TRANSACTIONS OF THE SECTIONS. 
17 
§ubitances possessing a directive tendency, and it was so arranged that the directive 
tradcncv due to structure was always opposed to the influence of length; between 
the points the former tendency succumbed to the latter, while between the flat poles, 
r.r above and below the points, the former was triumphant. It is amusing to observe 
tie strife of these two tendencies in substances possessing a strong directive action. 
A |>l*t* of crystallized carbonate of iron, when properly suspended, will wrench itself 
•ptMBiiiicalljr from one position into the other, nnd find rest nowhere. The simple 
L * winch governs all these actions is, that if the body, cut as above, be diatnag- 
r -' T , its length sets equatorial between the points, but above and below them axial. 
1 " l ‘ l - b 'dv be magnetic, it sets axial between the points, above and below equatorial. 
'I' ihe rotation of a magnetic body, on being removed from between the points, 
» tl*4rs ftom axial to equatorial; while the corresponding rotation of a diamagnetic 
'• -i » always from equatorial to axial. The deportment of wood in the magnetic 
next described. Nearly sixty specimens examined by Prof. Tyndall were all 
; all of them were repelled by the poles of the magnet; cubes of each, 
suspended with the woody fibre horizontal, set, between the excited poles, with 
'.b; t [nrpendicular to the line which unites the poles. Thinking that wood, on 
- 'imtof ns structure, would exhibit those directive phenomena which had beende- 
ii nteu in the case of the bodies mentioned at the commencement, bars were 
1 I. mm nearly forty kinds of wood, the fibre being at right angles to the length 
i . ar ’ 10 the centre of the space, between two flat poles, all those bars set their 
f* r i\ » v' n *° P°* e .‘ Prof. Tyndall afterwards observed the remarkable 
' hirtih h ° m r e0U3 ^magnetic bodies did the same. Bars of sulphur, of 6alt 
-f t'l ° rn ’ 0 ^ x * other diamagnetic substances, when suspended in the cen¬ 
ts ^i a _ H _ n a P ace 1 between two flat poles, set their lengths from pole to pole. Now, 
k'vexMt* ~°“ lea always take up the position of weakest force, it was proved by 
iw.-.L ira . ents > “nd corroborated bv others not cited here, that the line mining 
filial of which ° lo , 00 m '* e9 * n length, and showed an enlarged diagram, the 
f ‘ t “of ferroevan^ 38 f Wtl electric currents themselves decomposing solu- 
w ^satumioH^ >pl 0 P°tassium and nitrate of ammonia, with which the paper 
2 
