The American journal of science and arts . nerated within the limits of a few square inches of metal. A few years since, having seen what an intense degree of mag-netic force could be generated in a bar of soft iron, by passinggalvanic currents around it; the idea (very natural to most personswitnessing the same experiment) occurred to me, whether thismagnetism could not in some manner be retained ; I was awarethat so long as soft iron was made the agent it could not; and iftempered steel was used a difficulty would also present itself,and it was not until about eight or ten months since that
The American journal of science and arts . nerated within the limits of a few square inches of metal. A few years since, having seen what an intense degree of mag-netic force could be generated in a bar of soft iron, by passinggalvanic currents around it; the idea (very natural to most personswitnessing the same experiment) occurred to me, whether thismagnetism could not in some manner be retained ; I was awarethat so long as soft iron was made the agent it could not; and iftempered steel was used a difficulty would also present itself,and it was not until about eight or ten months since that thefollowing experiments were put into operation. The object that1 had in view, was to substitute for the iron used in the electro-magnet, red hot steel and cool it suddenly. A few feet of copper wire were coiled as shown in the figure,the arrangement being such, that the galvanism in its circuitwould generate north and south polarities, at the end of the re- 336 Method of Making Permanent Artificial Magnets. Positive Pole. Negative spective coils. The coils were varnished in order that they mightbe immersed in water, without any interruption taking place inthe current of the galvanic fluid. The two extremities of thewire were attached to a battery, consisting of a single pair ofplates, each plate of about twelve square inches. A horse-shoe ofsoft iron was then introduced into the coils to test their magneticpower ; the iron was found capable of sustaining about one anda half pounds. After withdrawing the iron, a piece of steel, ofthe same shape, made red hot, was introduced and both steel andwire were plunged into cold water, and contrary to my expecta-tion the steel was found to be but feebly magnetic. I then re-peated the experiment, with this difference, that before coolingthe steel, I united its two extremities (projecting below the endsof the coils) by a piece of soft iron, which by keeping up thecirculation of the magnetic fluid, enabled me to procure a magnetof s
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