
between the points set equatorial. On raising it or lowering it. » of t o< 
W„ eqaa !°L nal P°‘ Uion ai »' 1 axial. In this case the local Jg*-* thus 
between the points caused the bar to set equatorial, the influence f o <rf 
,r,' na mg °, ver ,. the influence of structure; but removed fr “® “ ( )Sie b * r '’ 
T t | n, ? e • ir ‘‘f t,ve tende «cy of the mass triumphed, and « _ the pl»* 
Tlie b * r . ,n th '« was cut with its length at right an„Ji lam *. 
most eminent deavage of the b.smuth :-it is a proved fact. thattha*P 
nolJ UC j ,C K ° f ,0r ?‘ is ar,nulk ' d - always set at right angles to J * 
poles, and hence where they are transverse to the length, *»**&<> 
1 hese phenomena were examined in a great number of cases; bars 
