BURNERS. 191 



burner is turned up high, the air which rushes through the interior ring 

 becomes decomposed before it can reach the air on the top of the flame, 

 which consequently burns in one undivided mass, the gas being in part un- 

 consumed, the products unconverted, and carbon deposited abundantly. 



If an excess of air is admitted, it would appear at first to be of no conse- 

 quence, but we shall find upon examination that the quantity of nitrogen 

 accompanying this excess has a tendency to extinguish the flame, while it 

 takes no part in the elective affinity constantly going on between the several 

 elementary gases, viz. hydrogen, oxygen, and the vapour of carbon ; and also 

 that the quantity of atmospheric air passing through the flame unchanged, 

 tends to reduce the temperature below that necessary for ignition, and there- 

 fore to diminish the quantity of light. For the proper combustion of the 

 gas, neither more nor less air than the exact quantity required for the forma- 

 tion of carbonic acid and water can be admitted through the flame without 

 being injurious. It is not possible practically to regulate the supply of air to 

 such a nicety, we therefore prefer to diminish the quantity of light by having 

 a slight excess of air rather than to produce smoke by a deficiency, the former 

 being unquestionably the least evil. 



In the year 1815, Mr. Clegg and Mr. Grafton commenced a series of experi- 

 ments upon the best form of burner, the principal object in view being to 

 regulate the supply of air to the flame. They found that the pressure given 

 to the upward rush of air through a glass chimney eight inches high, when 

 the interior air was highly rarefied, was equal to a head of water about three- 

 twentieths of an inch, and that a concentric ring having an area of one-fourth 

 of an inch admitted thirty cubic feet of air in one hour with the above press- 

 ure. This served as some data upon which to construct a burner ; for, by 

 knowing the quantity of gas it consumed, the exact quantity of air requisite 

 for its entire combustion could be allowed to pass through the flame. 



The woodcut Fig. 40 represents the kind of burner finally determined upon 

 as the best. The burner itself was an Argand one inch in diameter within the 

 drilled ring of jets, which, with a flame three inches high, consumed five cubic 

 feet of gas in an hour. For the complete combustion of that gas, fifty cubic 

 feet of air are required. To regulate the admission of the air to the flame, 

 an exterior cone was supported upon the gallery bearing the glass chimney, 

 the space at the top being ^eth of an inch from the edge of the burner ; this 

 annulus admits thirty feet of air. The interior of the flame was supplied with 



