H. S. Norrie

“ The zinc combines with the chlorine of the solution, liberating free hydrogen and ammonia. The hydrogen appears at the carbon, where it is acted upon by the oxygen of the peroxide of manganese. If too much current is taken from the cell, that is, if the wire or circuit be of too low resistance, the oxidizing action of the peroxide is not rapid enough, and a film of hydrogen, which is a poor conductor, forms over the carbon and increases the resistance of the battery—also setting up what is termed “local action” (actually, a battery opposing a battery) . ”

“ For automobiles or where the apparatus is subject to jar, a heavy iron vibrating armature would become unreliable by reason of its inertia and its responding to shock. At every jolt of the vehicle it would jar and get out of rhythm, and it certainly seems preferable to use a mechanical contact apparatus whenever feasible. In the older type of gas engine the spark is made by mechanism breaking contact right in the vapor. ”

“ The veriest tyro in electrical operations knows that electricity will cause a spark, and most persons are aware that the spark possesses considerable deflagratory powers, varying with the character of the spark. In electric gas lighting a spark of the proper character is passed across a jet of gas and ignites it. Sparks can be produced by various means: friction, battery current, induction either galvanic or electro-magnetic, by a Wimshurst or Toepler Holtz machine, or an induction coil operated by a battery. ”

“ In actual practice, when the wire is run through the paraffin bath not more than 50 per cent of the calculated wire will occupy the space. And the thickness of the paper rings must also be added when figuring the total length of the coil. In the iron-clad transformers or induction coils of highest efficiency used in the alternating current electric light system, the rule for determining the windings of the coils is based on the ratio of the turns of wire in the primary to the turns in the secondary, the electromotive force in the primary, and the lines of force cut by the windings. ”

“ In fitting a house with electric lighting burners, the question of selection is best solved as follows: For the main hall and foot of the cellar-stairs, use the automatic burner. For other hallways, dining-room, drawing-room, and bathroom use ratchet burners which turn on and light gas when chain is pulled. For bedrooms use plain pendant burners; automatics and ratchets add an element of danger, in that they may not turn off gas, or may leak. ”

“ A coil much used for electric baths has a primary winding only, regulated by the sliding in and out of the iron core, which necessitates the use of an independent vibrator, or else by varying the current strength with a rheostat. The general directions given before will answer in the present case, the only data necessary being the size of wire, which should be about six to ten layers of No. 20 B & S. The coil with movable secondaries here comes into service. Strong currents are needed for bath work, and any variety of winding can be used with this make of coil. ”

“ The wire used to connect the burners is generally bare, although an insulated wire is sometimes used. But the electromotive force of a 2-inch spark is so high that it is better to run the wires so they do not come near anything liable to cause a leak. The remarkable tendency of these high-tension currents must be most carefully guarded against; indeed, it is what makes this style of gas lighting so often unsuccessful. A damp wall, gilt wall-paper, a gas pipe hidden in the plaster, will often lead off the current. ”

“ A brass or copper disk 3 inches or more in diameter and upward of 1⁄2 inch thick has its periphery divided by a number of saw cuts, which divisions are often filled in with plugs of hard rubber or fibre. This disk is mounted on a shaft, which latter is either the shaft of an electro-motor, or is provided with a pulley by which it can be rapidly rotated. A strip of spring copper on each side of the disk presses upon the toothed surface, one strip being connected to the coil and the other to the battery or other current source. ”

“ For energizing a gas lighting primary coil, the current must be large, but is only required occasionally, the battery standing idle for long periods. In this case the class called open circuit cells are preferable, as they contain no strong acids and do not deteriorate to any extent when not in use. Of such class is the Leclanche-Samson, Monarch, carbon cylinder, and most so-called dry cells. As the resistance in a conductor [Pg 81] affects the current flow, so it does in a battery cell; the internal resistance of a battery is determined by its size, proximity of the elements, etc. ”

“ If an incandescent-lamp bulb be held in the hand and one end be brought near to a terminal of the coil, a beautiful bluish light appears.2 The carbon filament, if long, and not held by its loop, becomes electrified and oscillates, often giving out a clear, high, bell-like sound as it strikes the glass. Particles of carbon deposited on the glass during the burning of the lamp, shown in daylight as a blackening deposit, generally show little sparks, like stars scattered over the inside of the globe. ”

“ If now a coil of insulated wire S be included in the circuit, Fig. 2, upon repeating the make and break of contact, [Pg 3] the sparks will be much increased. This arises from induction, each adjacent turn of wire acting upon its neighbor. To better understand the action of induction, we will consider the following examples: Fig. 3. A is a circuit in which is the battery cell B. C is a second circuit lying close to but well insulated from circuit A. G is a galvanometer in which a magnetized needle swings right or left each time a current is passed through a coil of wire encircling it. ”

“ In a simple glass tube having two wires carrying balls inserted through its ends, from which the air has been partially exhausted, the study of the changes shown by the passage of the spark is extremely interesting. Before the commencement of exhaustion no luminous effect can be discerned; at a low degree of exhaustion a luminosity appears between the ends of the wires, the negative pole being surrounded by a violet glow and a larger pear-shaped red discharge from the positive. An interval near the negative electrode is in darkness, widening as the exhaustion progresses. ”

“ Now when an ordinary pendant or ratchet burner is pulled, it only sends a momentary current through the coil, enough to magnetize the core, but not enough to attract the armature sufficiently long for the bell to ring. But if a short circuit or ground should occur, the armature is held against the contact long enough to cause the bell to ring and give warning. In some cases a constant ringing attachment is added, in which case the bell rings until some one stops it. ”

“ A small disc of wood laid in the bottom of the cell will prevent contact at the bottom. Molten pitch or a composition of pitch and rosin in the proportion of 6 to 1 is poured on top, so as to seal the cell. As gas is generated in the cell, a safety valve should be provided, either a piece of porous cane or a short length of hard rubber tube, inside of which have been placed a few strands of woollen thread. This class of cell is so cheap and so many forms are available for choice that it is rarely desirable to make one's own. They will not do for steady current, but only for intermittent work. ”

“ The flame from this gas is hotter than that of coal gas, and deposits so much more carbon that a slight modification is necessary in the construction of burners for it. The details can be readily seen on observation of a burner, being simply in the adjustment of the contacts and their operation. It is better, however, to use a larger coil and a stronger battery for gasolene gas lighting than would be needed for coal gas—say, 6 cells of Samson, or large-size New Standard dry battery and a 10-inch coil having about 4 pounds or more of wire on it. ”

“ Ordinary insulated wires are ineffectually protected by the rubber compounds used. Glass, mica, and better still, a large air gap are the only insulations that will serve, for the tremendous potential or voltage of the current must be carefully considered whenever insulation is necessary. The coil is better provided with a spring key in the primary circuit than a vibrator, it gives better control of the circuit and probably a larger and better spark. ”

“ This is a most ingenious device for opening a short circuit, depending on its action upon the sluggish movement of glycerine (Fig. 28) .
A sealed glass tube pivoted near its centre contains a portion of glycerine sufficient to considerably overbalance it and keep one end down. A soft iron armature is attached to this tube in such manner that each time a current flows through a pair of electro-magnets, the attraction of the armature causes [Pg 50] the tube to tilt and the glycerine flows along to the other end. ”

“ In automobile work, where a heavy strain is made upon the engine, as in climbing heavy grades, it has been found that a stronger spark gives surer results. This would indicate more battery current through the coil, and it is a wise precaution to have a few extra cells attached that can be 40switched on if necessary.
In constructing spark coils for gas engines particular care must be given to the contact breaker. In most types of gas or oil vapor engines it is absolutely necessary to have the spark pass with uniform regularity, and immediately and surely when required. ”

“ Cells with small zincs and porous cups are of high internal resistance, those with large sheet zincs and big carbon surfaces, of low internal resistance. As the primary coil used in gas lighting is never much over one ohm, a cell of low internal resistance should be selected. But as the wires leading to the burners must be taken into account, a number of cells should be used to produce enough electromotive force to overcome the added resistance. Now battery cells can be arranged in a variety of ways—in series for higher electromotive force, and in multiple—for greater current.
Fig. ”

“ Sheet lead is an efficient screen to the rays, and, if desired, a lead screen can be made, partially enclosing the apparatus, to protect the operator. But it must be large245 enough and far enough distant from the coil and tube to avoid any possibility of leakage of current or even inductive influence. In operating X-ray machines never attempt to alter connections or make adjustments other than at coil platinum screw or Crookes tube spark gap without first shutting off current. Remember that a very unpleasant shock can be easily obtained from touching the apparatus with only one hand. ”

“ The Electric Light possesses the great advantage over gas, in that it can be turned on or lighted from a distance. The customary means of igniting gas with a match or taper is both dangerous and often inconvenient. The inventive genius of modern times has evolved a means of lighting gas by electricity which is both reliable and easy of application. ”

“ As in the simple electromagnet, the proportions of diameter and length of the primary coil and core will determine its rapidity of action. A short fat coil and core will act much quicker than a long thin one. But on a short fat coil the outside turns would be too far removed from the intensest part of the primary field. A good proportion of core length is given in the following table:
The primary coil P consists of two or not more than three layers of insulated copper wire of large diameter, being required to carry a heavy current in a 2-inch spark coil, probably from 8 to 10 amperes. ”

“ In general wiring, use weatherproof office wire, or, better still, well-made electric light wire. For ordinary house work No. 16 B. & S. gauge is preferable; smaller wire means higher resistance and less current at burner. For braided office wire, No. 16 runs about 95 feet to the pound, No. 18 about 135 feet to the pound. The cheaper grades of wire without the patent finish or extra insulation are not worth using; sooner or later trouble will ensue, [Pg 37] and once a house is wired, it is no pleasant job to hunt trouble, especially if the wire was put on before the plaster. ”

“ The greatest danger in the operation of such a piece of apparatus will be the tendency of the high tension spark to wander where it is not wanted, and to take short but forbidden paths back to the coil. However, care and perhaps experiment will prove the remedy. It will be noticed by reference to Fig. 49 that a circle has been drawn almost bisecting two of the tube-holders. This circle represents a circle of danger, and where a thin material has been used for the disk, the disk may very well be reinforced by a piece of stouter card cemented on its face. ”

“ Fig. 24 is the detail of the wiring for the cellar automatic burner A, from the push P, and is so clearly shown as not to require further explanation.
The secret of success in gas-lighting work is careful wiring. The platinum tip of the vibrating rod is often bent, either by accidental blow or by the continual hammering against the tip on the collar. This often causes an open circuit when the lighting armature refuses to buzz. Again, soot will form, causing weak action owing to imperfect contact. ”

“ As the action of the battery proceeds, this amalgam forces its way into the pores of the element and keeps up so good an amalgamation of both copper rod and zinc that zincs can be used up to a point when the rising internal resistance makes it economy to throw them away, and absolutely no perceptible local action takes place in the cell upon continued open circuit. A preparation is furnished if desired, which forms a jelly of the electrolyte, making the cell readily portable. ”

“ This wheel is mounted on the stem of a valve which opens or shuts according to the point of rotation, and thus shuts off or admits the gas to flow up to the burner. One pull of the arm turns the gas on; at the same time the wipe spring touches the contact on burner collar, and the gas lights. A second pull and the wheel, rotating, turns off the gas. [Pg 12] In all burners of this class a spring is provided to carry the arm up and back into its original position ready for another pull. Some burners do not make contact when the arm flies back, thus saving battery current. ”

“ The positive of the cell is connected to the positive main.
In connecting storage cells to the mains the utmost care must be taken that the terminals are correctly attached. It happens in isolated plants that some change is made in the wiring or the switchboard, which reverses the current without warning being given to the battery charger. It is the safest way to test the polarity of the terminals of both battery and mains each time charging is commenced. For polarity tests see Chapter I. It is immaterial on which side of the battery the rheostat or similar device is placed. ”

“ Hertz caused electric waves to pass through space and become visible by sparks across an air gap in a wire ring situated at a distance from the source of energy. The apparatus used, and termed an electric resonator, is in principle similar to that of the wireless telegraph. The minute sparks instead of idly passing across the air gap are made to traverse a "coherer" (to be afterwards more fully described) . This "coherer" substantially consists of a resistance, preferably metal filings placed in series, with a battery and relay. ”

“ When the space is filled up to the level of the paper disks and the paraffin is hard, loosen the set screw, and removing the outside disk, the coil can be slipped off, or a slight warming will loosen it. Any number of these coils can be made, and there are the advantages in this mode of construction that a bad coil will not spoil the whole secondary, and that the wire can be obtained in comparatively small quantities. ”

“ Although the charging of a storage or secondary battery is by no means a difficult operation, yet it requires care, and one unaccustomed to the work will meet many slight difficulties which may seriously affect the results. Pre-eminently the best charging source is a direct current, constant potential electric-light circuit. The amount of current required varies according to the type and make of the cell, but we will select one of a capacity of 50 ampere hours for illustration. ”

“ It is absolutely essential that the diameter of contacts for all contact breakers should be as large as possible and their faces filed truly parallel to enable them to easily carry all the current required. One of the main causes of failure of coil is burning of the platinum point and platinum burr, the current being then materially reduced. Large sparks at point of rupture are often indications that the condenser is not working properly—perhaps has broken down or is not large enough. ”

“ The only advantage of the first method being a saving of time when a number of cells is being set up. This saving of time is often of consequence, as the longer the newly set-up cell is on open circuit, the more copper will be deposited on the zinc, which is highly undesirable. This is shown by the blackening of the zinc as soon as it is put in the solution, which blackening it is hard to prevent entirely. ”

“ The bright yellow line of sodium in the orange rays is found in nearly all spectra, owing to its extensive diffusion in the atmosphere.
Tesla has succeeded in producing electric waves of length approximating to those of white light, which appear to have very little heat. The ideal light is that which shows no heat and does not liberate noxious gases in the air, and were it not for its feeble luminosity, the light of the electric spark passing through a carbonic acid vacuum would approximate this most nearly. ”

“ Fig. 28 shows the details of a contact breaker to be attached to the coil head direct.89 It is often used on very small coils, which, together with a miniature dry cell, is slipped into a pocket case. An important detail in small coils is to use a contact breaker of sufficient size. Most of them are not large enough to stand ordinary usage, the adjusting screw is not of sufficient diameter and the thread soon strips. There is no reason why the adjusting screw, its platinum tip, and the pillar or lug which holds it should not be solidly built, it would certainly require less adjustment. ”

“ If a beam of light be transmitted132 through a prism of glass the rays are decomposed, and what is known as a spectrum is formed (Fig. 40) . The most generally observed spectrum is the rainbow. When the light from a flame in which is burning some suitable substance be transmitted through the prism, the color which predominates in the flame will predominate in its spectrum. The combination of a prism and tubes for observing these effects is a spectroscope (Fig. 41) . The short fat spark from the Ruhmkorff coil is most useful in this work. ”

“ The positive element is self-amalgamating zinc, which is free from local action. The electrolyte is dilute pure sulphuric acid. The potential is high, being 2.5 volts, and the internal resistance is 0.14 ohm. This cell belongs to a group which is midway between primary and storage, or secondary cells. Its construction is similar to the lead-zinc secondary cell, in place of which it may be used, it being easy to recharge an exhausted cell by passing a weak current through it in reverse direction, thus recharging the peroxide of lead grid and renewing the zinc and electrolyte. ”

“ As a matter of practice, there is no really dry cell; all so-called cells contain liquid held in suspension, and their output is limited to the amount of fluid. One of this type can easily be made in the following manner: A containing jar is made up of first-quality sheet zinc, the edges being joined by a turned seam and then soldered, the bottom of zinc being also soldered in. In soldering here, as actually in all such operations, be absolutely sure the edges of the metal are clean. ”