Rough Ways Made Smooth: A series of familiar essays on scientific subjects

by Richard A. Proctor

(except that the two v's are not in the same plane, but in planes at right angles to each other). The spark crosses the space between the points of the v's, and arrangements are made for keeping the two points at the right distance from each other, and also for keeping the ends of the two pencils which form each point in their proper position. If the current is from any cause interrupted, an automatic arrangement is adopted to allow the current to pass to the other lamps in the same circuit. There are six lamps in circuit at the 'Times' office; and M. Rapieff has exhibited as many as ten. The advantages claimed for this light are the following:—'First, its production by any description of dynamo-electric machine with either alternating or continuous currents; secondly, great diversibility and complete independence of the several lights, and long duration without change of carbons; and lastly, the extreme facility with which any ordinary workman or servant can renew the carbons when necessary, without extinguishing the lights.' The last-named advantage results, it need hardly perhaps be said, from the use of two carbons to form each point. One can be removed, the other remaining to keep the voltaic arc intact until a new carbon has been substituted for its fellow; then it in turn can be replaced by a new carbon, the new carbon already inserted keeping the voltaic arc intact.

The six lamps at the 'Times' office thoroughly illuminate the room, and give light for working the eight Walter presses used in printing the paper. The light has been thus used since the middle of last October, and it is said that other rooms in the building are shortly to be illuminated in the same manner. 'Each lamp is enclosed in an opal globe of about four inches in diameter, and so little heat is given off, that the hand can be placed on the globe without inconvenience, even after the light has been burning for some time.'

In the Wallace lamp there are two horizontal plates of carbon, about nine inches in diameter, instead of mere carbon points. When the current is passing, these carbon plates are separated by a suitable small distance which remains unchanged. The electric arc, being started at the point along the edge of the carbons where there is least resistance to the passage of the current, gradually passes along the edge of the carbons as combustion goes on, changing the position of the place of nearest approach and consequently of least resistance. The light will thus burn for many hours (even for a hundred with large carbon plates), and any number of lights up to ten can be worked from the machine. The objection to the Wallace lamp is, that the light does not remain at one point, but travels along the whole extent of the carbons. It will not be easy to design a glass shade which will be suitable for a light thus changing in position.

The Werdermann regulator is on an entirely new plan; but it has not yet been submitted to the test of practical working outside the laboratory. The positive carbon, which is lowest, ends in a sharp point, which strangely enough retains its figure, while the carbon burns away at the rate of about two inches per hour. The negative carbon is a block having its under side, against which the positive carbon presses, slightly convex. The positive carbon is pressed steadily against the negative by the action of a weight. The increased resistance to the passage of the current, at the sharp point of the positive carbon, generates sufficient heat to produce a powerful light. The light resembles a steadily radiant star, but 'with all its softness and purity of tint, it is so intense, that adjacent gas-flames are thrown on the wall as transparent shadows.' The light will last for fifteen hours without attention, the positive carbon rod being used in lengths of three feet. The carbon block hardly undergoes any change. When the lamp has been burning a long time, a slight depression can be seen at the place where the positive carbon touches it, but by shifting the carbon in its holder this is easily remedied. Mr. Werdermann lately exhibited a row of ten small lamps burning side by side at the same time. 'The two wires from the machine,' says Mr. Hepworth, were carried one on either side of this row of lamps, branch wires being led from them for the service of each lamp. Mr. Werdermann says that his perfected lamps will be furnished with keys, by which the current can be turned on or off, as in the case of gas. We may say in fact, that in the nature of its connections and various arrangements, it ("the Werdermann lamp") most nearly comes up in convenience to the use of gas.'

We do not yet know certainly what arrangement Mr. Edison employs to obtain the light of which so much has been heard. It is asserted that his light is obtained from the incandescence of an alloy of iridium and platinum, which will bear without fusion a heat[26] of 5,000 degrees Fahrenheit. It would be unsafe, however, to assume that this account is trustworthy, or to infer (as we might in the case of almost any other inventor), that such being the nature of his plan, it could lead to no result of practical value. As has been well remarked by a contemporary writer, whatever Edison's invention may be, 'it is certain to be something to command respect, even if it does not quite come up to the glowing accounts which have reached us in advance.'

The following passage from one of these accounts, which appeared in the 'New York Herald,' will be read with interest, and may be accepted as trustworthy so far as it goes. 'The writer last night saw the invention in operation in Mr. Edison's laboratory. The inventor was deep in experimental researches. What he called the apparatus consisted of a small metal stand placed on the table. Surrounding the light was a small glass globe. Near by was a gas jet burning low. The Professor looked up from his work, to greet the reporter, and in reply to a request to view the invention, waved his hand towards the light, with the exclamation, "There she is!" The illumination was such as would come from a brilliant gas jet surrounded with ground glass, only that the light was clearer and more brilliant. "Now I extinguish it and light the gas, and you can see the difference," said Mr. Edison, and he touched the spring. Instantly all was darkness. Then he turned on the gas. The difference was quite perceptible. The light from the gas appeared in comparison tinted with yellow. In a moment, however, the eye had become accustomed to it, and the yellowish tint disappeared. Then the Professor turned on the electric light, giving the writer the opportunity of seeing both, side by side. The electric light seemed much softer; a continuous view of it for three minutes did not pain the eye; whereas looking at the gas for the same length of time caused some little pain and confusion of sight. One of the noticeable features of the light, when fully turned on, was that all the colours could be distinguished as readily as by sunlight. "When do you expect to have the invention completed, Mr. Edison?" asked the reporter. "The substance of it is all right now," he answered, putting the apparatus away and turning on the gas. "But there are the usual little details that must be attended to before it goes to the people. For instance, we have got to devise some arrangement for registering a sort of meter, and again, there are several different forms that we are experimenting on now, in order to select the best." "Are the lights to be all of the same degree of brilliancy?" asked the reporter. "All the same!" "Have you come across any serious difficulties in it as yet?" "Well, no," replied the inventor, "and that's what worries me, for in the telephone I found about a thousand;[27] and so in the quadruplex. I worked on both over two years before I overcame them."'

Other methods, as the Sawyer-Man system, and the Brush system, need not at present detain us, as little is certainly known respecting them. In the former it is said that the light is obtained from an incandescent carbon pencil, within a space containing nitrogen and no oxygen, so that there is no combustion. In the latter the carbon points are placed as in the ordinary electric lamp, but are so suspended in the clasp of a regulator, that they burn 14 inches of carbon without adjustment, the carbons lasting eight hours, and producing a flood of intense white light, estimated as equivalent to 3,000 candles.

I have little space to consider the cost of electric lighting, even if the question were one which could be suitably dealt with in these pages. Opinions are very much divided as to the relative cost of lighting by gas and by electricity; but the balance of opinion seem to be in favour of the belief that in America and France certainly, and probably in this country, where gas is cheap, electric lighting will on the whole be as cheap as lighting by gas. It should be noticed, in making a comparison between this country and others in which coal is dearer, that the cheapness of coal here, though favourable in the main to gas illumination, is also favourable, though in less degree (relatively) to electric lighting. Machines for generating electricity can be worked more cheaply here than in America. Nay, it has even been found advantageous in some cases to use a gas engine to generate electricity. Thus Mr. Van der Weyde used an Otto gas engine driven at the cost of 6d. an hour for gas, to produce the light which he exhibited publicly on the night of November 9. So that the cheapness of gas may make the electric light cheaper. Then it is to be remembered that important though the question of cost is, it is far from being all-important. The advantages of electric lighting for many purposes, as in public libraries, in cases where many persons work together under conditions rendering the vitiation of the air by gas lighting exceedingly mischievous, and in cases where the recognition of delicate differences of tint or texture is essential, must far more than compensate for some slight difference in cost. The possibility (shown by actual experience to be real) of employing natural sources of power to drive machines for generating electricity, is another interesting element of the subject, but could not be properly dealt with save in greater space than this here available.

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