Magnetized Nofi-crj/stallitie Substances. 253 



stances. An evpervnentum cruris might be made by means of 

 an electro-magnet without a soft iron core. 



23. In one respect M. Pliicker's views receive a remark- 

 able confirmation by Joule and by Gartenhauser and Miiller's 

 experiments, if it be true that a homogeneous diamagnetic 

 substance is inductively magnetizable to an extent precisely 

 proportional to the magnetizing force, or deviating less from 

 this proportionality than the magnetization of soft iron. For 

 if a complex body were made up consisting of a diamag- 

 netic substance (either solid or in powder) and an extremely 

 small quantity of soft iron in very fine powder or filings, 

 spread uniformly through it ; a small ball of this body would, 

 when acted upon by a feeble magnetizing force, become on the 

 whole magnetized like a ferromagnetic, and would be urged 

 from places of weaker towards places of stronger force. If now 

 the magnetizing force were gradually increased, the "resultant 

 magnetic moment" of the complex body would at first in- 

 crease, then, after attaining a maximum value, decrease to 

 zero, after which it would become " negative," or the ball 

 would be on the whole magnetized like a diamagnetic, and 

 would be urged from places of stronger towards places of 

 weaker force. Such, if I mistake not, is the bearing which 

 M. Pliicker expects of any complex solid consisting of a 

 suitable mixture of ferromagnetic and diamagnetic substances; 

 but mere experiments on soft iron, such as those of Joule and 

 of Gartenhauser and Muller, do not render it probable that a 

 homogeneous feebly ferromagnetic substance, containing no 

 iron, or only a very small quantity and that chemically com- 

 bined, should have its capacity for fresh magnetization dimi- 

 nished by the slight magnetization which the strongest magnet- 

 izing force that could be applied would produce. If however 

 M. Pliicker's experiments be ultimately admitted as conclusive 

 (which I think they certainly must be if those in which the 

 position of the substance is unaltered be found to succeed 

 with a pure electro-magnet), it would be established that the 

 capacity for magnetic induction of a solution of sulphate of 

 iron* (ferromagnetic), in water (diamagnetic), would diminish 

 as the magnetizing force is increased, becoming zero with a 

 certain force ; and negative, so that the liquid would be on the 

 whole diamagnetic, with any greater force. 

 Row, Gare Loch, Aug. 21, 1850, 



* I assume that the sulphate of iron is in a state of complete solution, 

 as it would be with a slight excess of acid. If the liquid be at all turbid, 

 on account of a precipitate of oxide of iron, the phaenomena observed by 

 M. Pliicker might be explained as in the case of the complex solid con- 

 taining soft iron in powder spread through the mass. 



