Cumming, Linnæus, b. 1843. [from old catalog] · New York, D. Van Nostrand · leaf 246
he magnetic sys-tem were absolutely astatic, anycurrent, however weak, would beshown by the magnets at oncesetting at right angles to thecoils. In practice there is neveran absolutely astatic system, butthe earths power is so much |weakened that the very weak cur-rent becomes sensible by a… … FiG. 143. 228 Electricity. [Book III. ated card to show the deflections, while the lower needleswings within the long flat coils shown below. The coils arecapable of rotation so as to bring the needle to the zero ofgraduation, which is also in the plane of the coils, and thelevelling screws on the…
Electricity
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