considered as essentially unsuitable for this purpose. The researches were mostly made along the lines of alkaline batteries. Finally the aim was the design of an oxygen lift cell, with potassium or sodium hydroxide as electrolyte and electrodes simply undergoing oxidation and reduction and insoluble in the electrolyte in all states of oxidation. Several inventors have worked along this line, among them Jungner. But commercial success was first attained by Thomas A. Edison with his nickel iron battery, which, it seems, will have a field of its own, especially for automobile work.

A QUARTER CENTURY OF ELECTRIC LIGHTING.

BY LOUIS BELL.

[Louis Bell, consulting electric engineer; born Chester, N. H., Dec. 5, 1864; resides in Boston, where, besides his active life in his profession, he has found time to write many scientific and technical essays chiefly for the Engineering Magazine, in which the article here published first appeared; also author of the following books among others: The Electric Railway, Electrical Power Distribution; Power Distribution for Electrical Railways; The Art of Illumination. The following article is republished from the Electrical World by special arrangement.]

Copyright 1904 by McGraw Publishing Company

The growth of a new art is a startling phenomenon. The familiar manufacturing enterprise of a nation may, under normal conditions, be expected to keep pace with the growth of the population in numbers and in wealth and save for commercial disaster now and then, or for artificial stimulus by governmental action, to move forward at a fairly regular rate. But the irruption of a new art like electric lighting is a very different matter. It grows in response to a law of demand that bears no definite relation to anything and while, of course, this growth is affected by local causes and by the conditions of general prosperity, it depends largely on intrinsic factors in the art itself, the effect of which cannot be predicted, but becomes visible in the fullness of time.

One may study the phenomenon of such growth as a pure matter of statistics, but while such an examination may, like other statistics correctly show effects, it fails utterly, as statistics usually do, in showing the causes which produce them. Cause and effect can be correlated, but only by studying the circumstances which are current with the figures. The relations between figures and facts are far too complicated to be self evident.

Starting, then, with the broad facts that about twenty six years ago incandescent lighting by central stations began, and that to-day the whole business occupies 3,700 stations, represents an investment of more than half a billion dollars, and draws a gross yearly income of nearly ninety million dollars, it is worth the while to attempt to trace the reasons

for so prodigious a growth and the factors which have gone to produce it.

In that quarter century the population of the country has increased about 80 per cent, and few large industries have exceeded this rate of growth; but electric lighting, starting from absolute nonexistence, has risen to an industry of first rank in the face of strong competition from other illuminants, and what is more, in the face of a cost which throughout its whole early history was undeniably higher than that of any other illuminant. It has made its way through the operation of favoring factors other than economy, ranking as a luxury rather than a necessity, and only within a few years being able to meet competition on a simple basis of cost. These facts are very unusual in the history of a great industry and deserve careful consideration. They are the more extraordinary when one considers that for some years electric lighting was not only upon the whole the most costly but the least reliable form of illumination, was fought viciously by the fire underwriters, suffered from ferocious internecine war among its exponents, and had been a very Gettysburg of patent litigation.

When late in 1879 the incandescent lamp appeared as a commercial possibility, the arc lamp had already been for some years in slowly increasing use both here and abroad, mostly for small private installations, for the quite sufficient reason that the largest arc dynamos would handle but a few lamps, not enough to cut any figure at all for anything but the smallest plants. Nevertheless it was perfectly evident that the arc had come to stay. It had the inestimable property of giving white light in the form of a very intense and powerful unit. Before the electric arc came into use, lights of similar power were practically nonexistant, and the arcs could therefore give a brilliancy of effect hitherto unknown. This fact of itself accounted for their rapid growth in popularity and when their accurate rendition of color values is taken into account, it is small wonder that they made a sensation. The Jablochkoff candle, practically the earliest commercial form of arc, was, in spite of its limitations, altogether remarkable in the quality of the illumination given, and, in

fact, would be difficult to surpass in this particular. It is interesting to note that it has continued in limited use even up to the present time.

The arc lamp therefore did the pioneering for the incandescent lamp. It educated the public to the appreciation of the importance of color values in illumination, drew once for all a line between weak illuminants and powerful ones, and caused all eyes to be turned to electricity as the coming source of illumination.

Then came the incandescent lamp in response to the demand for smaller electric lights. The subdivision of the electric light was the problem of the day, and very fortunately this problem was solved by the glow lamp instead of by arcs of small candle power, which could not then have been, and, in fact, never have been, satisfactory illuminants. The incandescent lamp nearly equalled the arc in rendering color values, and enormously surpasses it in convenience and steadiness.

It was far less economical than the arc and was not for some time on public circuits able to compete with gas, but made its way by reason of its better color, its steadiness and its freedom from vibration of the air, and from overheating. These good qualities carried it ahead in spite of all opposition. It is hard to realize to-day how much these gains meant in the way of exterior illumination, but they were fully realized at the time, and they unquestionably won the day for electric lighting. Looking over some ancient history recently the writer came across a printed letter reporting results from one of the early isolated plants, that in the Pemberton mills, installed in October, 1881. Although in this case two four-foot gas jets were replaced by each "A" lamp of 16 candle power, a great improvement was noted in the conditions of illuminations, especially in regard to color vision in work on colored fabrics, and in the purity of the atmosphere. Further, it was shown that the cost of the electric light, including interest and depreciation at 12 per cent, and lamp renewals at $1.00 apiece, was less than the cost of gas for the burners replaced by more than a half.

One smiles nowadays at the idea of replacing two fourfoot gas jets by one 16 candle power lamp, but the fact of doing so was a valuable lesson in illumination-proof that a steady light, good in color, can actually with positive advantage replace lights of greater gross intensity, but lacking these two things.

A good many people who ought to know better, but have not learned this lesson, still foster the idea that illumination intrinsically bad can be made good by merely increasing its quantity.

The incandescent light practically won its way through quality, for only under rare conditions could it at first show economy over gas at the prices generally current. Once introduced and appreciated it was rapidly pushed ahead. It was a thing to advertise in one's business and to brag about to one's neighbors, and its use thus spread with the added momentum due to fashion. With it came increased use of arc lamps, partly in competition, but still consistently backing up the public demand for bright light and more of it. Pretty bad some of those early arcs were too, but they did what gas had never done they really lighted large areas effectively by dint of sheer brilliancy. Between the arcs and incandescents there was awakened a demand for public electrical supply, though, by a strange streak of fate, the arc and the incandescent systems, beautifully fitted to supplement each other's work, fought like cat and dog, damning each other with an ingenuity of objurgation that would be worthy of a unique position in profane history. Apparently this mutual abuse simply served to make violent partisans and both systems flourished. Forward steps were rapid, and on one hand arc machines carrying a respectably large series of lamps soon came into use, and the carbons, at first horribly bad, were so improved in manufacture as greatly to better the steadiness of the light. On the other hand, incandescent lamps were greatly improved in manufacture so that their useful life was largely increased, the bamboo filament was fashioned into as good practically working form as its nature permitted, and the invaluable three-wire distribution was brought into wide In large cities incandescent lighting was giving good