376 Mr. Wm. Lowry o)i the Combustion of Coal-Gas. 



tral and outer apertures were proportionally reduced, the 

 flame became bright and cylindrical. 



On shortening the glass chimney, more light was obtained 

 from a given quantity of gas; and on taking off the glass alto- 

 gether, less gas was consumed in proportion to the light given 

 out. 



A perforated plate was laid on the top of the glass chimney, 

 and the quantity of light was increased ; and the same effect 

 took place by using a glass whose diameter at top was equal 

 to the openings found most advantageous in the perforated 

 plate. 



On doubling the height of the glass chimney, the flame fell 

 to about one half of its former height. 



As all these experiments (except the last, which is the con- 

 verse of the rest) either reduce the quantity of air supplied 

 to the burner, or bring the gas in a greater body in contact 

 with that quantity, it appears to follow that a certain propor- 

 tion of air is necessary to be supplied to the volume of gas 

 emitted ; and that should the proportion exceed a certain limit, 

 the gas is consumed without giving out all the light it is ca- 

 pable of producing; the extreme of which is the explosive 

 mixture, by which a large quantity of gas may be consumed 

 in a moment, giving out almost no light. On the other hand, 

 if too little air is supplied, the brilliancy of the flame is de- 

 stroyed, and the gas passes off without being perfectly con- 

 sumed. I was thus led to conclude, that the proper propor- 

 tions lay between the two extremes ; and the difficulty appeared 

 to be, to determine the point most advantageous in oecono- 

 mizing the gas consistent with the brilliancy of the flame ; and 

 my inquiries were accordingly directed to the construction of 

 a burner which would combine the advantages of admitting 

 the proper quantity of air, and at the same time bring the gas 

 in the most favourable manner in contact with it. From va- 

 rious trials it seemed that the greatest effect was produced 

 when the holes were numerous, and rather large than small, 

 the centi'al aperture narrow, and the glass near the flame ; the 

 outer aperture being in such proportion to the inner as to keep 

 the flame cylindrical. This construction, however, when car- 

 ried to the extreme, is attended with some practical disadvan- 

 tages. Burners being often placed in exposed situations, the least 

 motion of the air brings the flame in contact with the glass, in 

 such a way as to produce smoke ; and the glass being intensely 

 heated, is more liable to be broken. I found it answered the 

 purpose fully as well to enlarge the air aperture, making the 

 glass-chimney rather wider and shorter, reducing in this man- 

 ner the speed of the air through it. Accordingly when I con- 

 structed 



