164 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXX.) 
able; inasmuch as that bar might take more or less of charge during the course of 
the experiments, and so render the magnetic power of the field in some degree variable. 
When the crystal was placed in succession in different media at the temperature of 
66°FAHfi., the results were as follows; — 
In water 542 of torsion, 
In air 543 of torsion, 
In saturated solution of protosulphate of iron . 542 of torsion, 
results which perfectly accord with those obtained in the former cases. 
3380. The red ferroprussiate of potassa is a prismatic salt, which sets most strongly 
in the magnetic field, when the axis of the prism is horizontal and the plane passing- 
through the obtuse linear angles is vertical. A crystal, reduced in length and width 
until these were nearly alike, and having therefore little or no mere paramagnetic or 
diamagnetic set (for the salt is very slightly paramagnetic in air), was placed in the 
magnetic field, surrounded first by air and then by camphine ; the results were as 
follows: — in air the tension force was 314, and in camphine 316; the accordance 
being most close with the results before obtained. 
3381. Thus the old conclusions (2499-2501.) are confirmed ; there appears to be 
no experimental difference in the proportion of the force developed in different direc- 
tions in a magnecrystal by the action of magnetic induction, whatever the nature of 
the medium surrounding it, and whatever the difference in paramagnetic and 
diamagnetic character of the crystals, or the media employed ; crystals differing as 
much as bismuth and carbonate of iron, and media differing as greatly as phosphorus 
and saturated solution of sulphate of iron, having been employed. 
3382. Theoretically, however, there ought to be small differences produced, and 
according to my view of the lines of force, as true representations of the magnetic 
power, they ought to be of the following nature. If a magnecrystal be subjected to 
the action of a constant magnet, whilst the magnetic field, and the whole space 
around the magnet, are occupied by a common medium, as air, and then a small part 
of the field around the crystal be occupied by another medium as in the experiments 
described, then, if the mediiun be a better conductor of the force, i. e. be more para- 
magnetic than the former medium, it ought to determine more force across that 
place ; and that increase of force would be the same as if a stronger magnet had been 
employed, and so the magnecrystal should show a variation: — acting as if more highly 
affected than before, its differential power in two directions should appear greater. 
Or, if the part of the medium around the crystal were replaced by a medium more 
diamagnetic, /. e. a worse conductor, then less force would pass in that direction and 
the magnecrystal should appear weaker than before, and so point with less force. 
Even the very shape of these partial substitutions should have an influence, according 
as it might extend in the axial or the equatorial direction, 
3383. But if uU the medium reached by the powers of the magnet were changed 
at once, and not that part only about the magnecrystal in the magnetic field, then 
