Mr Blackadder oti the Constitution of' Flame. 



body. The flame of a spirit-lamp, and a stream of cold air, 

 from a blowpipe, have the same effect as a solid body, in causing 

 the white hght to disappear *. If a solid body, such as the end 

 of a wire, be passed through the opaline brush, so as to come 

 into contact with the part of the flame from which the latter 

 proceeds, there is observed from the point of the wire upwards, 

 a line, in which the quantity of white light is very distinctly in- 

 creased ; but on carrying the point of the wire into the interior 

 of the flame, the line which was in the former instance rendered 

 more luminous, is now rendered transparent, and is altogether 

 deprived of white light ; so that on passing the wire quite through 

 the flame, the latter appears as if mechanically divided into two 

 parts. By greatly diminishing the force of the current of air, 

 as it impinges on the lower part of a flame, that part of the lat- 

 ter, which, in ordinary circumstances, is altogether of a blue co- 

 lour, becomes nearly as luminous as the rest of the flame. This 

 may be illustrated, by causing a small current of air to pass in a 

 transverse direction, and at a small distance, from the base of 

 the flame, or by bringing the extremity of a small tube near to 

 it, and applying suction. The same effect is produced by in- 

 creasing the supply of vapour at the lower part of the flame. 

 Thus, when a small metallic ball is connected with the orifice of 

 a burner without a wick, or when a double burner, the one with- 

 in the other, is used, the usual blue ligl?t, at the base of the 

 flame, is scarcely perceptible. In both these cases an unusual 

 supply of vapour is produced at the base of the flame. 



It was stated on a former occasion, that, when a vessel of wa- 

 ter was placed under a blue spirit-flame, and a solid body, near- 

 ly at a red heat, was introduced into it, the small particles of 

 water that were thus impelled on the exterior surface of the flame 

 caused an extrication of yellow light. It was also stated, that, 

 when small particles of water, driven by a simple mechanical im- 

 pulse, impinge on a blue flame, no yellow light Was given out. 

 Particles of water miry be thus discharged, by giving a whirl- 

 ing motion to a moist body, and in various other ways, with- 

 out obviously modifying the flame with which they come into 



• Hence a lamp, with concentric wicks, as hitherto constructed, is not likely to 

 afford the degree of illumination that might be expected from the increased sur- 

 face of flame and consumption of oil. It is better adapted to afford an increase of 

 heat than of light. 4 



