Wire gauze

“ If, when this is done, the needle is deflected fully, the injury is farther away from the testing end, and other trials must be made farther on, until the spot is discovered. Wherever the covering of the wire has been pierced for testing, it must be carefully recovered, finished off with Prout's elastic glue, or gutta-percha, and made quite sound. The connections with the earth plates very frequently give trouble, the wires corrode or become detached from the iron pipes etc., and then the circuit is broken. ”

“ Iron seems to be the most desirable material for guard wires because it gives the required mechanical strength and sufficient conductivity at a less cost than copper, aluminum, or bronze, and is easier to handle and less liable to break than steel. It was formerly the practice to staple guard wires to the tops of poles or to the ends of cross-arms, but it was found that the wire was more apt to rust and break at the staple than elsewhere, and in the better class of work such wires are now mounted on small insulators. ”

“ The insulated wires being drawn into them, any short circuit or heating of the wire cannot give rise to a fire, as it can only take place in the interior of a non-inflammable tube. A third system of electric light wiring is the safety concentric system, in which concentric conductors are used. The inner one, which is well insulated, consists of a copper-stranded cable. The outer may be a galvanized iron strand, a copper tape or braid, or a brass tube, and is therefore necessarily connected with the earth. ”

“ As a supply of electrical current for lighting will, in the near future, be as much a matter of course for laboratory purposes as a gas supply, I add the following note. To heat a tube round a scratch, nothing — not even the oxygas blow-pipe — is so good as a bit of platinum or iron wire electrically heated. If the crack does not start by considerable heating of the glass, stop the current, unwind the wire, and touch the glass on the crack either with a bit of cold copper wire or a wet match stem. ”

“ At the left, the bare lugs are shown; in the center the copper of the conductors is shown inserted into the lugs, and at the right the whole conductor is shown bent back, the metal of the lug catching over the insulation to keep it from fraying out. The wires feeding arc lamps are always asbestos covered and this covering fits loosely to the wire and must be held in some such manner. A stock of such lugs should always be carried, as the leading-in wires to arc lamps, using heavy currents, frequently burn off. ”

“ The wires should be attached with tie wires having an insulation equal to that of the conductor which it secures to the knob. The use of split knobs does away with the necessity of using tie wires. The conductors must be at least 5 inches apart and it is better to support them on separate beams when possible. Each wire must be encased in a piece of flexible tube at all switches, outlets, etc., and this piece of tubing should be sufficiently long to extend from the last insulator and project at least one inch beyond the outlet. ”

“ If a coherer is shut up in a complete metallic enclosure, waves cannot get at it, but if wires are led from it to an outside ordinary [Pg 35] galvanometer, it remains nearly as sensitive as it was before (nearly, not quite) , for the circuit picks up the waves and they run along the insulated wires into the closed box. To screen it effectively, it is necessary to enclose battery and galvanometer and every bit of wire connection; the only thing that may be left outside is the needle of the galvanometer. ”

“ As shown in fig. 638, a wire AX, of non-oxidizable metal, of high resistance and low temperature coefficient, passes over a pulley B mounted on the shaft C. The ends of the wire are attached to the plate E at its ends F and G, the wire being insulated from the plate at G. A spring H holds the wire in tension and takes up the slack due to the expansion caused by the heating of the wire when a current passes through it. ”

“ Underground cables, cables formed of rubber insulated wires, and interior wiring which is properly done, all may be considered to be wiring which is unexposed, that is, not exposed to foreign high potentials, discharges, sneak, or abnormal currents. All other wiring, such as bare wires, aërial cables, etc., should be considered as exposed to such hazards and a fuse should exist in each wire between its exposed portion and the central office or subscriber's instrument. ”

“ We have seen above that by this is determined the number of interruptions of the electric current of our apparatus by means of the membrane and the platinum strip. The iron wire must therefore give out the tone in the same height or depth as that which struck the membrane. Now since a very far leading of the electricity makes it suffer scarcely any weakening in proper apparatus, it is intelligible that one can make the tone which acts on the membrane at one place audible, by means of the iron rod, at any desired distance. ”

“ To remove cable armours, clamp the conductor firmly in the armour cutter and with a pair of cutting pliers back the armour off, one strip at a time, to the point of contact with the cutting edge of the tool. The vise for holding conduit takes all sizes. The conduit can be cut with an ordinary hacksaw. To protect the insulation against any possible injury while the wire is being drawn in, a soft metal bushing should be inserted in the end of the tube and secured permanently thereto by means of the bushing tool. ”

“ It is well to have 1⁄2 lb. of No. 24 or 25 for electro-magnets, current-detectors, etc., etc. 1⁄2 lb. of No. 30 will not be too much, if you make induction coils. If you handle your wire carefully, single cotton-covered will do. Double cotton-covered is better than single, but it costs more. Be careful not to injure the covering. (See below for splicing wire.) Look out for broken wire.
288. Splicing Wire. Fig. 125. Do not simply touch [Pg 140] two wires together and imagine that you have a good connection; a mere twist is not sufficient. ”

“ If the pins and cross-arm are entirely of iron, the total resistance of the path through them from wire to wire is practically that of the insulator surfaces. If the pins and cross-arm are of wood which is dry, they may offer an appreciable part of the total resistance of the path through them between the wires of a circuit; but if the wood be wet, its resistance is very much reduced. ”

“ In the main the causes which hinder a pulse committed to a cable are two: induction, and the electrostatic capacity of the wire, that is, the capacity of the wire to take up a charge of its own, just as if it were the metal of a Leyden jar.
Let us first consider induction. As a current takes its way through the copper core it induces in its surroundings a second and opposing current. For this the remedy is one too costly to be applied. Were a cable manufactured in a double line, as in the best telephonic circuits, induction, with its retarding and quenching effects, would be neutralized. ”

“ The piles of this equipment, waiting shipment in the Roebling storerooms, give proof that the satire of the cartoonist and the mockery of the funny writer cannot destroy an ancient faith.
The telephone and telegraph companies use uncountable miles of copper wire in line service and other miles in fine sizes for instrument coils and divers other functions. Electricity as an agent would be a halting cripple without wire. The dynamo would have little more utility than a washtub. Armatures, frames for which are formed from flat steel wire, are wound in the Roebling plant in impressive number. ”

“ The joints connecting these rubber covered wires and the cable conductors are spliced in the same manner as straight splices, the paper sleeves used being of sufficient diameter to be backed out of the way over the rubber insulation. When the splice is completed a brass shell threaded at one end to fit a female thread in the upper end of the brass base, is slipped over the end of the rubber covered wire and screwed into the base. ”

“ Many uses are made of the galvanic current by medical men. If the circuit of the pile is closed and we take a wire in each hand and break contact, a concussion will be felt in the joints of the arm and fingers, and a certain contraction of the muscles. The currents of electricity cause the shocks, and by a peculiar arrangement by which the circuit can be closed or broken at pleasure, a series of shocks can be sent through the body when it forms the connection between the poles of the battery. We give illustrations of a medico-galvanic machine. In fig. ”

“ When wire is wound by hand from a spool into a coil, or around a core, it soon becomes twisted and tangled. Make a winder. This will keep the wire straight and save much time.
APPARATUS 81.
Fig. 54.
108. Electro-Magnet. Fig. 54. Drive a nail into a board so that it will project about 3⁄4 of an inch. A soft, or wrought-iron, nail is best, but a short, thick wire-nail will do. If you do not have a thick nail, use an iron screw. Wind 3 or 4 layers of insulated copper wire around it, and fasten the bare ends of the wire down with bent pins. ”

“ In wiring new wooden buildings do not draw wires too tight; the wood may expand and either break wire or cause a weakening of the insulation. In wiring before the plaster is put on, always leave a good length free, so it will not be covered up by the plasterers.
The wire used on the gas fixture is of a special kind, being made for the purpose. It is made in two sizes, No. 22 and No. 24 B. & S. gauge, and with three windings of cotton, three outer layers of cotton and one of silk, or three windings of cotton which is soaked in fireproof preparation, and then wound with silk. ”

“ Where poles have heavy circuits and several cross-arms each it is sometimes desirable to attach a guy or strut beneath the lowest arm and also a guy close to the pole top. Galvanized iron or steel wire is the material best suited for guys, and the cable form has greater strength and is more flexible than solid wire. ”

“ The practice of pulling wires through conduit by means of a block and tackle is very objectionable. It is evident that if the wires be pulled in by the application of much force the insulation is very liable to become damaged; furthermore, much difficulty will be experienced in pulling them out again, especially in warm places where the heat tends to soften the lining of the conduit, and also the rubber covering of the wire. Powdered soapstone put in the pipe while the wires are being drawn in will lessen the friction and permit the wire to go in more readily.
795
Fig. ”

“ The coping fastened down, the binding posts are now screwed down in the sites previously marked out for them. Before they are screwed entirely down, the denuded portion of the proximal end of each wire is securely wound around the screw of the respective binding post, and the posts are then firmly screwed down, holding the proximal ends of the wires in place. Connection is now established between the binding posts and the head and foot electrodes respectively. The vertical grooves are now to be filled in with putty and painted over, care being taken to [14] keep the carbon free from paint. ”

“ Wires having figure 8 or elliptical grooved sections have been employed, and have the advantage of allowing the use of a mechanical clip ear which is clear of the trolley wheel. The ordinary round wire is usually supported by a gun-metal or gun-metal and iron ear grooved to fit the wire, which is soldered or sweated to it. In Great Britain the overhead conductors are required by the board of trade to be divided into half-mile sections. The wires on adjoining sections are connected by section insulators. ”

“ The conducting cords sold by instrument-makers are sometimes not insulated at all, and then they are quite useless, but they are more commonly composed of several strands of metallic wire of about the diameter of sewing thread, the whole enclosed in some silken or woollen material, and nothing can be better than these latter when quite new. Their disadvantages are that they become frayed after a little use, and are liable to be constantly out of order, causing interruptions in the current, while they will only fit one kind of machine. ”

“ The quantity of electricity transmitted is therefore less, and the comparative intensity of it is greater.
Another difficulty attending the use of insulated wires buried in the ground arises from a very peculiar condition of electrical conduction, that could scarcely165 have been anticipated. The wire, coated with gutta percha, and surrounded externally with water or with moist earth, becomes an elongated Leyden jar; the gutta percha representing the glass, the wire the inside coating, and the water the conducting surface outside. ”

“ At the same time a few poles can be pulled down in another place, and the wires cut, and the probability is that the engineers who repair the line will not discover the hidden interruption of the circuit until after they have restored the gap, and found that the wire is still cut somewhere else, and even then the place where the non-conducting substance is introduced will not be discovered until some time has been employed in carefully testing the line with the galvanometer. ”

“ Whatever gauge wire be selected, it must be carefully insulated, to avoid all chance contact with nails, staples, metal pipes or other wires. The best insulation for wires employed indoors is gutta-percha, surrounded with a coating of cotton wound over it, except only in cases when the atmosphere is excessively dry. ”

“ There is one extremely important point about this experiment with arcs: most fires that result from defective wiring are caused by the forming of arcs. You see, if two wires touch each other while the current is passing and then move apart a little, an arc is formed. And you have seen how intensely hot such an arc is. Two wires rubbing against each other, or a wire not screwed tightly to its connection, can arc. A wire broken, but with its ends close enough together to touch and then go apart, can cause an arc. And an arc is very dangerous in a house if there is anything burnable near it. ”