Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . described in <§. 298 isvery convenient both for communicating and re-moving magnetism. On account of its power, barsof considerable size may be fully charged by it. Ifthe steel magnet has not the same, or nearly thesame, width, from pole to pole, as the electro-magnet,it can be charged by drawing each half separately MAGNETOMETER. 191 over the proper pole of the electro-magnet, in themanner described in §251, for bar magnets. 307. Magnetometer. — A
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . described in <§. 298 isvery convenient both for communicating and re-moving magnetism. On account of its power, barsof considerable size may be fully charged by it. Ifthe steel magnet has not the same, or nearly thesame, width, from pole to pole, as the electro-magnet,it can be charged by drawing each half separately MAGNETOMETER. 191 over the proper pole of the electro-magnet, in themanner described in §251, for bar magnets. 307. Magnetometer. — A simple application ofthe electro-magnet brings us at once to a very usefulinstrument, the Magnetometer, represented in Its use is to measure the magnetizing powerof galvanic currents. The form in which it is nowdescribed is new. It consists of a vertical electro-magnet, of the U form, with an armature above it,attached to the short arm of a balanced lever. Thelong arm of the lever is graduated decimally to meas-ure, by means of weights of from 100 grs. to , the force required to detach the armature from Fis;. the electro-magnet when connected with the batterywhose power is to be determined. The lever is sup-ported on an axis with knife-edge bearings. Thearmature may also be suspended on knife edges at-tached to the beam. On the under surface of thearmature is brazed a thin plate of brass, to preventits adhesion to the poles. A difference of magnetiz-ing power of 10 grs. can be estimated in a seriesextending from 100 grs. to more than 100,000 grs.,or the limit of saturation of the magnet. Two sets 192 DAVIS S MANUAL. of screw-cups will be seen on the board; one of theseis connected with a short coil round the magnet, theother with a long coil. By making this long coil offine wire, the instrument compares currents differingin their intensity. Two batteries are first estimated,as to quantity, by their magnetizing power throughthe short coil. Their rel
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
