320 Dr. de Haldat on the Universalitij of Magnetism. 



themselves to general considerations, being unable alone to 

 solve the objections proposed by the partisans of special mag- 

 netism, the author had recourse to experiments directed ac- 

 cording to the following considerations. If the property of 

 acquiring the magnetic state belongs only to one body, the 

 partisans of this special virtue must prove, — 1st, that this metal 

 exists in all bodies presenting magnetic pheenomena ; 2nd, 

 that all bodies contain it, and in sufficient quantity to satisfy 

 the magnetic phaenomena developed in the ex])eriments of 

 this class; 3rd, that, whatever be the state of the metal, pure 

 or combined with different bodies, it always preserves its cha- 

 racteristic property. The answers to these questions are given 

 in an article speciallydevoted to an investigation of iron, and an 

 explanation of the processes adapted to detect it in the various 

 substances in which it exists, either in a state of simple mix- 

 ture or of combination. And as excessively weak quantities 

 are able to communicate the magnetic power to the bodies 

 which would contain it, it was indispensable to adopt a pro- 

 cess capable of indicating the minutest quantities. The cha- 

 racteristic precipitate of its solutions by the cyanide of potas- 

 sium furnishing a simple and efficacious means of detecting 

 this metal, the author adopted it, after having convinced him- 

 self that in forming, with the precipitate diluted with water, a 

 transparent column two centimetres (nearly 0'8 of an inch) in 

 length, the experimenter can, on receiving a ray of white 

 light, render perceptible at least a five-thousandth of the 

 quantity of iron in the substances subjected to the magnetic 

 experiment. At the same time all the agents adapted to ren- 

 der the test more sensitive were had recourse to, and each 

 analysis checked by means of a test liquor composed of per- 

 sulphate of iron, the amount of which being excessively small, 

 proved that if this metal had existed in the composition sub- 

 mitted to examination, it would necessarily have been de- 

 tected. 



Sixty substances deprived of iron by the usual means, and 

 found to be chemically pure, were thus prepared and sub- 

 jected to magnetic action, after having received the elongated 

 form which ensures the success of these experiments. Among 

 these substances are the following, whose absolute purity 

 must be theoretically admitted, and which has moreover been 

 proved by experiment : distilled water in the state of ice, 

 hyaline quartz of perfect transparency, the carbonate and mu- 

 riate of ammonia obtained by the combination of their compo- 

 nent principles in a state of vapour, the carbon of the smoke 

 of oil-lamps or pure resins, sulphur washed with hydrochloric 

 acid and repeatedly sublimed, camphor several times sublimed, 



