Identifier: davissmanualofma00davi (find matches)
Title: Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity
Year: 1854 (1850s)
Authors: Davis, Daniel
Subjects: Magnetism Electricity Electromagnetic Phenomena
Publisher: Boston : Palmer and Hall
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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ive construction is placedat the end of the telegraphic line, which moves anarmature by the galvanic power, sufficiently onlyto make contact between a platinum point and sur-face, which are in the circuit of another small bat-tery, immediately on the spot. This at once worksthe registering apparatus with great force, its cur-rent having to traverse only a few feet of wire in itspassage to the registering electro-magnet. 321. Axial Receiving Magnet.—In Pig. 136is represented a receiving magnet of a new con-struction. The movement is produced by the axialforce, an iron bar of the U form being drawn withina double helix, as described in ^ 289. The bent bar AXIAL RECEIVING MAGNET 201 is horizontal, but is so suspended that its own weightwithdraws it from the coils when the current isinterrupted. In the cut, the instrument is shownin connection with a local battery for igniting anexplosive charge in blasting rocks, or for submarineor otiier explosions. The loss of power by con- Fig, 136.
Text Appearing After Image:
duction, renders it difficult, with a moderate sizedbattery, to explode the charge by heating a wire ata considerable distance. In the arrangement heredescribed, the receiving apparatus is used to completethe circuit of a small battery in a protected positionnear the place where the explosion is to occur. 203 DAVISS MANUAL, 323. In the figure, the coils are placed horizon-tally, and the U-shaped iron bar, which moves inconnection with a vertical bar, suspended by an axisabove, enters them at M. The influence of thehelices is aided by an armature, as in Fig. 121. Theconnections of the single galvanic pair, seen in theforeground, are so made that its circuit is completedwhenever the vertical bar comes in contact with theplatinum point, A, immediately in front of it. Thistakes place as soon as the long battery circuit iscompleted by the operator at a distance, and theaxial magnet drawn into the coils. This instrument,even without the armature, is more sensitive thanthe receiving magnet o

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