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Your committee during the consideration of this subject invited to its meetings and sought the advice and assistance of a number of the most prominent illuminating engineers and arc lamp experts, and in that connection hereby expresses its appreciation for services rendered by Dr. Clayton H. Sharpe, Mr. Caryl D. Haskins, Mr. Frank Conrad, Mr. Carl Hering, Mr. Louis B. Marks and L. D. Howard Gilmour, and especially to Mr. W. D'A. Ryan for the quantity of data furnished to the committee for its use and the large amount of labor performed in the collection of additional data required in the preparation of the schedules.
(DUDLEY FARRAND, Chairman,
A. E. KENNELLY,
LOUIS A. FERGUSON,
CHAIRMAN KENNELLY: Gentlemen, you have had presented to you a report that has received very close attention from your officers. Vice-President Farrand has, to my personal knowledge, given a great deal of care and thought to the preparation of this report. It covers a matter of great importance to this association, as you know, not only on account of the recent developments at Colorado Springs, but also on account of the facts set forth in the papers of Messrs. Elliott and Floy, to which you have just listened. I will call on Dr. Steinmetz to open the discussion.
DISCUSSION DR. CHARLES P. STEINMETZ (Schenectady, N. Y.): Mr. President and Gentlemen: For nearly twenty years the carbon-filament incandescent lamp and the carbon-arc lamp held undisputed sway in the electric-lighting industry, and while a gradual slow progress was made, nó radical commercial advance occurred except perhaps in the replacement of the open arc by the enclosed arc, and both, as regards efficiency, were probably rather negative advances; that is, efficiency was sacrificed for convenience, reliability and steadiness. In the last few years we have experienced an enormously rapid advance. In the incandescent lamp field we saw appear the Nernst lamp, the metallized carbon-filament, the tantalum lamp, the tungsten lamp, and so gradually the efficiency of the incandescent lamp rose far beyond that of the arc lamp of old. In the field of arc lighting improvements have also taken place. In Europe the flame-carbon lamp was developed by impregnating the carbons with certain chemicals; the amount of light for a given aniount of power was increased many-fold, so that efficiencies unheard of before have been realized. The only unfortunate feature in connection therewith is that the flame-carbon lamp necessarily is an open or short-burning arc lamp, and the open arc had already practically disappeared from the American market.
For this reason, when the flame-carbon arc lamp was first spoken of in this country, I concluded that there would be practically no hope, in spite of its efficiency, to reintroduce it for general service here under American conditions, since it is a short-burning arc. It appeared to me that the first condition required in this country would be a long-burning, steady and white arc. This resulted in pushing the investigation of other carriers of the arc flame, and led the commercial development of the titanium-magnetite arc lamp as a luminous high-efficiency arc with long life, which now is well known.
The meeting here is especially gratifying to me because in the exhibition of magnetite arc lamps of other manufacturers, which you see at night in front of the hotel, full corroboration and recognition is found of my conclusion, from a source that I must recognize as being unbiased, that the field in America is for the long-burning flame-carbon lamp, and therefore in street illumination, where we must get high efficiency, carbon in the arc lamp must go. So I am gratified to see at this meeting that the magnetite arc lamp, for which I always had a kindly feeling, is now no more a special apparatus, manufactured by one company, but is recognized as one of the illuminants doing the world's lighting.
This, however, necessitates a readjustment of all our ideas, and especially of all our contracts, because these much higher efficiencies of illumination result in a higher cost to the station for power Four hundred and fifty watts spent by the station in a number of tungsten lamps of smaller candie-power, or a number of magnetite arc lamps, necessarily costs more than expending the same power in a single carbon-arc lamp. If we desire to give the public the benefit of these improvements in efficiency we must therefore arrange in our contracts to sell light, not power; otherwise we discriminate against the highefficiency illuminant. This was the purpose of the revised contract form for street illuminants, as your committee has drafted it. Probably further improvement may be made in future years, with increasing experience, but we had the experience of all the experts we could think of, and did the best we could under the rather difficult conditions,
When we deal with different sources of light there are three questions of importance: The first is the efficiency, the second is the size of the unit, and the third its color. What we desire is the highest possible efficiency. By their efficiency we can arrange the lamps in certain groups. With efficiencies of a fraction of a watt per candle-power, we have the flame-carbon lamp, the magnetite lamp and the mercury lamp. Next stands, in a group by itself, the tungsten-filament incandescent lamp. Then comes, with a gradually decreasing scale of efficiency, the old carbon-arc lamp, the tantalum lamp, the Gem filament lamp, the Moore tube, the Nernst lamp, and the old carbon incandescent lamp.
We have, however, also to consider the size of units. High efficiency is not the only thing. We get in the flame-carbon arc lamp an efficiency of a quarter of a watt per candle-power, but we get that only with a unit of thousands of candle-power, which
a would not be suitable for many uses where we need 16 candlepower, or 50 candle-power. So the size of the unit is of primary importance also. Arc lights are inherently at their best efficiency in units of many hundreds or thousands of candle-power; that is, they are large units. The incandescent lamps are smaller units of light. There is one curious feature--the higher-efficiency incandescent lamp is of larger size, almost in proportion to the higher efficiency, so that the power consumed per lamp remains about the same.
The old 16-cp incandescent lamp consumed 50 watts; the metalized-filament lamp still uses 50 watts but gives 20 candle-power. The smallest tantalum lamp gives about 25 candle-power, and the tungsten lamp 40 candle-power, still consuming 50 watts. So an increase of light given for the same power seems to give the commercial economy maximum of these illuminants.
The last point for consideration is the color, and here we find white in the magnetite lamp and nearly white in the tungsten filament, a yellowish white in the tantalum, a still more yellowish white in the Nernst lamp and the metallized-filament lamp, and ultimately yellow in the old incandescent lamp and the flamecarbon arc. You get the reddish white in the carbon arc and the Moore tube, and the bluish green in the mercury lamp. Vo one has yet produced a high-efficiency illuminant of blue color.
There is, however, one more feature to which I desire to draw your attention. There is a danger that we get into a rather awkward chaos of names if we do not look out. We have in the high-efficiency arc lamps two different types; one is the flame-carbon lamp—that is, a carbon arc made luminous and efficient by impregnating the carbon-and the other is represented by the magnetite lamp, a lamp in which the carbon is replaced by a different carrier of the arc flame. Thus far, only magnetite has been found suitable for this purpose. My recommendation would be to reserve the name of "flame-carbon arc," or, in short, "flame. arc,” for the impregnated carbon, characterized by the short life and high efficiency, and to adopt the name luminous arc or magnetite arc for those arcs in which the carrier of the current is a metallic oxide, more particularly magnetite, which gives a luminous flame. In the carbon lamp the flame comes from the foreign material introduced into the carbon, while in the magnetite lamp the vapor conductor itself is luminous, just as the Bunsen lamp is made luminous by heating a Welsbach mantle in it, or depositing carbon in it, while, for instance, burning zinc gives a flame that is luminous by itself. I would recommend to introduce this distinction between the magnetite arc as shown here and the flame arc; the one having a metallic oxide as a carrier, and the other having carbon as carrier of the arc flame, while the light-giving material in the latter is a calcium compound, giving a yellow glow, and in the former is titanium oxide, which gives it a white light.
a Mr. Louis A. FERGUSON (Chicago, Ill.): I think, after the splendid explanation given by Dr. Steinmetz on this subject of illumination, there is nothing I could say at this time.
MR. V. R. LANSINGH (New York city): I am sorry that I did not have an opportunity to read this paper over before it was read in this meeting, so as to be able to discuss it intelligently.
As it is, I have very little to say, as I believe the committee has gone very carefully into all phases of the subject. There is one thing, however, that seems to me not to have been taken into consideration. The vertical distribution of light has been carefully specified, but no attention has been given to the horizontal distribution. This is all right in cases where we wish light in all directions, such, for example, as the lighting of a square with lamps placed in the centre, but in street lighting we are primarily interested in throwing the light up and down the street, and not against the houses or into a vacant lot, if such there be opposite the lamp. This is especially true in sparsely settled districts where little or no reflection is obtained from such lighting. It seems to me, therefore, that the specifications should take into account not only the redistribution of vertical light, but also the horizontal distribution. It is, no doubt, possible to build reflectors or globes that would throw practically double the amount of light up and down the street as would be given without such globes and reflectors. For example, if we placed two small searchlights back to back, the street would be lighted in accordance with specifications, and yet, as a whole, be very poorly lighted. It might therefore be possible to do the lighting called for by the specifications with practically half the lighting that is really necessary in order to give good illumination. It seems to me, therefore, that in specifying proper units for street lighting we should take into account not only the redistribution of the vertical, but also the horizontal light, and I believe this is something that we are coming to, although but little work has been done along these lines up to the present time.
MR. W. D'A. RYAN (Lynn, Mass.): I had the pleasure of being present at some of the meetings of the committee on specifications for street lighting, and have endeavored to assist in drawing up a schedule of values to cover the specifications as outlined.
Several years' work has been reviewed and check tests have been made during the past two months, but up to the present it has not been possible to compile figures sufficiently stable to standardize on the foot-candle basis, owing to the many difficulties involved in making measurements. For example, the foot-candle illumination, estimated from candle-power curves using a distance of, say, 250 feet from the lamp, may not check up with the illu