. The London, Edinburgh and Dublin philosophical magazine and journal of science. ing withthe ring-magnet are indicated in fig. 6, which needs littleexplanation, except perhaps with regard to the arrangementfor standardizing the ballistic galvanometer. For this purpose an auxiliary ring-magnet of known dimen-sions and having a non-magnetic core was used. Its secondary,in series with that of the iron ring-magnet, formed, in circuitwTith the galvanometer and a coil of 100 ohms, the secondarycircuit, as it remained throughout the experiments. On re-versing a known current in the primary of the au
. The London, Edinburgh and Dublin philosophical magazine and journal of science. ing withthe ring-magnet are indicated in fig. 6, which needs littleexplanation, except perhaps with regard to the arrangementfor standardizing the ballistic galvanometer. For this purpose an auxiliary ring-magnet of known dimen-sions and having a non-magnetic core was used. Its secondary,in series with that of the iron ring-magnet, formed, in circuitwTith the galvanometer and a coil of 100 ohms, the secondarycircuit, as it remained throughout the experiments. On re-versing a known current in the primary of the auxiliary coil,the resulting throw of the ballistic galvanometer was a measureof its sensitiveness to induction alterations in that particularsecondary circuit, whether taking place in the core of theauxiliary coil, or in that of the iron ring-magnet. Such 224 Dr. D. K. Morris on the Magnetic Properties standardizing throws were observed before the readings ateach temperature, and in this way direct compensation wasmade for alterations in the resistance of the secondary The standardizing throw and the numerical data of theiron ring-magnet being known, it was possible to obtain fromeach ballistic observation the change of magnetic inductionin the iron core to which it was due; correction being ofcourse made for the induction which did not pass through thecore. and Electrical Resistance of Iron. 225 The magnetizing current was measured with a tangentgalvanometer, whose indications were compared with those ofa standard Weston ammeter. The magnetizing force wasassumed to be uniform in intensity throughout that part ofthe section of the ring occupied by the iron; which assump-tion is, in the present case, but approximately true, thoughthe oblong cross-section favours the uniformity. Description of the Experiments. The iron cores in their initial condition may be regardedas unannealed; for the original annealing was destroyedduring their preparation. To study the effects of a
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