Lectures on electricity / by James Ferguson, F.R.S.

  • James Ferguson
Date:
1825
Catalogue details

Licence: Public Domain Mark

Credit: Lectures on electricity / by James Ferguson, F.R.S. Source: Wellcome Collection.

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    reach a very little way within the water, is inserted the wire communicating with the inside of the jar, through the other cork is inserted another wire, also just reaching into the water, and projecting a little externally above the cork. The jar being placed upon a table on which some gunpowder is laid, and the glass tube held vertically, at a little distance from the jar, with its lower wire among the gunpowder, on making the dis- charge, the electric fluid has to pass to the outside of the jar through the water and along the table, and the water and table being both imperfect conductors, the gunpowder lying between them is fired by the force of the stream. To melt Wires. To melt wire by means of electricity, the wire should be attached by one end of the hook communicating with the inside coating of a battery, and the other end fastened to one limb of the discharging rod; then when the battery is charged, the circuit may be completed with safety and convenience. Thirty square feet of coated surface will fuse the greater part of two feet of wire one-liftieth of an inch in diameter. If the power of the battery be very considerable, the melted metal will be dispersed and totally lost. If a wire be kept stretched, while it receives a shock just sufficient to make it red-hot, it will be lengthened by the operation ; but when the wire is not stretched, and the power of the battery is insufficient for its fusion, it is often shortened by the explosion. VanMarum shortened a wire eighteen inches long, and one fifty-third of an inch in diameter, a quarter of an inch at a single discharge. The facility with which metals are fused by electricity is not the same as that of their fusibility by fire. Van Marum caused wires of different metals to be drawn