Sectional View of Hydraulic Buffer and Running-out Presses of a 60-pounder GunSectional View of Hydraulic Buffer and Running-out Presses of a 60-pounder Gun
Finally, to make sure that these have been all got rid of, the water traverses a filter, and then it is for all practical purposes as soft as rain-water. Some people are frightened of this artificially softened water, on the ground that chemicals have been added to it, supposing, apparently, that when they use such water they are really employing a chemical solution. That is quite wrong, however, for the added chemicals, combining with the "hardness," form substanceswhich are quite easily extracted from the water altogether. If we liken the hardness to a number of pickpockets in a crowd, and the added chemicals to a number of policemen who come in to arrest the said pickpockets, finally leaving the crowd free from both pickpockets and policemen, we get a simple illustration of what takes place.
But almost equally important as the provision of pure water is the effective dealing with the drainage of a large town. Much offensive matter flows under the streets of our towns and cities, and if it is not to become a nuisance it must be scientifically dealt with.
Years ago the drains of London simply emptied themselves into the Thames, until, in 1864, two large drains were constructed, one on each side of, and approximately parallel with, the river, to intercept the old drains and to carry their contents to points many miles down towards the sea. Even that, however, by no means abated the evil, for it simply transferred it to a new place. The river was as foul as ever.
William Morris, inNews from Nowhere, pictures the catching of salmon in the Thames off Chelsea, while one of London's prominent citizens, referring to what was being done in the direction of purifying the river, jocosely promised the members of Parliament a little fly-fishing at Westminster. Equally remote, it is to be feared, from actual accomplishment, these two prophecies do certainly indicate the tendency of events, for science has enabled the authorities to relieve the long-suffering river of much of the pollution which they used to thrust into it.
The first great step was the introduction, in 1887, of a treatment in principle very like that just described for softening water. The liquid from the drains is gathered into large reservoirs, where chemicals are added to it, causing the heavier matter to be precipitated in the form known as "sludge."
The liquid portion, or "effluent," as it is called, which is left is discharged into the river just as the tide is ebbing, so that it is carried right away, and, being comparativelyinoffensive, it pollutes the river very little indeed. The sludge, on the other hand, is pumped into special steamers, which carry it down to a certain spot off the Thames Estuary, where they drop it into the sea. The currents at the particular spot chosen are such that none of it returns to the river.
For a similar purpose electrolysis has been employed. In this process the sewage is made to flow between two iron plates which are connected up to a source of electric current so that they form electrodes, while the sewage is the electrolyte. The current decomposes the liquid sewage, causing chlorine and oxygen to be deposited upon that plate which forms the anode. This deodorises and purifies the sewage, in addition to which iron salts are formed on the iron plates, the effect of which is to precipitate the solid particles. Thus the same result is achieved as when chemicals are used, the main difference being that instead of chemicals being added, they are produced by the passage of the current.
But, from the scientific point of view, the most interesting process of all is that in which bacteria or microbes are brought into the service. The fact is familiar to most people that there are certain minute organisms which cause terrible diseases. It is not so well known that there are still more of them whose action is extremely beneficent. The writer has seen these minute living things described in a popular book as "insects," but they really belong to a low order of plant life, and, as has been said in an earlier chapter, in spite of the lowliness of their status in the order of creation, they are able to accomplish certain chemical processes which baffle the cleverest men. They are particularly good, or some of them are at any rate, at forming compounds in which nitrogen forms a part. Further, they can be divided into two classes, the aerobic and the anaerobic. The former work best in air, while the latter need an absence of air while they perform their functions. After which preliminary explanation we can proceed to describe how they are induced to carry on this valuable work for mankind.
The sewage flows first of all into a tank from which light and air are excluded as far as possible. There the anaerobic microbes flourish and multiply, and in the course of their life work they convert the sewage into an inoffensive liquid. After an appropriate interval the liquid passes to filter-beds, where it trickles over and through beds of coke, the effect of which is to aerate it very thoroughly, whereby the aerobic microbes come into action, completing the good work, so that nothing is left except a clean, colourless and odourless liquid. Indeed it is more than that, for the microbes have turned the offensive matter into nitrogenous compounds which, as we have seen in a previous chapter, are the best fertilisers. Hence this effluent, if placed upon the soil, is of great value.
The advantage of this to towns which are not blessed, like London, with a broad river and the sea near at hand needs no explanation.
The bacteria necessary to carry on the process are always present in sewage, and after any particular plant has been in operation for a little while there results an accumulation of them, so that the process becomes more and more active as time goes on. Mechanical ingenuity has so arranged matters that a sewage disposal plant on this system can be made quite automatic, requiring little or no attention for months together, the raw sewage flowing in at one end, while the odourless, harmless effluent pours out at the other.
And, moreover, so powerful is the action of these beneficent bacteria that should disease germs come down in the sewage they soon destroy them. No chemicals are needed, for the bacteria replenish themselves. No sludge is left, everything being turned into the harmless effluent. And, it may be said once more, disease germs are destroyed. Of all the valuable inventions of modern times this is surely not one of the least.
Even as late as the time of the Crimean War guns, even the largest, were made of that extremely common material, cast-iron. In fact, so far as material went, there was no difference between a gun and a water-pipe.
It was the need for some material possessing strength comparable with that of steel combined with the ease of production of cast-iron which led Sir Henry Bessemer to experiment in the manufacture of steel. Out of those experiments came Bessemer steel and its near relative, Siemens steel, two materials of universal application at the present time, so that to the needs of the artilleryman we owe two inventions which have proved of infinite value in peace as well as in war.
If any particular piece of ordnance can be said to be the prime favourite with the English-speaking peoples, it is the big naval gun. With both British and Americans the navy takes pride of place; both nations are given to contemplating with pleasure the number of dreadnoughts which they possess, and the distinguishing feature of a dreadnought is the large number of big guns which it carries.
Of the latest of these gigantic weapons one may not speak, but much is already public property concerning the 12-inch gun which the originalDreadnoughtcarried, and which is probably followed in its general features by the still greater guns of the most recent ships.
A gun is spoken of by its "calibre," which means the inside diameter, or, to use another expression, the size of the "bore." So the "12-inch" naval gun is 12 inches in thebore. Its length is in some cases 45 calibres and in others 50 calibres. In other words, some are 45 feet long and others 50 feet.
Why the difference? someone may ask. The answer is that the longer ones are an improved type. The extra length gives longer range and harder hits, as is quite apparent after a little thought. The explosive "goes off" and forthwith commences to drive the shell towards the muzzle. So long as it is in the gun the shell is being pushed faster and faster, but so soon as it leaves the muzzle the pushing ceases and the shell is left to pursue its course with its own momentum. Therefore, generally speaking, one may say that the longer the gun the faster will be the speed of the shell as it leaves the muzzle, the farther will it go and the harder will be the blow at a given range.
Incidentally this explanation reveals the need for different kinds of explosive. The propellant whose function it is to drive the shell out of the gun is different from that with which the shell is itself filled. The former needs to act comparatively slowly, so that it may continue its pushing action during the whole time that the shell is travelling along the gun. It might be ever so powerful, but were its action too sudden it would simply tend to burst the gun, without imparting very much speed to the shell. On arrival at its destination, however, the shell needs to burst suddenly and violently.
Another interesting question arises at this point. Seeing how fast is even the slowest speed at which a projectile travels, how can it be possible to measure the rate at which a shell issues from one of these monster guns. Needless to say, it is electricity which makes a thing apparently so difficult really quite easy.
Near the gun is set up a frame with a wire zigzagging to and fro across it, in such a manner that when the gun is fired the shell is bound to cut the wire. Electric current is made to pass through this wire on its way to a suitable house in which are recording instruments, where it energisesa magnet and so holds something up. Now it is easy to see that as soon as the shell cuts the wire the current will stop, the magnet will "let go" and the "something" will drop.
At a certain distance farther on there is a second frame with wires upon it, through which passes a second current, which is also led to the instrument house, where it again operates a second magnet.
When the first magnet releases its hold it drops something, to wit, a long lead weight. When the second magnet lets go it permits a second weight to fall against the first and make a dent or scratch upon it. The longer the interval between the action of the two magnets the higher up upon the lead weight will the scratch be. The apparatus, in short, will register the distance fallen through by the lead weight between the breaking of the wire in the first frame and the breaking of the wire in the second frame.
Now a falling object, if only it has such weight that the resistance of the air is negligible, falls according to a well-understood law, which law it obeys with the utmost accuracy. Therefore the distance fallen by the weight between the passage of the shell through two points gives a very accurate record of the time taken to travel from one to the other. Of course several such frames can be used if desired in the same way.
But to return to the gun itself. It is not merely one piece of metal but several tubes beautifully fitted one inside another. Moreover, in the British gun at all events, between two of the tubes there is a space filled with "wire."
This wire is perhaps better described as steel tape, and is of the finest material for the purpose, flexible and tremendously strong. It is wound round and round one of the tubes until there are many miles of it on a single gun. It is wound tightly, too, by means of special machinery.
The purpose of the wire is to resist cracking. The solid steel tubes may crack, and, as is the way with all cracks, these will tend to grow longer and longer. The many turns of wire, however, will not crack. Even if a few turns shouldbreak, the damage will not spread, and the gun can probably go on as if nothing had happened.
The material of which these guns are made is nickel chrome gun steel. Steel is ordinarily an alloy of iron and carbon, but this metal also contains traces of nickel and chromium, which make it specially suitable for its special purpose.
Each of the tubes of which the gun is formed start as an ingot, a mere lump of metal, but roughly shaped. The requisite mixture is obtained in a furnace and the molten metal is run out into a mould. The ingot is heated again and pressed under enormous hydraulic presses until it is approximately the shape required. This pressing not only produces the desired shape, it also improves the quality of the metal.
The rough forging is then bored out, to make it into a tube. One is inclined to wonder why the ingot is not cast hollow to commence with, and so save the labour of boring it all out later. The explanation of this is that certain impurities are always present in the metal and these always gather together in the part which sets last. Now in a solid block or ingot it is clear that the centre is the part which will set last, and hence that is the part where the impurities will congregate. Then, when the centre part is all bored out the impurities are entirely removed.
The tube is shaped externally by being turned in a lathe.
The innermost tube is not simply smooth. There is a spiral groove, called the "rifling," running round and round, screw fashion, inside it. The purpose of this is to give the shell a spinning action which causes it to keep point foremost throughout its flight. But for this the shell would tend to turn over and over, resulting in uncertain and inaccurate flight.
The shell is a little smaller than the bore of the gun, but near its base it has an encircling band of soft copper, which band is a tight fit in the gun. The soft copper crushes into the "rifling," whereby the shell obtains its spinning action.
The large guns are mounted in pairs, each pair on a turntable, by the movement of which to right or left they are trained upon the distant target. The turntable is surrounded by a wall of thick armour and is covered by an iron hood or roof.
In addition to being turnable to right or left, there is, of course, provision for raising or depressing the direction in which each gun is pointing. They need always to point more or less upwards, and the particular angle depends upon the range or distance of the object aimed at. This is ascertained by range-finding instruments and communicated to the officers in the turrets, as the covered turntables are called. The guns are then elevated or depressed to suit the range.
Each gun rests upon a cradle which is itself fitted upon a slide. When it is fired it "kicks" backwards, against the force of a buffer of springs, or a hydraulic or pneumatic cylinder. Thus after each shot the gun moves backwards upon the slide, but the hydraulic apparatus brings it back again into position for firing almost instantaneously.
In naval guns all the movements, including that of the turntable, are by power, either hydraulic or electric, or a combination of the two. The loading is also by power.
The shells and ammunition are kept well down towards the bottom of the ship, under each turret. Lifts bring them up from there to a chamber just beneath the turntable, known as the working chamber. Here a small quantity only is kept, and that for as short a time as possible before it is sent up by other hoists straight to the guns themselves. The hoists are so arranged that, no matter how they may be elevated or depressed, the ammunition is delivered exactly opposite the breech, as the rear end of a gun is termed. Then a mechanical rammer pushes it straight in.
Rifles of Different Nations (See Appendix)Rifles of Different Nations(SeeAppendix)
The breech of the gun is closed by a beautiful piece of mechanism called the breech-block. It is really a huge plug which securely closes the end of the gun, a partial turn after it is in place fixing it firmly enough to resist allthe force of the explosion. Yet it can be freed and swung back upon hinges in a few seconds. At the same moment that it is opened a jet of air blows into the gun, clearing out all effects of the recent explosion.
The process of firing one of these guns may thus be summarised. The turntable is swivelled to right or left until the gunners, looking through the sights, which are really telescopes, see the object straight in front of them. Meanwhile the sights have been set according to the range—that is to say, they have been so set in relation to the gun itself that when they point directly at the target the gun will be pointed upwards at exactly the right angle for that range. The whole thing, therefore, gun and sights combined, is tilted upwards or downwards as may be necessary until the sights point directly at the object aimed at. Then at a signal the gun is fired by electricity. The shock causes the gun to slide backwards upon its supporting slide, but the buffers, having taken the shock automatically, return it to its position again; the aim is thus undisturbed and it is ready for the next shot. These enormous guns can be fired at the rate of one shot every fifteen seconds.
Field guns are in principle very similar to these, only, of course, they are much smaller and are mounted upon carriages, so that they can be quickly moved from place to place. It must be borne in mind, however, that there are in the case of land guns two distinct types. Field guns, like naval guns, fire straight at their target; howitzers or mortars fire upwards with a view to letting the shell fall on the target from above. The latter are, generally speaking, short, fat, stumpy guns, as compared with the long, slender field guns.
In the field all guns have to be loaded by hand. The elaborate system of hoists which enables the great naval guns to be loaded with such rapidity is obviously impossible. That has to be compensated for by the skill and quickness of the gunners themselves, and it is indeed astonishing to see with what deftness they can handle the heavy and dangerous projectiles.
With all guns, of whatever kind, range-finding is of the utmost importance. No projectile, however fast it may travel, really moves in a straight line. It must be fired more or less upwards in order to compensate for the downward pull of gravity. If the elevation be insufficient the shell will fall short; if it be too much it may go beyond the mark, or it may fall short, according to circumstances. Just the right elevation is absolutely essential for good shooting. And for that to be achieved the range must be known with the utmost possible accuracy.
There are various systems and instruments used for this purpose, but all depend upon the same principle. It is the principle underlying all surveying and all astronomy; indeed it is the only possible principle for measuring a distance when you cannot actually go and lay a measure upon it or by it.
It is based upon a peculiar property of a triangle. In the case of every triangle which has straight sides, if we know the size of two of the angles and the length of one of the sides we can easily calculate all that there is to be known about that triangle. We unconsciously use the principle when we judge a distance with our eyes. We focus each eye separately upon the object which we are looking at. In other words, each of our eyes looks along a straight line terminating in the object. Those two lines, together with a line joining our two eyes, form a triangle. The line between our eyes is the "base," the line of which we know the length, while the directions in which we point our eyes give us the angles at each end of the base. From this we are able to judge the distance of the object. Of course there is probably not one of us who knows the length of that natural "base" in inches, but that does not matter in this case, since it is always the same whatever we may look at, and so the mere inclination of the eyes gives us a means of comparing distances. When we judge by the eye alone, what we really do is to draw upon our experience and consciously or unconsciously compare the distance whichwe are estimating with some others which we already know.
In surveying, a telescope is set up at one end of a base-line and pointed first at the other end of the base-line and then at the distant object. A scale with which the instrument is provided gives us the size of the angle between the two. Then the same thing is done at the other end of the "base" and the similar angle there is obtained. The length of the base being known, the distance of the remote object can then be calculated.
In the same way two observations can be made, one at each end of a ship, the length of the ship forming the base-line. Or an instrument can be made by which two observations can be made simultaneously by the same man.
This is done by means of mirrors which are turned so that the same object is seen in both of them, apparently in a straight line. The extent to which one of them has to be turned gives the angle, and the instrument forms the base.
Anyone with the slightest geometrical experience will perceive at once that the best results are obtained when the base-line is of considerable length, and hence small portable range-finding instruments such as can be easily carried and used by one man are necessarily less accurate than an arrangement such as has been suggested above, where two observers work simultaneously from the two ends of a ship.
In many cases, however, the self-contained instrument is the only one which it is possible to use, and when the instrument is well made and in experienced hands the results are surprisingly good.
As used in surveying, for example, where the base-line may be anything, according to circumstances, and the angles may likewise vary at both ends, elaborate trigonometrical calculations have to be performed to arrive at the desired result. If, however, the base-line be always the same, and one of the angles be always a right angle, the distance of the distant object will vary with the remaining angle. Indeed the scale by which that angle is measured can bemade to give not degrees, but the distance of the object. Portable range-finders, therefore, in many cases have one reflector set for a right angle and only one of the reflectors movable. The instrument then shows the distance of the object at a glance.
This is impossible in the case of two separate observations on a ship. In that case the base is always the same, but since the ship cannot be set at right angles to the object whenever a range has to be found, both angles have to be measured. There is, however, a beautifully simple little mechanism in which two pointers are set one to each of the two angles, and the distance is then shown instantly.
The German Mausercan fire forty rounds a minute—more than any other rifle used in the war. The rifle is of the 1898 pattern, weighs 9 lb. 14 oz. with bayonet fixed, and is sighted from 219 to 2187 yards. The magazine holds five cartridges, packed in chargers. As the rifle is not provided with a cut-off, it cannot be used as a single-loader. With its long barrel and long bayonet it gives a stabbing length of 5 ft. 9 in.—8 in. longer than the British.
The Austrian Rifleis the Mannlicher. This rifle is very fast in action as a snap back and forth of the wrist is sufficient to operate it. It is, however, more trying for prolonged work, owing to the throwing of the strain only on the wrist. Without the bayonet the rifle weighs only 8 lb. 5 oz., the lightest of all, yet the bullet—244 grains—is the heaviest used by any of the belligerents. The rifle is sighted from 410 to 2132 yards, and the barrel has a four-groove rifling.
The British Lee-Enfield—Mark III—is the outcome of the South African War. It is not too long for horseback and is yet quite efficient for infantry. The barrel is 25 in. long and has five grooves in the rifling. It is sighted from 200 to 2800 yards. The rifle is fitted with a magazine which holds ten cartridges packed in chargers, each of which contains five rounds, so that the magazine is filled with ten rounds in two motions. The rifle is also fitted with a cut-off, which enables it to be used as a single-loader. It is altogether a most efficient weapon.
The French Lebelis of the 1886-1893 pattern, and with bayonet fixed is longer than any other rifle. It weighs, without bayonet, 9 lb. 31⁄2oz. The tube magazine under the barrel contains eight cartridges; it takes, of course, longer to charge than a magazine loaded with a charger. It does not fire as many shots a minute as some of the other rifles in the field. The position of the magazine is indicated by the crosses. The rifle is sighted from 273 to 2187 yards, and the bullet weighs 198 grains.
The Belgian Armyuses the 1889 pattern Mauser, which weighs just over 8 lb. and is sighted from 547 to 2187 yards. The magazine holds five cartridges carried in clips; not having a cut-off, the rifle cannot be used as a single-loader. It has four grooves in its rifling and measures 4 ft. 21⁄4in., or, with the bayonet, 4 ft. 113⁄4in. The bayonet is short and flat.
The "3 Line" Nagantof Russia is1⁄4lb. heavier than the British rifle and is over 7 in. longer. The triangular bayonet is always fixed and never removed from the rifle. The magazine of the rifle is of the box type and holds five cartridges. The rifle is capable of discharging twenty-four bullets to the minute. A useful feature is the interrupter, which prevents jamming of two cartridges.
The Italian Mannlicher-Carcanois of the 1891 pattern. It weighs, without bayonet, just over 8 lb. 6 oz. and measures 503⁄4in. The barrel, 303⁄4in. long, has a four-groove rifling. The box magazine, fixed under receiver without cut-off, holds six cartridges. The magazine holds six rounds, and the rifle is capable of discharging fifteen rounds a minute.
AAccumulators or secondary batteries,65Aerial craft experiments,202Aerobic and Anaerobic bacteria,234Afterdamp,228Alcohol as a fuel,49Alternating current,35,193Altofts, artificial coal mine at,139Aluminium,133Amalgam,117Ammeters,25Ammonia in making ice,72Ammunition for big guns,240Amperes,22,24Analysis and synthesis,43Anode,55Anschutz, Dr,96Antennæ,162,171Anthracene oil,48Arc, the, in wireless,165Argon, the gas,75Artesian wells,45"Atmosphere," a unit of measure,72Atoms,56"Avogadro's Constant,"33BBacteria, beneficent,234Ball mill, the,115Battery, electrical,23Benzine,45,48Bessemer, Sir H.,236Blowpipe, oxyhydrogen,120Board of Trade Unit, the,22Boiling water,10,76Bore of a gun,236Boulders, blasting,20Branly,166"Brattice cloth,"224Breech of a big gun,240Brennan torpedo, the,102Brewing,50"Brine" in machine-made cold,70"Budding" of yeast, the,51CCalibre of a gun,236"Capacity," 153Capacity and inductance, electrical properties,161Carbolic oil,48Carbon,11Carbonic acid gas,10Carburetter, the,46Cardiograms,32Caselli,176Cathode,55Cavendish, investigations of,73Cellulose,12,44Centrifugal tendency,115"Character" of a lighthouse,86Charge and current,32Cheddite,13Chemicals in waterworks,232Chemistry, organic and inorganic,42Chlorate of potash,12Chloride of soda,58Chronograph, the,141Clark's Cell,23Coal and oil,47Coal, burnt,10Coal-dust an explosive,10Coal-dust, explosions from,139Coal-pitch,48Coal-tar,48"Coasting" lights,80Coherer, the,103,162,167Coke in smelting,125Colliery explosions,137Colliery explosions, rescue apparatus,226Colours of the spectrum,213Colours of flowers,213Compass, a ship's,91Compressed air in torpedoes,100"Concentrates,"115Condensers in wireless,163Conservation of energy,132Contact makers,145Coronium, the gas,74Corundum,134Coulombs,23Courrières colliery disaster,221Creosote,48Creosote oil,48Crooks, Sir W.,33Crushing mills,115Crystal detectors,171Curie, M. and Mme.,33Curtis and Harvey,9Cyanide process, the,118Cyanogen,118Cymogene,45DDetectors,167Detonator, the,14Dextro-glucose,51Diamonds,135Diesel engines,46Direct-current electric motor,191"Dirt-auger," the,15Ditches, blasting,18Drainage,233Du Pont Powder Company,9Duddell, W. H.,37Dufay dioptichrome process,219Dynamite, what it is,9,12;in agriculture,13;firing a charge,16;fruit trees,16;marshy ponds,17;ditches,18;tree stumps,19;boulders,19;wells,20Dynamo, the,65EEddystone Lighthouse,80Edison's accumulator,66Einthoven, Prof.,30Electric arc, the,123Electric furnace,125Electric fuse, the,16"Electrical Inertia,"153Electrical battery,23;pressure,23;cells,23;measure,24;magnetism,25Electricity,22;the current,56;electro-plating,58;purification of metals,61;secondary batteries,62Electrode,55Electrolysis,55,170;in drainage,234Electrolyte,55Electrometer, the,32,34Electro-plating,58Electros,60Electroscope, the,34Endosperm, the,50Engines driven by oil fuel,46Enzymes,50Ether,45,149Ethyl alcohol,49Explosions,9;in mines,137Explosive link, the,104Explosives for guns,237F"Falls" in a coal mine,223Fermentation,50Fessenden, R. A.,169Field guns,241Filters in waterworks,232Fire-damp,137Firing-pin of torpedo,102Flashing lights,81Fog, effects of,82Fog signals,88"Fractional distillation,"76"Frequency,"36Frequency meter,193Friction clutch,195"Frue" vanner, the,116Fruit trees and dynamite,16Fuses, firing,20GGalvanometer, the,27,170"Gangue," the,112Gauges,208Gelignite,12Glycerine in explosives,11Gold,110Guiding lights,81Gyroscope, the,93,100HHalf-tone illustrations,181"Hard-pan,"14Harris, Sir W. S.,36HawkeandOlympic, collision between,198"Head" of the torpedo,99Heat and electricity,37Heat of the electric arc,123Heat, testing by,205Helium,33,75Hertz,154Howitzers,241Hughes, Prof.,159Humphrey Gas Pump,231Hydraulicing,112"Hydro-carbons,"45Hydrogen, liquid,73Hydrometer, the,65Hydrostatic valve of torpedo,101"Hyper-radial" apparatus,88IIce, machine-made,71Indigo, synthetic,44Inductance,154Induction coil for wireless,162Induction furnaces,129Insulating ink,177"Interference" of light waves,159Ionisation of the atmosphere,172Iron,109JJupiter's moons,150KKelvin, Lord,28Kerosene,46Kieselguhr,12Kilowatt, the,25Kinematograph in coal mine experiments,146Korn, Prof.,183Krypton, the gas,75LLeclanche cell, the,23Leyden jar, the,153Light, speed of,151Light waves,151Lighthouse, the,78Lighthouse lamp, the,83Limit gauges,209Liquid air,73Lodge, Sir O.,159,161Lumière autochrome process,216MMagnetic detector, the first,168Magnetic pole, the,90Magnetism,25Magnets,25"Making" light, the,79Maltster, the,50Mansfield Rescue Station, the,224Marconi,161Marshy ponds, to remove by dynamite,17Mash tun, the,50"Master compass," the,97"Master" records,60Maxwell, J. C.,152Measuring by electrolysis,62Mendeluff's table,74Mercury,114Metallographic testing,205Metals, testing,204Methane gas,10,124Methyl alcohol,49,53Microbes, their use,43Mine-laying,105Mine-sweeping,107Molecules,56Morris, William,233Mud, gold from,122Muirhead, Dr,167Murette or pedestal of lighthouse lamp,85NNaphtha,45National Physical Laboratory,199Natural frequency,161Neon, the gas,75Nickel chrome gun steel,239Nitric acid,11Nitro-cotton,12Nitro-glycerine,11Nitrogen gas,9Nobel, inventor of dynamite,12,135Nodes,157OOhm, the,22,24Ohmmeter, the,27Ohm's law,27Oil, mineral,44Oil-producing countries,47Optical apparatus of lighthouse,86"Orders" of lighthouse apparatus,88Ores,110Orthochromatic plates,212Oscillations, electrical,36Oscillatory circuit,154Oscillograph, Duddell's,39Oxide of iron,133Oxyacetylene flame, the,131Oxygen gas,10Oxyhydrogen jet,130PParaffin wax,45Patents,174"Periodicity,"36"Personal equation," the,207Petrol,45,52Petroleum,44Phonograph, the,60Plans of a ship,199Plates of the secondary battery,64Platinum,184Plumbago in plating,59Poulsen arc, the,173Poulsen, Valdemar,165Pressure gauges,143Priestly, investigations of,73Primary colours,213Prisms, reflection of,85Process blocks,186Projectiles, velocity of,237Propellers of the torpedo,99Propellers, testing aerial,203Prout's anonymous essay,74Prussiate of potash,177Purification of metals,62QQuadrant electrometer, the,35Quartz,113;fibre,31,131RRadium,33Ramsey, Sir W.,75Range-finding,240,242Rayleigh, Lord,74Receiving instruments for wireless,162"Record" vanner, the,116"Rectifier," the,37,171Red rays of light,82Reflection by prisms,84Reflectors, lighthouse,84Reiss electrical thermometer,36Repeated-impact testing machine,204Rescue teams for colliery accidents,221,222Resistance welding,126"Resonance," an experiment,160Reviving apparatus for coal mines,229Rheostat, the,188,191Rhigolene,45Rifling of a gun,239Rubber, synthetic,44Rubies, artificial,131Rudders of a torpedo,100Rutherford, Prof.,33,168SSaccharine,48Saltpetre,12Schwartzkopff torpedo, the,99Scilly Island lighthouse,80Sea, gold in the,120Secondary battery, the,62"Sectors,"81Selenium,184"Self-rescue" apparatus, a,228Shale, oil from,45Shells for guns,239Ships, testing by models,200Short circuit,179"Shunt," the,165Sighting a big gun,241Silica,133Skating rinks, ice in,71"Sludge" and "effluent" of drainage,233Spark detectors,166Spark-gap,162Spectrum, the,213Spinthariscopes,33Spirits,52Springs, testing,203Stamps for crushing quartz,113Starch grains in colour photography,217"Step-down" and "step-up" transformers,127"String galvanometer," the,30Submarine mines,104Submarine telephone,88Sulphuric acid,11,43Sunlight, composition of,213Synchronism, difficulties of,182,191Synthetic substances,44T"Tamping,"15Tank for testing at Teddington,201;New York harbour,201Telautograph, the,180Telectograph, the,180,185Telegraph key for wireless,162Telewriter, the,187Temperature, measuring,38Tesla, Nicola,164Testing by heat,205Testing machines,206Thermit,135Thermo-couple, the,38Thermo-galvanometer, the,37Thomson Mirror Galvanometer, the,28Thomson, Prof., S.,159Torpedo, the,98Training station at Porth,225Transformer, the,127Transmitting instruments,163Travers, Prof.,75Tree stumps, blasting,19Tuning-fork a standard of speed,193Turret of a battleship,240UUltra-microscope, the,209Ultra-violet rays,172VVarley and the Atlantic cable,28Vaseline,46Veins or lodes,113Vickers,202Voltmeter, the,26Volts,22,24WWater a source of heat,124Water, soft and hard,232Watt, the,24Waves caused by ships, recording,200Wax models of ships,199Welding by electricity,125Wells, blasting,20Welsbach mantle, the,124Whitehead,99Wire guns,238Wireless telegraphy,161,173Wireless torpedo, the,102Wood-meal in explosives,12Wood spirit,49"Working fluid," the,68YYeast,51ZZero,68Zinc in gold recovery,119