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metals, in virtue of which electricity ing this, wrote to one of his friends in runs along them in preference to other Philadelphia :substances, and discovering the property of points to attract the electric “ The king's changing his pointed conHuid, Franklin proceeded at once to ductors for blunt ones is a matter of small the discovery of conductors, or "light

importance to me. If I had a wish about ning-rods," for the protection of

them it would be that he would reject them buildings. • If these things be so,"

altogether as ineffectual. For it is only since

he thought himself and his family safe from vrote he

the thunder of heaven that he has dared to “May not the knowledge of this power

use bis own thunder in destroying his innoof points be of use to mankind in preserving

cent subjects.”+ houses, churches, ships, &c., from the stroke of lightning, by directing us to fix on the Art often presses into its service the highest points of those edifices upright rods discoveries of Science, but it sometimes of iron made sharp as a needle, and gilt (at provokes them. Art surveys the fruit the points) to prevent rusting; and from the of the toil of the philosopher, and sefoot of those rods a wire down the outside of lects such as suits her purposes ; but the building into the ground, or down round

sometimes, not finding what is suitable one of the shrouds of a ship, and down her side till it reaches the water? Would not

to her wants, she makes an appeal to these pointed rods probably draw the electric

Science, whose votaries direct their fire out of a cloud before it came nigh

researches accordingly towards the enough to strike, and thereby secure us from desired object, and rarely fail to attain that most sudden and terrible mischief."** them.

One of the most signal examples of It is known to every one, that after the successful issue of such an appeal this Franklin established his theory by presents itself in the safety-lamp: the celebrated experiment of the kite, The same gas which is used for the by which he literally drained a cloud purposes of illumination ofour cities and of its lightning ; but what is not so towns (and which, as is well known, is well known is, that when the paper

obtained from coals by the process of written by Franklin, explaining his baking in close retorts) is often spon. project of constructing lightning-con- taneously developed in the seams of ductors for the protection of buildings, coal which form the mines, and collects was soon afterwards read before the in large quantities in the galleries and Royal Society of London, it was re- workings where the coal-miners are ceived with peals of laughter, and was employed. When this gas is mingled voted so absurd as to be deemed un- with common air, in a certain definite worthy of being printed in the “ Phi. proportion, the moisture becomes highlosophical Transactions.” It was, how- ly explosive, and frequently catastroever, printed by an independent pub. phes, attended with frightful loss of life, lisher, and has attained, as is well occurred in consequence of this in the known, a world-wide celebrity.

mines. The prevalence of this evil at Not long afterwards, the same length became so great, that governmembers of the Royal Society who ment called the attention of scientific laughed at Franklin's project, were men to the subject, and the late Sir called upon to superintend the erec- Humphrey Davy engaged in a series tion of conductors upon the royal pa. of experimental researches with a view lace, when, to gratify the royal spleen to the discovery of some efficient proagainst the rebellious philosopher of tection for the miner, the result of the revolted colonies, they rejected the which was, the now celebrated safety. pointed conductors recommended by lamp. Franklin, and actually caused blunt Davy first directed his inquiries to conductors to be placed on the palace. the nature and properties of flame. Franklin, who held the office of Ame- What is Alame? was a question which rican Minister in London (the inde. seems until then never to have been pendence of the United States being answered or even asked. then recently acknowledged), on hear- All known bodies, when heated to a

* “Franklin's Works," vol. v. p. 235. Boston: 1837.
† " Franklin's Works," vol. v. p. 227.

sun.

certain intensity, become luminous. or candle, instead of being as usual Thus iron, when its temperature is enclosed by glass or horn, was enclosed elevated first, gives a dull red light, by wire gauze of that degree of finewhich becomes more and more white ness in its meshes which experiment as the temperature is increased, until had proved to be impervious to flame. at length it becomes as white as the When such a lantern was carried into

Davy showed that gaseous sub- an atmosphere of explosive gas, the stances are not exempt from this law, external atmosphere would enter freely and that flame is nothing more than through the wire gauze, and would gas rendered white hot.

burn quietly within the lantern ; but He further showed that if the gas the meshes which thus permitted the thus rendered white hot be cooled, it cold gas to enter, forbid the white-hot will cease to be luminous in the same gas within to escape without parting manner, and from the same cause as with so much of its heat in the transit would be the case with a red hot poker as to deprive it of the character and plunged in water.

properties of flame; so that, although it He shewed that the gas which forms passed into the external explosive atflame may be cooled by putting it in mosphere, it was no longer in a condi. contact with any substance, such as tion to inflame it. metal, which, being a good conductor, The lamp thus serves a double purwould deprive it of so much of its calo. purpose : it is at once a protection ric that it must cease to be luminous. and a warning. It protects, because

Thus, if a piece of wire net-work, the flame within cannot ignite the gas with meshes sufficiently close, be held outside the lantern. It warns, because over the flame of a lamp or candle, it the miner, seeing the gas burning within will be found that the flame will not the lantern, is informed that he is enpass through the meshes. The wire veloped by an explosive atmosphere, will become red hot, but no flame will and takes measures accordingly to venappear above it.

tilate the gallery, and meanwhile to It is not, in this case, that the gas prevent unguarded lights from entering which forms the flame does not pass it. through the meshes of the wire, but in Nothing can be imagined more tri. doing so, it gives up so much of its umphantly successful than this investiheat to the metal, that when it escapes gation of Sir Humphrey Davy. Some from the meshes above the wire, it is philosophers have the good fortune to no longer hot enough to be luminous. arrive at great scientific discoveries in

Sir Humphrey Davy, in the re. the prosecution of those researches searches which he was called to make, to which the course of their labours discovered this important fact, which leads them. Some are so happy as to enabled him to explain the nature and make inventions of high importance in properties of flame; and having so dis- the arts, when such applications are covered it, he did not fail promptly to suggested by the laws which govern apply it to the solution of the practical the phenomena that have arisen in problem with which he had to grapple. their experimental researches. But

This problem was to enable the wecannot remember any other instance minor to walk, lamp in hand, through in which an object of research being an atmosphere of high explosive gas, proposed to an experimental philoso. without the possibility of producing pher, foreign to his habitual inquiries, explosion. It was, as though he were having no associations with those trains required to thrust a blazing torch of thought in which his mind has been through a mass of gunpowder without previously involved, he has prosecuted either extinguishing the Alambeau or the inquiry so as to arrive not only at igniting the powder; with this differ

the development of a natural law of the ence, however, that the gaseous at- highest order, the fruitful parent of mosphere to which the miner was often innumerable consequences of great geexposed was infinitely more explosive neral importance in physics, but has at than gunpowder.

the same time realised an invention of The instrument by which he accom- such immense utility as to form an plished this was as remarkable for its epoch in the history of art, and to besimplicity as for its perfect efficiency. come the means of saving countless A common lantern, containing a lamp numbers of human lives.

As wire-gauze drains Aame of its deposited over the object to be gilt danger in the safety-lamp, it drains may always be known with perfect exair of its poison by another felicitous actitude. application of a physical principle in An object may be silvered in some the case of the needle-grinder's mask. parts and gilt in others, by a very simIn that department of industry, the ple expedient. Let the parts intended health of the artisan was impaired, and to be gilt be coated with some nonthe duration of his life abridged, by conducting substance not affected by respiring continually, while at work, an the solution of silver, and let the object atmosphere impregnated with steel. be then immersed in the solution, and dust. A mask was invented composed put in connexion with the galvanic of a gauze formed of magnetised wire, battery as already described. The parts through which the artisan was to not coated will then be plated. Let breathe. The air, in passing from the the parts thus plated be now coated external atmosphere to the mouth and with a non-conducting substance not nostrils, left all the steel-dust which it affected by the solution of gold, the held in suspension on the wire of the coating previously applied being remask, from which, from time to time, moved, and let the object be immersed it was wiped off as it accumulated. in the solution of gold, and being con

Electricity has proved a fertile source nected with the battery, the parts not of benefits conferred on Art by Science. coated will be gilt. When a galvanic current is passed The result of the two operations through a Huid which holds in solution will be, that the object will be plated any substance which has the property on some parts and gilt on others. of being attracted by one of the poles In this manner, beautiful effects are of the battery, such substance will produced on vessels used for domestic desert the fluid, and collect upon any purposes, which are adorned with object, being a conductor, which may various designs expressed by such combe used to form the attracting-pole. binations of plating and gilding.

This fact has been already variously But of all the applications of electric applied in the arts, and in no case with agency to the uses of life, that which greater felicity and success than in is transcendently the most admirable in the process of gilding and silvering the its effects, and the most important in baser metals.

its consequences, is the electric teleThe process of electro-gilding or graph. No force of habit, however plating, which now forms so important long continued, no degree of famia department of industrial art, is easily liarity can efface the sense of wonder described.

which the effects of this most marvelLet us suppose that it be required to lous application of science excites. If gild an object formed of silver, copper, any sanguine and far-seeing votary of or any inferior metal. The object, science had ventured thirty years ago being first fabricated in the form it is to prognosticate the events which are destined to have, is submerged in a now daily and hourly witnessed in the fluid which holds gold in solution. It Central Electric Telegraph Office, is then put in connexion with the Lothbury, at the Ministry of the Inteattracting pole of the galvanic battery, rior in Paris, or in the Telegraphic while the solution of gold is put in con- Bureau at New York, he would have nexion with the other pole. The gals been pronounced insane by every sobervanic current thus passing through the

minded and calmly-judging person. solution, will decompose it, and the It is not many weeks since we, gold will attach itself to the metallic being in Paris, entered the Tele. object, which in a few seconds will be graphic Office, at the Ministry of the sensibly gilt.

Interior, in the Rue Grenelle St. Any quantity of gold which may be Germain. There we found ourselves desired can thus be deposited on the in a room about twenty feet square, surface of the object. This is accom- in the presence of some half-dozen plished merely by allowing it to remain persons seated at desks, employed in for a longer period of time in the solu- transmitting to, and receiving from tion. Thus the gilding may be regu- various distant points of France, deslated with the utmost precision, and patches. Being invited, we dictated the quantity of gold which has been a message, consisting of about forty words, addressed to one of the clerks iniles, and were joined to the extremity at the railway-station at Valenciennes, of the wire returning from Lille, thus a distance of an hundred and sixty- making one continued wire measuring eight miles from Paris. This mes- one thousand and eighty-two miles. sage was transmitted in two minutes

A message consisting of two hundred and an half. An interval of about five and eighty-two words was now transminutes elapsed, during which, as it mitted from one end of the wire. A afterwards appeared, the clerk to whom pen attached to the other end immethe message was addressed was sent diately began to write the message on for.

At the expiration of this inter- a sheet of paper, moved under it by val the telegraph began to express a simple mechanism, and the entire the answer, which, consisting of about message was written in full in the prethirty-five words, was delivered and sence of the Committee, each word written out by the agent at the desk, being spelled completely and without in my presence, in two minutes. Thus, abridgement, in fifty-two seconds, being forty words were sent an hundred and at the average rate of two words and sixty-eight miles, and thirty-five words four-tenths per second ! returned from the same distance, in By this instrument, therefore, it is the short space of four minutes and practicable to transmit intelligence to thirty seconds.

a distance of upwards of a thousand But surprising as this was, we soon miles, at the rate of nineteen thousand afterwards witnessed, in the same five hundred words per hour! room, a still more marvellous per- The instrument would, therefore, formance. A memoir on an improve- transmit to a distance of a thousand ment on the Electric Telegraph, by miles, in the space of an hour, the con. Mr. Alexander Bain, having been read tents of twenty-six pages of the book before the Institute, and submitted now in the hands of the reader !! to the Committee of the Legislative But it must not be imagined, because Assembly appointed to report on the we have here produced an example of project of law for opening the tele- the transmission of a despatch to a graphs to the use of the public, a distance of a thousand miles, that any series of experiments were ordered to augmentation of that distance could be made, with the purpose of testing cause any delay of practical importhis alleged improvement. The Com- tance. Assuming the common estimittee, among whom were M. Lever- mate of the velocity of electricity, the rier (celebrated for having discovered time which actually elapsed in the a planet before it was visible), M. transition of the despatch in this case Pouillet, professor of physics, and was the two hundredth part of a other distinguished persons desiring

a second. If, therefore, instead of to submit the invention to a more sending the despatch along a thousand severe test as to distance, than the ex. miles of wire, we had sent it along a isting telegraphs supplied the means wire completely surrounding the globe, of accomplishing, adopted the follow- the time of its transmission would still ing expedient:– Two telegraphic wires, be only the eighth part of a second.* extending from the Ministry of the Such a despatch would fly eight Interior to Lille, were united at the times round the earth between the two latter place, so as to form one continu. beats of a common clock, and would ous wire, extending from the Ministry be written in full at the place of its to Lille, and back from Lille to the destination more rapidly than it could Ministry, making a total distance of be repeated by word of mouth. When three hundred and thirty-six miles. such statements are made do we not This, however, not being deemed suf. feel disposed to exclaimficient for the purpose, several spiral " Aro such things here as we do speak about ? coils of wire, wrapped in silk, were

Or have we eaten of the insane root,

That makes the reason prisoner." obtained, measuring in their total length seven hundred and forty-six The wildest flights of the most exalted

We have here taken the usual estimate of the speed of an electric fluid ; recent experiments render it probable that it is somewhat less, and depends on the conductibility of the wire. Thus copper and iron giye different rates of transmission:

A very

imagination would not have dared, continuous current of electricity will even in fiction, to give utterance to be propagated along such bar or wire, these stubborn realities. Shakspeare from one end of the battery to the only ventured to make his fairy

other. Batteries of this kind are * Put a girdle round the earth

simple, cheap, steady, and continuous In forty minutes!"

in their effects ; their action being To have encircled it eight times in a maintained during a period of four second, would have seemed too mon- or five months, no other attention strous, even for Robin Goodfellow. being required than to renew the acid

The curious and intelligent reader solution from time to time, with which of these pages will scarcely be content, the sand is moistened. after the statement of facts so extra- Such an apparatus as that which ordinary, to remain lost in vacant as- we have here described, is to the elec. tonishment at the power of science, tric telegraph what a boiler is to a without seeking to be informed of the steam engine. It is the generator of manner in which the phenomena of the fluid by which the action of the nature have been thus wonderfully machine is produced and maintained. subdued to the uses of man.

We have next to explain how the brief exposition will be enough to electric fluid, generated in the appararender intelligible the manner in which tus just explained, can be transmitted these miracles of science are wrought. to a distance without being wasted or

The electric telegraph, whatever dissipated in any injurious degree en form it may assume, derives its effi- route. ciency from the three following con- If tubes or pipes could be conditions :

structed with sufficient facility and 1. A power to develope the electric cheapness, through which the subtle fluid continuously, and in the necessary fluid could flow, and which would quantity.

be capable of confining it during its 2. A power to convey to it any transit, this object would be attained. required distance without being in- As the galvanic battery is analogous to juriously dissipated.

the boiler, such tubes would be analo. 3. A power to cause it, after ar. gous in their form and functions to riving at such distant point, to make the steam-pipe of a steam engine. written or printed characters, or some The construction of such means of sensible signs, serving the purpose of transmission has been accomplished by such characters.

means of two well-known properties The apparatus used for producing of the electric fluid, in virtue of which the electric fluid consists of a series of it is capable of passing freely over a plates of zinc and copper, united in certain class of bodies called conduc. pairs, and placed in a porcelain, or tors, while its movement is arrested by wooden trough. The zinc plates are another class called non-conductors, or previously rubbed with mercury, which, insulators. combining with the superficial part of The most conspicuous examples of the zinc, forms a coating of amalgam, the former class are the metals ; the which renders the development of the most remarkable of the latter being electricity more regular and uniform. resins, wax, glass, porcelain, silk, cotThe cells between the successive pairs ton, &c., &c. of plates are filled with dry and per- Now, if a rod or wire of metal be fectly clean sand, which is moistened coated with wax, resin, silk, cotton, or with a solution consisting of eleven other insulator, the electric fluid will parts of water to one of strong sul- pass freely along the metal, in virtue phuric acid."

of its character of a conductor ; and A series of troughs, thus arranged, its escape from the metal to any lateral are called a galvanic battery; and if object will be prevented by the coatthey be united by metallic connexions- ing, in virtue of its character of an the series of plates following the same insulator. order, and their extremities being con

The insulator in such cases is, so nected by a metallic bar or wire-a far as relates to the electricity, a real

Other combinations are occasionally used, but the principle is the same.

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