Electricity for public schools and colleges (1891)
Larden, W. (Walter), b. 1855 or 6 · London : Longmans · leaf 47
centreof this graduated circle is called O. Above the mirror is sus-pended (when the instrument is used in magnetism) a magneticneedle a b, in such a way that its axis of suspension is immediatelyabove the centre O of the graduated circle. By looking down from above we can tell over what degree… … CH. III. MAGNETIC AIEASUREiMENTS 21 The needle is suspended by a fine wire or thread of glass, sohung that its prolongation would pass through O, the centre of thegraduated circle. This thread is fixed at its upper end to a brass piece ed (calleda torsion head) that caps the glass tube shown. This…
Electricity
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