that there shall be as little shadow as possible, and that each object in the room shall be as nearly as possible illumined all around, so that the reflection from them may help to illumine other objects which do not get the direct rays. For this reason I respectfully contend that the illumination of the space we inhabit is greater with the flat-flame burner than with the Edison light.

MR. CLARK-I think the proceedings of this year will be very rich in information concerning light—both theoretical and practical. I think we should be specially grateful to Mr. Humphreys for having settled this question of diffusion, as it is one which has vexed us a good deal. The papers are of such a character that it is hard to discuss them off-hand. We will enjoy them very much when reading them, but we cannot readily discuss them on short notice. They are too deep for us.

MR. LowE-I would like to ask President Morton a question. If you were to take two flames of equal intensity-for instance, a yellow flame of twenty-candle power and a white flame of twenty-candle power, and take a given area of each, say one square inch-what would be the difference, if any, in the illumination at equal distances?

PRESIDENT MORTON-If they were equal at one distance they would be equal at all other distances. That is to say, if they were tried, as in the experiment described by Mr. Humphreys. If we had a yellow flame here, and a white flame there, and so adjusted their relative strengths that they gave equal illumination upon a surface intermediate between the two, then if we moved them both equally away from the surface, the illumination would remain equal on that surface.

MR. LOWE-Notwithstanding the color of the light?

PRESIDENT MORTON-Notwithstanding the color.

MR. LOWE―Then you do not think that a sixteen-candle coal gas is better than a twenty-candle power water gas?

PRESIDENT MORTON-No; I should not think so, as a matter of mere illumination.

MR. BOARDMAN-In testing the candle power of different

flames, did you ever observe the relative size of those flames necessary to give the candle power?

PRESIDENT MORTON-Yes.

MR. BOARDMAN-Then I should like to ask whether the yellow flame requires a larger surface or a smaller one, or a surface of the same size, in order to give the same candle power by the photometer ?

PRESIDENT MORTON-The yellow flame undoubtedly requires a larger surface to give the same amount of light as compared with a white flame. In other words, a white flame, from the nature of things, has a more intense action. And that reminds me of a point which I think will interest you. A great many years ago Prof. John W. Draper, of this city (now dead), who was one of the most original of American scientists, went into this subject and investigated it thoroughly. He found that where a body was rendered luminous by heat, as, for instance, a platinum wire, this was the order in which the colors appeared: When it first became luminous the rays were entirely red; as it became more luminous, there were added, to those red rays, yellow rays; but the red rays were also increased. There came more red light than before with the yellow light added to it. Then, as the heat was increased still more, the red was increased, the yellow was increased, and there was added to them green rays. As the heat was still further increased there was added to the green, blue; and to the blue, violet; but, with each addition of the higher colors, the amount of the light of the lower colors was increased. In other words, we find that in order to get up to such a compound of colors as will give us the white light— that is, a compound which must have in it blue, and violet, as well as the others-we must have a great amplitude of motion or intensity of the lower ones as well as of the higher. In still other words, when we get the white light it is by having a very intense or very powerful vibratory action, or the amplitude of the longer waves must be great in order to bring the shorter waves out so as to produce white light.

THE PRESIDENT-I do not see that there is very much left for the adherents of coal gas, theoretically; but I think that some of

us are still unconverted. It seems to me to put the thing in this way, that, theoretically, if you will take five feet of thirty-candle gas, you ought to get from it as much light as you would from a larger burner, burning ten feet of fifteen-candle gas; or as you would get from the same amount of gas, or from two of these Edison burners. Now, as matter of fact, I believe that if you should compare the light upon a surface which was lighted by a large flame burning ten feet of coal gas, with that lighted by a flame which was burning five feet of thirty-candle gas, you would find the room would be better lighted by the ten-foot burner. It seems to me there would be more diffusion in the room; although theoretically, I do not know that I have any reason to give for it except the size of the flame.

PRESIDENT MORTON-I think you are correct, theoretically as well as practically, up to a certain limit. In order that a gas with half the intensity of illumination should produce the same total amount of light, there must be a double area by which the light is produced. That, of course, will diminish the sharpness of the shadows. When we are speaking of single lights it is manifestly true that if you have a light which is one square inch in area, and are getting from that a certain total amount of light and then get the same number of candles from two square inches of light, the intensity must be diminished proportionately; half the intensity involves double the area. With this double area you are getting a better diffusion; it will go more around the columns; it will better light up spaces that otherwise would be shaded; it will diminish sharpness of the shadows, etc. That is undoubtedly true. In practical illumination, however, we are dealing generally with a number of lights. It is very rarely that we attempt to light a room from an absolutely single source. Where we are dealing with a number of lights, and multiply the number of lights when you reduce the intensity, then we are gaining in both ways, because, of course, it is easier to light a space by putting two lights a quarter way from each end than by lighting with one light in the middle, for this law of decrease in proportion to the square of the distance makes it disadvantageous to light from a single source. In any case in which distribution by breaking up one light into several comes in, of

course there is great advantage in a number of sources of light as compared with a single one. But I do not think, aside from this, that there is a difference if a given area (say a square inch) is given, of twenty candle-power, and that light is falling on a plain surface, and another of two square inches, which is also giving off a twenty-candle light, which falls on that same surface. Then I cannot conceive that there can be a difference of illumination, except such as may be due to the different colors of the lights. One may illuminate with a pure white light; another may illuminate with a yellow or reddish light; and one or the other may be agreeable; and one or the other may light a surface, if it is a colored surface, very much better than the other. If a majority of the objects are of yellow color, a yellow light will illumine them much better than any other color. If those same objects were blue, then a yellow light would be feebler in its illumination. If we had a room of more chromatic color, all red or all yellow, we could then best light that room with a light of a corresponding color; but, if a room is decorated with all sorts of colors, then the whitest light that we can get the nearer in fact we can approach to daylight-the more distinctly all the colors will equally appear.

MR. EDGERTON-I understood that the starting point of this discussion was the assertion that sixteen-candle coal gas illumined as well as twenty-candle water gas. I desire to call your attention to a practical illustration—a case of illumination in London, England, where they have a twenty or twenty-one-candle cannel coal gas and a nominally sixteen-candle common gas; and yet, as a practical test, the cannel gas is sold at four shillings, whereas the common gas is sold at two shillings and three pence.

On motion of Mr. Clark, a vote of thanks was tendered to Messrs. Humphreys and Jones for their papers.

Mr. A. C. HUMPHREYS-I wish to say, before moving a vote of thanks to President Morton, and before the discussion on this subject is closed, that last night I made a practical experiment, not a scientific one, in my room, with two light-giving surfaces; two Welsbach mantles, one being perfectly white and the other being a very mellow yellow. So far as I could see they were of

the same size, made from the same materials, and practically the same. I have no doubt that, tested on the photometer, they would have been found of the same candle-power. The lighting effect in the room, as we speak of it, from the yellow flame appeared superior, as it was more pleasant to the eye; but when I asked some of those with me to read print at a certain distance from the light, they could read it from the white light the best.

I move the thanks of the Association to President Morton for his very interesting remarks upon this subject. I regard them as a practical lecture, covering some very important features, and I think that, if we deserve thanks for our papers, President Morton most certainly deserves our thanks for his address.

THE PRESIDENT-I understood that in voting the thanks of the Association, we included all three of the gentlemen whom we had the pleasure of hearing, but I am very happy to put a motion tendering a special vote of thanks to President Morton for his entertaining remarks.

The motion was passed.

Mr. C. H. Nettleton, of Birmingham, Conn., then read his paper on the

UTILILZATION OF RESIDUAL PRODUCTS.

Unfortunately the committee appointed by your Association to appoint certain members to prepare papers for this meeting, selected the speaker as one of the victims. It was unfortunate in a double sense for the Association, as a better selection could easily have been made and a far better paper been listened to than the one you will now hear; and unfortunate for the speaker, as the press of business has been so great with him this fall that sufficient time could not be spared to give the subject named by the Committee the thought necessary, or the few thoughts he had, the proper expression. I dislike to offer the Association an apology after promising to write, but it has been impossible to prepare a paper worthy of the subject or the occasion.

The notice which I received from our Secretary stated that I had been appointed to prepare a paper on the "Utilization of of Residual Products" to cover the probable return, not only in