Page:Federal Reporter, 1st Series, Volume 1.djvu/314

 306 PEDEBAL EEPORTEB. �of the bar being regulated by a set-screw, makes a good oir- cuit-breaker, and will be found fuUy described by the said Charles G. Page in Silliman's Journal, volume 32, pages 356 to 358, in a communication dated April 19, 1837. This speeies is, however, not so simple as others, and further allusion to it is not necessary. A vibrating armature is preferable, as it requires no change of pôles to efifect its motion, this being produced by merely intercepting the galvanie current at snit- able intervais. One form of vibrating armature is shown at fig. 8. A small rod of soft iron, about the size of that shown in the figure, is mounted upon an axis or shaft, s, -which is supported in suitable bearings upon two pillars, r, so as to vibrate freely. A small electro-magnet is supported upon one of these pillars, and the armature is placed between its branches, so that one end is above and the other below the plane of the magnet. One end of the armature bears a branching copper wire, its branches passing down into mer- cury cups c, c'. Cup c may be partly of glass, so that the play of the end of the branch wire in and out of the mercury in the cup may be seen, and the spark produced on breaking the circuit rendered visible. When the magnet is charged the armature is attraoted towards its pôles, and around the ends of the armature is a ferrule of thin brass or non-mag- netic metal, to prevent magnetic adhesion of the armature to the magnet. The galvanie connections are under the base board and may be traced as f ollows : One pôle of the battery being connected with cup p, and the other with cup n, the current will pass along from cup p to cup c, as indicated by the arrow, thence upward through one branch of the wire and downward through the other branch into cup c'. thence upward again into one end of the wire around the electro- magnet, and, circulating around the wire coil, will pass out through the other end to cup n, and so back to the battery. The passage of the current charges the magnet, lifts one end of the armature, raises the branch wire from the mercury in the cups c, c', and breaks the circuit. This end then falls by its weight, the branch wire overbalancing the other end, the circuit is again completed, and thus it may be ��� �