MAGNECRYSTALLIC CONDITION OF SULPHATE OF IRON. 
39 
an aggregate in a position of unstable equilibrium, and will immediately, as a whole, 
turn and point with the length axially ; whereas the bismuth cubes by such approxi- 
mation will suffer no sensible change. 
2626. The extreme (and the other) associated cubes of the elongated iron arrange- 
ment now have a polar force above that which they had before ; and the whole group 
serves, as it were, as a conductor for the lines of magnetic power ; for many of them 
concentrate upon the iron, and the intensity of power is much stronger between the 
ends of the iron arrangement and the magnetic poles, than it is in other parts of the 
magnetic field. k!iuch is not the case with the bismuth cubes; for however they be 
arranged, the intensity of force in the magnetic field is, as far as experiments have 
yet gone, unaffected by them ; and the intensity of the molecules of the crystals ap- 
pears to remain the same. Hence the iron stands lengthways between the poles ; the 
bismuth crystals, on the contrary, whether arranged side by side, as respects the mag- 
necrystallic axis, so as to stand as to length equatorially ; or end to end, so as to 
stand axially, are perfectly indifferent in that respect, vibrating and setting equally 
both w^ays. 
2627. A given piece of iron when introduced into a field of equal magnetic force, 
and brought towards the pole, adheres to it and disturbs the intensity of the field, 
producing a pointed form of pole in one part with diverging lines of force : a crystal 
of bismuth vibrates with sensibly equal force in every part of the field (2467.), and 
does not disturb the distribution of the power. 
2628. Considering all these actions and conditions, it appears to me that the occur- 
rence of the n distance with a body which is at the same time magnetic and magne- 
crystallic, may be traced to that which causes them and their differences, namely, the 
polarity belonging to the magnetic condition, and the axiality belonging to the mag- 
necrystallic condition. Thus, suppose an uniform magnetic field three inches from 
pole to pole, and a bar of magnetic matter an inch long, suspended in the middle of 
it ; by virtue of the polarity it acquires, it will point axially, and carry on, or con- 
duct, with its mass, the magnetic force, so much better than it was conducted in the 
same space before, that the lines of force between the ends of this bar and the mag- 
netic poles, will be concentrated and made more intense than anywhere else in the 
magnetic field. If the poles be made to approach towards the bar, this effect will 
increase, and the bar will conduct more and more of the magnetic force, and point 
with proportionate intensity. It is not merely that the magnetic field becomes more 
intense by the approximation of the poles, but the proporfion of force carried on by 
the bar becomes greater as compared to that conveyed onwards by an equal space 
in the magnetic field at its side. 
2629. But if a similar bar of magnecrystallic substance be placed in the magnetic 
field, its power does not rise in the same manner, or in the same great proportion, 
by approximation of the poles. There can be no doubt that such approximation 
increases the intensity of the lines of force, and therefore increases the intensity of 
