Identifier: s4philosophicalm22lond (find matches)
Title: The Philosophical magazine; a journal of theoretical, experimental and applied physics
Year: 1798 (1790s)
Authors:
Subjects: Physics
Publisher: London Taylor & Francis (etc.)
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: University of Toronto

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source of great annoyanceto me; and for a time I almost despaired of obtaining pure cop-per wire. I knew that Professor Magnus had succeeded in ob-taining it for his galvanometer, but thd labour of doing so wasimmense*. Previous to undertaking a similar task, the thoughtoccurred to mc, that for my ))urpose a magnet furnished animmediate and perfect test as to the (juality of the wire. Purecoj)per is (liamaynvtic; hence its repulsion or attraction by themagnet would at once declare its titn(!ss or unfitness for the pur-pose which 1 had in view. Fragments of the wire first furnished to me by M. Sauerwaldwere strongly attracted by the magnet. The wire furnished byMr. Jiecker, when covered with its green silk, was also at-tracted, though in a nnich feebler degree. I then removed the green silk covering from the latter andtested tlie naked wire. // was rcjielled. The whole annoyance♦ PogK. Ann. vol. Ixxxiii. p. jH!); nnd Phil. Maf?. 1H62, vol. iii. p. 82. nu..^\ja£,. heT.4.Vo:.22JT.iZZ:
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Radiation of Heat by Gases and Vapours. 171 was thus fastened ou the green silk; some iron corapound hadbeen used in the dyeing of it; and to this the deviation of myneedle from zero was manifestly due. I had the green coating removed and the wire overspun withwhite silk, clean hands being used in the process. A perfectgalvanometer is the result. The needle, when released from theaction of a current, returns accurately to zero, and is perfectlyfree from all magnetic action on the part of the coil. In factwhile we have been devising agate plates and other elaboratemethods to get rid of the great nuisance of a magnetic coil*, themeans of doing so are at hand. Nothing is more easy to befound than diamagnetic copper wire. Out of eleven specimens,four of which were furnished by Mr. Becker, and seven taken atrandom from our laboratory, nine were found diamagnetic andonly two magnetic. Perhaps the only defect of those fine instruments with whichDu Bois Raymond conducts his admirable research

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