Part 231

In 1901 the English Admiralty gave orders to the firm of Vickers, Maxim & Sons, of Barrow, to construct five of the _Holland_ type and subsequently several were constructed for the United States government.

To France belongs the credit of making submarine boats a real factor in naval warfare. In 1881 M. Goubet designed a small submarine boat, and in 1885 an improved _Goubet_, which was sixteen feet five inches in length, the motive power being electricity. Successful experiments led the French Admiralty to have the _Gymnote_ constructed at Toulon in 1888; she was fifty-six feet five inches long, with a displacement of thirty tons, her motive power being electricity stored in accumulators, which gave her a radius of thirty-two miles at eight knots. Her trials decided the French authorities to have more vessels built, and by 1901 there were some eleven completed.

In America, the _Hollands_ have been similarly improved, but other types are also in use. The _Lake_ type, named after the inventor, Simon Lake, contains an air-lock through which divers may emerge. These vessels have been adopted by Russia.

Germany started with _Hollands_, which they have developed along their own lines. The submarine boat is found in all navies now, and has proved an enormously efficient craft; displacements of one thousand tons are not unusual and speeds as well as radius of action have shown great improvement. The Diesel engine has been largely responsible for this. In manœuvers the craft have come up to expectation completely, the experience in actual war has shown them to be among the most formidable of war craft.

There are two distinct types of submarine vessel--the submarine proper, and the submersible. The submarine sinks through the exhaustion of all its buoyancy, and she sinks at once; the submersibles are forced under.

The latter, though equipped to travel on the surface of the water, are specially equipped for sinking quickly out of sight as the occasion arises. The most improved types, such as the recent German U-boats, have lofty armor plated conning towers, torpedo tubes, mounted guns, periscopes, and wireless equipments.

While in the present European war the submarines have shown themselves to be formidable weapons in skillful hands, they are not so formidable as to ring the death-knell of the large battleship, still less perhaps of the swift battle cruiser. Victory has usually rested with the more powerful ship and the heavier guns.

The present-day submarine suffers from two serious drawbacks: (1) inability to see under the water; (2) inefficient speed--the latter being much slower compared with the speed of fast surface boats. The chief chance of a submarine attacking an enemy with success is to come upon him unawares.

The periscopes and other optical tubes with which submarines are fitted, suffer also from many disabilities; and the fact that many collisions have occurred while using them, shows that they are not yet perfect. Obviously one showing not only what is forward of the submarine but what is on the surface of the water on every side is best. One of the drawbacks from which they suffer is the encrustation of salt on their reflecting surfaces; and small though the exposed surface of the periscope may be, there is always the chance of a vigilant enemy detecting it.

THE SUBMARINE IN PEACE.--It is pleasant to record that this invention, like many others of its kind, has not been devoted solely to war, but that peace also can claim its services. The recent remarkable trans-Atlantic voyages of the German submarine _Deutschland_ to American ports is an illustration of their importance to commercial transportation under critical conditions. Since, too, the submarine can sink or dive down to moderate depths, it is obvious it can be used for purposes of underwater salvage, construction, and exploration.

As an aid in the construction of breakwaters, the blowing-up of submerged wrecks in comparatively speaking shallow waters, in searching for sunken treasures, and as an aid to marine explorations in suitable waters, the peace or working submarine is likely to be of untold value.

ELECTRICITY AND MAGNETISM

WHAT IS ELECTRICITY? -- MEANS OF EXCITING ELECTRICITY -- ELECTRIFIED AND NON-ELECTRIFIED BODIES -- CONDUCTORS AND NON-CONDUCTORS OF ELECTRICITY -- ELECTRICAL MACHINES -- POSITIVE AND NEGATIVE ELECTRICITY -- VELOCITY OF ELECTRICITY -- PRINCIPAL AGENTS IN NATURE EXCITING ELECTRICITY -- LIGHTNING -- THREE FORMS OF LIGHTNING -- SHEET AND HEAT LIGHTNING -- DURATION OF A FLASH OF LIGHTNING -- PLACES DANGEROUS IN A THUNDER STORM -- HOW A TREE INFLUENCES LIGHTNING -- LIGHTNING CONDUCTORS -- THEIR PROPER PRINCIPLE OF CONSTRUCTION -- FRANKLIN’S EXPERIMENT WITH A KITE -- IDENTITY OF LIGHTNING AND ELECTRICITY -- UTILITY OF LIGHTNING-RODS -- WHAT IS THUNDER? -- WHAT OCCASIONS THE ROLLING OF THUNDER? -- AURORA-BOREALIS -- EXTENT OF THE AURORA -- HEIGHT OF THE AURORA -- APPEARANCE -- AURORA-BOREALIS OCCURS IN THE DAY-TIME -- WHAT IS GALVANISM? -- HOW GALVANIC ELECTRICITY WAS DISCOVERED -- CONSTRUCTION OF A GALVANIC BATTERY -- ORIGIN OF THE TERM “GALVANISM” -- POLES OF A BATTERY -- MEANS BY WHICH GALVANIC-ELECTRICITY IN QUANTITY CAN BE DEVELOPED -- DIFFERENT FORMS OF GALVANIC BATTERIES -- LIGHT AND HEAT PRODUCED BY GALVANISM -- PRINCIPLES AND PROCESSES OF ELECTRO-METALLURGY -- MAGNETISM -- NATURAL MAGNETS -- WHERE FOUND -- BODIES CAPABLE OF BEING MAGNETIZED -- INDUCTION -- MAGNETIC NEEDLE -- THE MAGNETIC COMPASS -- DISCOVERY AND FIRST USE OF THE COMPASS -- ELECTRO-MAGNETISM -- WHEN AND HOW DISCOVERED -- HOW IRON BARS BECOME MAGNETIC -- HORSE-SHOE MAGNETS -- EXCITATION OF MAGNETISM -- MORSE’S MAGNETIC TELEGRAPH -- TELEGRAPH, MAGNETIC, PRINCIPLES OF -- INTELLIGENCE, HOW CONVEYED BY -- ELECTRIC DYNAMO AND MOTORS -- WIRELESS TELEGRAPHY -- WIRELESS TELEPHONE -- X-RAYS

ELECTRICITY

_How may electricity be called into activity?_

By _mechanical power_, by _chemical action_, by _heat_, and by _magnetic influence_.

_What is the most ordinary way of exciting electricity?_

By _friction_.

_Do we know any reason why the means above enumerated should develop electricity from its latent condition?_

We are _entirely ignorant_ upon this subject.

_When you rub a piece of paper with India-rubber, why does it adhere to the table?_

Because the _friction_ of the India-rubber against the surface of the paper develops _electricity_, to which this adhesiveness is mainly to be attributed.

_Does electricity present any appearance by which it can be known?_

No; electricity, like heat, is in itself _invisible_, though often accompanied by both _light_ and _heat_.

_When a substance, by friction or by any other means, acquires the property of attracting other bodies, in what state is it said to be?_

It is said to be _electrified_, or _electrically excited_; and its motion towards other bodies, or of other bodies towards it, is ascribed to a force called electric attraction.

_Does an electrified body exercise any other influence than an attractive one?_

It _does_; for it will be found that light substances, after _touching_ the electrified body, will _recede from it_ just as actively as they approached it before contact. This is termed _electric repulsion_.

Thus, if we take a dry glass rod, rub it well with silk, and present it to a light pith ball, or feather, suspended from a support by a silk thread, the ball or feather will be attracted towards the glass. After it has adhered to it a moment, it will fly off, or be repelled. The same will happen if sealing-wax be rubbed with dry flannel, and a like experiment made; but with this remarkable difference, that when the glass repels the ball, the sealing-wax attracts it, and when the wax repels, the glass will attract. These phenomena are examples of _electrical attraction_ and _repulsion_.

_What is a non-electrified body?_

One that holds its own natural quantity of electricity _undisturbed_.

_What happens when an electrified body touches one that is non-electrified?_

The electricity contained in the former is _transferred_ in part to the latter.

Thus, on touching the end of a suspended silk-thread with a piece of excited wax, the silk will be excited, as will be shown by its moving towards a book, piece of metal, or any other object placed near it.

_Do all bodies conduct or allow electricity to pass through them equally well?_

Although there is no substance that can _entirely prevent_ the passage of electricity, nor any that does not oppose _some resistance_ to its passage, yet it moves with a much greater facility through a certain class of substances than through others. Those substances which facilitate its passage are called conductors; those that retard or almost prevent it, are called non-conductors.

_What substances are good conductors of electricity?_

The _metals_, _charcoal_, the _earth_, _water_, and _most fluids_, except oils, the _human body_, etc., are good conductors.

_What substances obstruct the passage of electricity, or are “non-conductors”?_

_Glass_, _resin_, _oil_, _silk_, _sulphur_, _dry air_, etc., etc., are non-conductors.

_What is an electrical machine?_

An electrical machine is an arrangement by which quantities of electricity can be collected and discharged.

One type of the electrical machine most usually employed consists of a large circular plate of glass, mounted upon a metallic axis, and supported upon pillars fixed to a secure base, so that the plate can, by means of a handle, be turned with ease. Upon the supports of the glass, and fixed so as to press easily but uniformly on the plate, are four rubbers; and flaps of silk, oiled on one side, are attached to these, and secured to fixed supports by several silk cords. When the machine is put in motion, these flaps of silk are drawn tightly against the glass, and thus the friction is increased, and electricity excited.

_Do we know what electricity is?_

No; a complete and final answer to this question is no more possible than the answer to the question--what is _life_? The _theory_ of electricity, however, opens up possibilities of the most fascinating nature; it gives us a wonderfully clear conception of which might be called the inner mechanism of electricity; and it even introduces us to the very atoms of electricity.

_Give a short outline of the theory of electricity._

EARLY THEORIES.--Early writers on the nature of electricity supposed it to be either a fluid of peculiar properties or else two fluids whose properties were complementary to each other or of opposite kinds; Franklin held the _one fluid_ theory. Later physicists arrived at the conclusion that whatever electricity might be, it was not a material substance. As an alternative it was suggested that electricity was a form of energy, but this proved untenable.

ELECTRON THEORY.--This, with certain reservations, is held by the scientific world of today. All matter is believed to be constituted of minute particles called “atoms,” whose diameter has been estimated at about one millionth of a millimeter. Up to a few years ago the atom was believed to be quite indivisible, but it has been proved beyond doubt that this is not the case. An atom may be said to consist of two parts, one much larger than the other. The smaller part is negatively electrified, and is the same in all atoms; while the larger part is positively electrified, and varies according to the nature of the atom. The small negatively electrified portion of the atom consists of particles called “electrons,” and these electrons are believed to be indivisible units or atoms of negative electricity.

The electrons in an atom are not fixed, but move with great velocity, in definite orbits. They repel one another, and are constantly endeavoring to fly away from the atom, but they are held in by the attraction of the positive core. So long as nothing occurs to upset the constitution of the atom, a state of equilibrium is maintained and the atom is electrically neutral; but immediately the atom is broken up by the action of an external force of some kind, one or more electrons break their bonds and fly away to join some other atom. An atom which has lost some of its electrons is no longer neutral, but is electro-positive; and similarly, an atom which has gained additional electrons is electro-negative.

THE ELECTRIC CURRENT.--A current of electricity is believed to be nothing more or less than a stream of electrons, set in motion by the application of an electro-motive force. Some substances are good conductors of electricity, while others are bad conductors or non-conductors. In order to produce an electric current, that is a current of electrons, it is evidently necessary that the electrons should be free to move. In good conductors, which are mostly metals, it is believed that the electrons are able to move from atom to atom without much hindrance, while in a non-conductor their movements are hampered to such an extent that interatomic exchange of electrons is almost impossible.

_Does electricity seem to exist in two different states or conditions?_

It does; and to designate these two conditions, the terms positive and negative have been employed. Thus a body which has an overplus of electricity is called positive, and one that has less than its natural quantity is called negative.

_Do light, heat, and electricity appear to have some properties in common?_

They _do_; each may be made, under certain circumstances, to _produce_ or _excite_ the other. All are so light, subtle, and diffusive, that it has been found impossible to recognize in them the ordinary characteristics of matter. Some suppose that light, heat, and electricity are all _modifications_ of some common principle.

_Why does the fur of a cat sparkle and crackle when rubbed with the hand in cold weather?_

Because the friction between the hand and fur produces an excitation of _positive electricity_ in the _hand_ and _negative_ in the _fur_, and an interchange of the two causes a spark, with a slight noise.

_Why does this experiment work best in very cold weather?_

Because the air is then _very dry_, and does not _convey away_ the electricity as fast as it is excited; if the air, on the contrary, were _moist_, the electricity would be _conducted off_ nearly as fast as it was excited by friction, and its effects would not therefore be so manifest.

_With what velocity is electricity transmitted through good conductors?_

With a velocity so great that the most rapid motion produced by art appears to be actual rest when compared to it. Some authorities have estimated that electricity will pass through copper wire at the rate of _two hundred and eighty-eight thousand miles in a second_ of time--a velocity greater than that of light.

_What agents are undoubtedly the most active in producing and exciting electricity in the operations of nature?_

The _light_ and the _sun’s rays_.

_Do some animals have the power of exciting electricity within themselves?_

There _are_ certain animals which are _gifted_ with the extraordinary power of _producing electrical phenomena_ by an effort of muscular or nervous energy. Among these the electrical eel and the torpedo are most remarkable.

_How powerful a charge of electricity can the electrical eel send forth when in full vigor?_

Sufficient to _knock down a man or stun a horse_.

_Is the electricity generated by these animals the same as that occasioned by the ordinary electrical machine?_

It _is the same_, and produces the _same effects_.

_Do vital action and muscular movements in man and animals give rise to electricity?_

They _do_; and it can be shown by direct experiment that a person cannot even _contract the muscles of the arm_ without exciting an electrical action.

_Does change of form or state in bodies generally produce electrical excitation?_

Change of form or state is one of the _most powerful methods_ of exciting electricity.

Water, in passing into steam by artificial heat, or in evaporating by the action of the sun or wind, generates large quantities of electricity. The crystallization of solids from liquids, all changes of temperature, the growth and decay of vegetables, are also instrumental in producing electrical phenomena.

_What is lightning?_

Lightning is _accumulated electricity_, generally discharged _from the clouds_ to the earth, but sometimes from the earth to the clouds.

_What causes the discharge of an electric cloud?_

When a cloud _overcharged_ with electric fluid approaches another which is _undercharged_, the fluid rushes from the former _into the latter_, till both contain the _same quantity_.

_Is there any other cause of lightning besides the one just mentioned?_

Yes; sometimes mountains, trees, and steeples will discharge the lightning from a cloud floating near, and sometimes the electricity passes from the earth into the clouds.

_How high are the lightning clouds from the earth?_

Sometimes they are elevated _four or five miles high_, and sometimes actually touch the earth with one of their edges; but they are rarely discharged in a thunder storm when they are more than seven hundred yards above the surface of the earth.

_What is a thunder storm?_

The _disturbance_ caused in the _air_ when successive discharges of accumulated electricity take place.

_Into how many kinds has lightning been divided?_

_Three._

_What are they?_

The _zig-zag lightning_, _sheet lightning_, and _ball lightning_.

_Why is lightning sometimes forked?_

Because the lightning cloud is at a _great distance_; and the _resistance of the air_ is so great that the electrical current is diverted into a zig-zag course.

_How does the resistance of the air make the lightning zig-zag?_

As the lightning condenses the air in the immediate advance of its path, it flies from side to side, in order to pass where there is the _least resistance_.

_Why is the flash sometimes quite straight?_

Because the lightning cloud is near the earth, and as the flash meets with very little resistance, it is not diverted; in other words, the flash is straight.

_What is sheet lightning?_

Either the reflection of distant flashes not distinctly visible or beneath the horizon, or else _several flashes intermingled_.

_What other form does lightning occasionally assume?_

Sometimes the flash is _globular_, which is the most dangerous form of lightning.

_Does a discharge produce a flash when it passes through good conductors?_

It _does not_, but passes quietly and invisibly.

_What is heat lightning?_

Sometimes it is the _reflection_ in the atmosphere of the lightnings of storms _very remote_, the storms themselves being so far distant that their thunders cannot be heard. This phenomenon is also occasioned by the play of silent flashes of electricity between the earth and the clouds, the amount of electricity developed not being sufficient to produce any other effects than the mere flash of light.

_Why is lightning more common in summer and in autumn than in spring and winter?_

Because the heat of summer and autumn produces _great evaporation_, and the conversion of _water into vapor_ always develops _electricity_.

_How long is the duration of a flash of lightning?_

Arago has demonstrated that it does not exceed the _millionth part of a second_.

_With what velocity is lightning, or the electric fluid which gives rise to its appearance, supposed to move?_

Not less than _two hundred and fifty thousand miles per second_.

_By whom was the identity of lightning and electricity first established?_

By _Dr. Franklin_, at Philadelphia, in 1752.

The manner in which this fact was demonstrated, was as follows:

Having made a kite of a large silk handkerchief stretched upon a frame, and placed upon it a pointed iron wire connected with the string, he raised it upon the approach of a thunder storm. A key was attached to the lower end of the hempen string holding the kite, and to this one end of a silk ribbon was tied, the other end being fastened to a post. The kite was now insulated, and the experimenter for a considerable time awaited the result with great solicitude. Finally, indications of electricity began to appear on the string; and on Franklin presenting his knuckles to the key, he raised an electric spark. The rain beginning to descend, wet the string, increased its conducting power, and vivid sparks in great abundance flashed from the key.

_Why was the kite insulated when Franklin fastened the key to the post with a silk ribbon?_

Because the silk was a _non-conductor_, and would not allow the electricity received upon the kite to pass off by means of the string to the ground.

_Was this experiment one of great danger and risk?_

It was; because the whole amount of electricity contained in the thunder cloud was _liable to pass from_ it, by means of the string, to the earth, notwithstanding the use of the silk insulator.

_Have we any proof of the utility of lightning rods?_

The experience of a hundred years has shown that when all the _necessary rules_ have been _observed_, the protection is perfect, as far as human effort can avail.

_Is a building more or less liable to be struck when furnished with a good lightning conductor?_

Lightning conductors do _not_, as many suppose, _attract the lightning toward the building_ on which they are situated; they simply _direct its course_, and _facilitate_ the _passage_ of the _fluid_ in the most direct way to the earth, only when a discharge must inevitably occur. There is no attraction, but the lightning takes the road which offers the least resistance.

_What is thunder?_

It is a certain _noise_ proceeding apparently from the clouds, which usually follows, after a greater or less interval, the appearance of a flash of lightning.

_How is it supposed to be occasioned?_

The usual explanation offered is a _sudden displacement of the air_ produced by the electrical discharges in which the lightning is evolved.

Others have supposed that the passage of the electric current creates a vacuum, and that the air rushing in to fill it produces the sound. Any explanation that has yet been offered is not altogether satisfactory.

_What occasions the rolling of the thunder?_

It has been ascribed to the _effect of echo_; but the true cause probably is, that the sound is developed by the lightning in passing through the air, and consequently separate sounds are produced at every point through which the lightning passes.

_Why is thunder sometimes one vast crash?_

Because the lightning cloud is _near the earth_; and as all the vibrations of the air (on which sound depends) reach the ear at _the same moment_, they seem like one vast sound.

_Why is the thunder generally heard several moments after the flash?_