[D8907ACO], Letter from Public Opinion to Thomas Alva Edison, November 7th, 1889
[AC/DC; unsigned editorial or letter in Public Opinion] Dangers of Electric Lighting.- The currents used for electric lighting at the present time may generally be divided into four classes: First, the low-tension continuous current, with a pressure not exceeding 200 volts, used for incandescent lighting: second, the high tension continuous current, with a pressure of 2,000 volts and over; third, the high-tension continuous current, with a pressure of 2,000 volts and over; third, the high-tension semi-continuous current, with a pressure of 2,000 volts and over; fourth, the alternating current, with a pressure from 1,000 to 3,000 volts and over. The first is harmless, and can be passed through the human body without producing uncomfortable sensations. The second is dangerous to life. Momentary contact with a conductor of the third results in paralysis or death, as has frequently occurred; and the passage of the fourth, or alternating, current through any living body means instantaneous death. These are simple facts which can not be disproved. There is a record of nearly one hundred deaths, which furnishes an unanswerable argument in support of these statements. Discussion and controversy may serve the questionable purpose of delaying popular faith in them, but they can not change them; and the sooner they are accepted and acted upon the less liability will there be of a recurrence of the late horror (In New York city). Many suggestions have been made as to the best way in which to remedy the existing evil, and the popular cry seems to be, “Put the wires underground.” But, instead of diminishing, this will increase the danger to life and property. There is no known insulation which will confine these high tension currents for more than a limited period, and when they are placed beneath the ground, with the present system of conduits, the result will be a series of earth contacts, the fusion of wires, and the formation of powerful electric areas, which will extend to other metallic conductors in the same conduit, and a w hole mass of wires made to receive this dangerous current and convey it into houses, offices stores, etc. It is thus evident that the dangers of such circuits are not confined to the wires which convey the high tension currents, but other wires conducting harmless currents are liable to be rendered as deadly in effect as the former. It is evident, also, that a single wire carrying a current at high pressure would be a constant menace to the safety of all other wires in the same conduit. Even though these dangerous wires be placed in separate tubes in the same conduit with other tubes, the risk is not diminished. Several instances are on record, and one I have particularly in mind, showing the possibility of serious accident through the crossing of wires. Near the corner of William and Wall streets, New York, the underground conductors of the Edison illuminating Company became crossed, and the current which was passing through them at a pressure of only 110 volts melted not only the wires, but several feel of Iron tubing in which they were increased, and reduced the paving-stones within a radius of three or four feet to a molten mass. This system is so arranged that consumers are not affected by such accidents as this. They may and do mean expense to the company, but the public are entirely free from any possibility of danger. The crossing of wires in this way means the concentration of several hundred horse-power of energy in a small space. What would have been the effect of such a cross as I have described had the pressure been 2,000 instead of 110 volts? And what also might be the effect where it to occur in a conduit in close proximity to hundreds of telephone wires and those of other electric lighting systems? The risk, too, is greatly increased by the fact that consumers who are supplied with currents from a low tension system are accustomed to handle their electrical applicanced freely, knowing them to be harmless. If these are to be rendered at any moment dangerous to life, the result will be appalling. So far, the deaths which have occurred from this source have been chiefly confined to employee of electric-lighting and telegraph companies- men whose duties have required them to work in close proximity to the conductors of these death-dealing currents. It is true that a number of accidents, many of them attended with fatal results, have occurred to pedestrians on the streets of New York and other cities through the medium of fallen wires; but the risk incurred by the general public with the present system is really less than it would be if these dangerous conductors were placed in closer proximity to the ground. As the earth is approached the danger is multiplied. The connection and crossing of two wires by a line of moisture or liquid contact are just as effective as the contact of one wire with another when overhead. The insulation of of a wire carrying a high-tension current in the most perfect manner known may insure temporary safety; but time is bound to develop defects as the result of the action of the current upon the insulating material, of a change in the molecular structure of the material inteself, anf for other reasons. The pulsations or vibrations in an electric conductor cause corresponding vibrations in the insulation. So powerful is this effect that insulation gives off a sound corresponding to the oscillation of the current. So long as the insulation retains its original elasticity, the current is confined but the influence of the air or of gas and other agents, tends to change the elasticity, and the billions of vibrations to which it has been subjected finally render it very susceptible of being pierced by a spark of static electricity. Thus an avenue for the ingress of moisture is formed, not only in one spot, but in many, through which the current may be communicated to any conductor of electricity near enough to make physical contact, or a circuit may be completed between the two by a line of moisture or the formation of an electric are, with its subsequent destructive action. I have no intention, and I am sure none will accuse me, of being an alarmist. When the possibilities of the future are viewed in the light of recent-developments, it must be apparent to everyone that the time has come when those in authority should adopt proper and adequate measures for the protection of life and property, and my familiarity with the subject enables me to see very clearly the only true remedy which can be applied-namely, the regulation of electrical pressures. Once these pressures are reduced to a point which is the harmless, the public may retire in security and leave electricians to discuss the merits or demerits of various methods of insulating, the defects of which will only concern those interested in the commerce of electricity. There is no plea which will justify the use of high-tension and alternating currents, either in a scientific or a commercial sense. They are employed solely to reduce investment in copper wire and real estate. For instance, in arclighting it is customary to put forty lamps on each circuit; each lamp requires a pressure of 50 volts; therefore the total pressure on the circuit is a 2,000 volts. Now, if, instead of using only one wire for all these lamps, four circuits of then lamps each were to be established, the pressure on each wire would be 500 volts. The weight of copper necessary for these four circuits of ten lamps each would be two and a half times greater than for one circuit of forty lamps ### Public Opinion ## Is an attractive weekly publication giving a broad, well classified and perfectly unbiased Digest of the current thought of the nation as expressed by its leading periodicals and writers. ## It covers thoroughly the fields of politics, science, finance, literature, religion, sociology, etc., and brings to the reader in convenient form for quick perusal what it would be impossible to procure otherwise, without a vast expenditure of time and money. ## The aim of public opinion is not to create but to reflect public opinion. Its corps of editors read carefully all the principal daily papers of the entire nation, and also all the magazines and scientific, literary, financial, and religious weeklies. 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[D8907ACO], Letter from Public Opinion to Thomas Alva Edison, November 7th, 1889
Thomas A. Edison Papers, School of Arts and Sciences, Rutgers University
November 7, 1889