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fire to the oil. That is the only instance of the kind that has come to my attention.

MR. LAYMAN: There was recently reported in the Engineering News, which is generally very reliable in the news that it prints, the fact that a transformer in process of construction by the company I represent had exploded and set fire to the oil and also to the factory.

The fact is that an entirely different situation existed. The transformer had been given a thorough test for load, and was being given a final insulation test. In making this test we followed our usual practice of gradually increasing the primary voltage above the normal. We were doing this as a final test, and there developed in the apparatus a defect in insulation and a strong arc resulted underneath the oil. The test was repeated a number of times, to locate the point of breakdown, while the oil was in the transformer. Then the oil was drawn off, and we began with a low pressure, endeavoring to produce the same jump without the oil, so that we could see its location. Finally, at a given pressure, a blaze resulted, and we located the point. The interesting fact was that we produced the arc a number of times under the oil without trouble, but had not been able to locate its position until after the oil had been drawn off.

THE PRESIDENT: There are no papers for the afternoon session, but a number of committee reports are to be presented. Before adjourning this session, I would urge you to be present this afternoon promptly at half-past two as there is a great deal of work to get through and we want to finish at a seasonable hour, in order that those wishing to catch the afternoon trains may do so.

Adjourned.

SIXTH SESSION

President Insull called the meeting to order at 2.55 p. m.

THE PRESIDENT: Has the committee on standard candle power of incandescent lamps any report to make?

MR. AYER: Mr. President, the committee, composed of Dr. Bell, Mr. Ferguson and myself, have had this matter in hand, but being so widely separated as we are, two members of the committee living in Boston and the other in Chicago, it is difficult for the members to get together. We have done some correspondence, and it has been necessary to carry on some experimental work. This has been done at the Boston Institute of Technology. Professor Puffer, of the engineering department, undertook to make a lot of determinations to enable us to get a basis for a set of specifications. We could not get the report of those investigations in time, but since my arrival here I have received a communication from Dr. Louis Bell that will give you a good idea of the work of the committee. I will present it as the report of the

committee.

REPORT OF THE COMMITTEE ON STANDARD CANDLE POWER OF INCANDESCENT LAMPS

Gentlemen:

Your committee has been able to have tested in the most careful manner, through the courtesy of Prof. W. L. Puffer, of Boston, sixteen-candle-power

incandescent lamps from eleven eleven different makers. The lamps were obtained directly from the makers or their authorized agents, and were known to be for

test.

These lamps were all all sold for sixteen candle power, 110 volts, no watts specified, watts specified, and may be fairly assumed to represent the product that would be shipped to consumers who did not desire the lamps for test; although one batch of lamps came marked to show the point to be

with the bases

turned toward the photometer screen.

Five

The

On test, these lamps-thirty-three in all-averaged 14.1 mean horizontal candle power and about 11.7 mean spherical candle power. Only one batch of three averaged over sixteen horizontal candle power. One batch fell below eleven horizontal candle power and two below twelve horizontal candle power. makers fell below 14.5 horizontal candle power. highest average of any batch was 16.99; the lowest, 10.82. The average consumption of energy was almost exactly four watts; the lowest, 3.78 watts per candle, and two batches ran over five watts. should be noted that the voltage was determined by a Weston voltmeter freshly compared with Clark cells, and each lamp was run at its marked voltage (110 volts).

It

A separate series of tests showed that these lamps on the average gave their mean spherical candle power when measured under rotation, with their axes tilted forty-four degrees twenty-four minutes. from the vertical toward the photometer, thus confirming closely your committee's estimate of forty-five degrees as a proper angle. The individual variations, however, were considerable, averaging several degrees. A series of tests on proper speed of rotation

showed that the best results were obtained with a speed of 200 to 250 revolutions per minute, and that the lamps would readily stand this speed.

Many of the lamps showed had spherical distribution, which seems to be quite needless, since it is merely a matter of properly proportioning the form of the filament.

Of an equal number of batches of thirty-twocandle-power lamps, only one batch averaged thirtytwo horizontal candle power, the majority falling to twenty-six and twenty-eight candle power. The thirtytwo-candle-power lamps averaged slightly greater efficiency, but were otherwise much like the sixteencandle-power size.

From this investigation, the fact stands out that the incandescent lamp sold for sixteen candle power is, on the whole, a lamp giving considerably less than its rated candle power, even when new. Some of these lamps would probably show a temporary increase of of candle power after, say, fifty hours' burning; but the committee has not extended the research in this direction as yet, and adheres to the opinion that initial candle power is the only practicable commercial test, and consequently any increase is simply regarded as a device for keeping the lamp a little longer from its inevitable decay.

From these and other data kindly furnished by manufacturers and obtained from various other reliable sources, your committee is convinced that the need of a uniform rating is even greater than it concluded in the preliminary report of last year, and that a rating test, in order to be effective, must involve measurement of candle power of lamps in more than one direction. Neither mean horizontal or mean spherical candle power, nor candle power in any one direction,

will define a lamp well enough to insure adherence to the rating.

Your committee therefore recommends that incandescent lamps be required to conform both to a standard mean horizontal candle power and to a mean candle power when revolved with the axes tipped fortyfive degrees, this representing the spherical distribution.

It recommends that the limits for the mean horizontal candle power be fifteen and 17.5 candle-power. Unless the minimum be as high as fifteen, there will certainly be found a tendency to produce lamps near the lower limit. The forty-five-degree candle power should be at least eighty-five per cent of this minimum. This is not an excessive requirement, and will tend to prevent working near the lower limit of horizontal candle power unless with a lamp very good in other respects.

Your committee has blocked out a standard form of photometer, a type of which it proposes to build, test and put at the disposal of the association with directions for proper use.

It suggests that testing be by sample, a lot of ten lamps being taken from each barrel. Of these, no lamp when run at its marked voltage shall show less then fifteen or more than 17.5 candle power (mean horizontal) when rotated at 200 to 250 revolutions per minute. And no lamp shall give, when thus rotated at forty-five degrees inclination, less than eighty-five per cent of the above minimum.

Your committee will make arrangements for standard lamps as indicated in the preliminary report, to go with the standard photometer.

Respectfully submitted,

LOUIS BELL, Chairman,
JAMES I. AYER,

LOUIS A. FERGUSON.

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