SCIENTIFIC AMERICAN SUPPLEMENT NO. 458 NEW YORK, OCTOBER 11, 1884

BAYLE'S LAMP CHIMNEY.
The different types of lamps used in domestic lighting present several imperfections, and dailyexperience shows too often how difficult it is, even with the most careful and best studied models,
to have a perfect combustion of the usual liquids—oil, kerosene, etc.

Mr. P. Bayle has endeavored to remedy this state of things by experiments upon the chimney,inasmuch as he could not think of modifying the arrangements of the lamps of commerce "without
injury to man" interests, and encountering material difficulties.
The chimney is not only an apparatus designed to carry off the smoke and gases due to combustion,for its principal role is to break the equilibrium of the atmospheric air, which is the great reservoirof oxygen, and to suck into the flame, through the difference of densities, this indispensable agent
to combustion. The lamps which we now use are provided with cylindrical chimneys either with orwithout a shoulder at the base. The shouldered chimney would be sufficient to suck in the quantityof air necessary for a good combustion if we could at will increase its dimensions in the direction ofthe diameter or height. But, on account of the fragile nature of the material of which it consists, asalso because of the arrangement of the lighting apparatus, we are forced lo give the chimney limited
dimensions. The result is an insufficient draught, and consequently an imperfect combustion. It
became a question, then, of finding a chimney which, with small dimensions, should have greatsuctional power. Mr. Bayle has taken advantage of the properties of convergent-divergent ajutages,
and of the discovery of Mr. Romilly that a current of gas directed into the axis and toward the smallbase of a truncated cone, at a definite distance therefrom, has the property of drawing along with it aquantity of air nearly double that which this same current could carry along if it were directed
toward a cylinder. In getting up his new chimney, Mr. Bayle has utilized these principles as follows:
Round-burner lamps have, as well known, two currents of air—an internal current which traverses
the small tube that carries the wick, and an external one which passes under the chimney-holder
externally to the wick. In giving the upper part of the chimney, properly so called, the form of atruncated cone whose smaller base is turned toward the internal current of air, that is to say, indirecting this current toward the contracted part of the upper cone, at the point where the depression
is greatest, a strong suction is brought about, which has the effect of carrying along the air between
the wick and glass, and giving it its own velocity. The draught of the two currents having beeneffected through the conical form of the upper part of the chimney, it remained to regulate theentrance of the external current into the flame. If this current should enter the latter at too sharp anangle, it would carry it toward the mouth of the chimney before the chemical combustion of thecarbon and oxygen was finished; and if, on the contrary, it should traverse it at too obtuse an angle,
it would depress and contract it. Experience has shown that in the majority of cases the mostfavorable angle at which the external current of air can be led into the flame varies between 35° and45°. We say in the majority of cases, for there are exceptions; this depends upon the combustive
materials and upon the conditions under which they enter the flame. The annexed figure shows theform adopted by the inventor for oil and kerosene lamps. As may be seen, the chimney consists oftwo cones, A and B, connected end to end by their small bases. The upper one, A, or divergent cone,
is constructed according to a variable angle, but one which, in order to produce its maximum effect,
ought not to differ much from 5°. This cone rests upon the convergent one, B, whose angle, as wehave said, varies between 35° and 45°. To the large base of this cone there is soldered a cylindricalpart, c, designed for fixing the chimney to the holder. The height given the divergent cone is
likewise variable, but a very beautiful light is obtained, when it is equal to six times the diameter ofthe contracted part. When the lamp is designed to be used in a still atmosphere, free from abrupt
currents of air, the height may be reduced to four times the diameter of the base, without the lightbeing thereby rendered any the less bright. As for the height to be given the convergent cone, B, thatis determined by the opening of the angle according to which it has been constructed. Finally, as a
general thing, the diameter of the small base should be equal to half the large base of the convergent
cone, B.
The new chimney should be placed upon the holder in such a way that the upper part of the wicktube, D, is a few millimeters beneath the base of the convergent cone. The height to be given thewick varies according to the lamp used. It is regulated so as to obtain a steady and regular
combustion. In oil lamps it must project about 1½ centimeters. If two lamps of the same size be
observed, one of which is fitted with the new chimney and the other with the old style, we shall be
struck with the difference that exists in the color of the flame as well as in its intensity. While in thecase of the cylindrical glass the flame is red and dull, in that of the circuit it is white and very
bright. This, however, is not surprising when we reflect upon the theoretical conditions upon which
the construction of the new chimney is based—the strong influx of air having the result of causing amore active combustion of the liquid, and consequently of raising to white heat the particles ofcarbon disseminated through the flame. As it was of interest to ascertain what the increase ofilluminating power was in a given lamp provided with the new chimney, Mr. Felix le Blanc
undertook some photometric experiments. The trials were made with a Gagneau lamp provided witha chimney of the ordinary shape, and then with one of Mr. Bayle's. The measurements were madeafter each had been burned half an hour. The light of the standard Carcel lamp being 1, there wasobtained with the Gagneau lamp with the ordinary chimney 1.113 carcels, and with the Baylechimney 1.404 carcels. Thus 1.113:1.404 represents the ratio of the same lamp with the ordinarychimney and with that of Bayle. Whence it follows that the light of the lamp with the old chimney
being 1, that with the new one is 1.26, say an increase of about 25 per cent. There is nothing
absolute about this figure, however. On kerosene lamps the new chimney, compared with thecontracted Prussian one, gives an increase of 40 per cent. in illuminating power, and the oil isburned without odor or smoke.
As it was of interest to see whether this increase in intensity was not due to a greater consumptionof oil, a determination was made of the quantity of the latter consumed per hour. The Gagneau
lamp, with the old chimney, burned 62.25 grammes per hour, and with the Bayle 63 grammes in thesame length of time.

It may be concluded, then, that the increase in light is due to the special form given the chimney.
This new burner is applicable to gas lamps as well as to oil and petroleum ones.
The effects obtained by the new chimney may be summed up as follows: increase in illuminating
power, as a natural result of a better combustion; suppression of smoke; and a more active
combustion, which dries the carbon of the wick and thus facilitates the ascent of the oil. The
velocity of the current of air likewise facilitates the action of capillarity by carrying the oil to the topof the wick. Moreover, the great influx of air under the flame continually cools the base of thechimney as well as the wick tube, and the result is that the excess of oil falls limpid and unalteredinto the reservoir, and produces none of those gummy deposits that soil the external movements andclog up the conduits through which the oil ascends. Finally, the influx of air produced by thischimney permits of burning, without smoke and without charring the wick, those oils of poor
quality that are unfortunately too often met with in commerce.—