Section of Chemistry and Electricity. 405 



size and more numerous than usual. When the axis of the conical 

 air-tube is parallel with that of the burner, the direction of each 

 separate jet of flame from the holes in the burner is also parallel to 

 the same while the air-tube and burner are respectively concentric ; 

 but if, while they remain concentric, the axis of the air-tube be in- 

 clined to that of the burner, a far more singular effect ensues : each 

 separate jet of flame now in retracting describes a spiral round the 

 internal surface of the burner, making from one third to perhaps 

 one half a revolution. 



If the conical air-tube, while still inclined as above, be now brought 

 into contact with that side of the burner towards which it is inclined, 

 the obliquity of the spiral is much lessened ; but the flame is so 

 much retracted at the side of the burner opposite the air-tube that it 

 makes its appearance out at the lower end of the burner. The same 

 effects are produced whether the burners are vertically, up or down, 

 or horizontal, or inclined at various angles, subject to merely the 

 disturbances produced by the ascent of the neighbouring currents 

 of heated air. 



The effects do not seem to depend upon difference of temperature 

 between the current of air and the flame, as no change is produced 

 by heating the former to upwards of 600° Fahrenheit, neither does 

 the angle of the cone seem to be very essential, except it be so great 

 as to nearly stop the aperture of the burner. A cylindrical tube 

 answers equally well with a cone, but an inverted cone, that is, a 

 tube terminating with an enlargement, will not produce the effects. 

 Tubes of various other forms produce corresponding variations 

 of the principal phaenomena. A large flat disc, with an aperture 

 just large enough to admit the burner, placed close to its perforated 

 extremity, so as to prevent the passage of external currents parallel 

 to the internal current of air, does not change the effects. 



The retraction is considerably lessened, however, by stopping up 

 the space at the lower end of the burner, between it and the air- 

 tube, but is not wholly destroyed. 



Another singular fact connected with these remains to be men- 

 tioned : if a glass or copper tube, of about three eighths of an inch 

 greater diameter than that of the burner externally, be placed over 

 it, the same sonorous effect is produced as in the well-known ex- 

 periment of the combustion of pure hydrogen, but much louder ; 

 indeed, the copper tube used, which was eighteen inches long and 

 one and three eighths inches diameter, emitted a most overpowering 

 sound. Length of tube produced no variation in the state of the 

 flame, nor did increase of diameter over the above limits, although 

 both produced of course a change of musical note; but if the dia- 

 meter of the tube, whether of glass or copper, was reduced to very 

 nearly that of the external diameter of the burner, on approach- 

 ing the end of the tube with the burner, the retractile flame was 

 drawn forward, and, unless skilfully managed, was drawn out or 

 extinguished at the moment the burner entered the tube ; if, how- 

 ever, the introduction was successfully effected, the moment the 



