Mr Blackadder cyii the Constitution of Flame. 2^5 



lias been applied, the instrument is removed from the flame, it 

 . is found to contain alcoholic vapour, and which, when lighted, 

 on being slowly expelled by the breath, gives a blue flame at 

 the point of the blowpipe. If, instead of performing suction 

 by the mouth, the tube, inserted in the flame, be connected 

 with a vessel full of mercury, and the latter be allowed slowly 

 to escape, any quantity of vapour may be collected from conical 

 flames. When an accurate analysis is to be made of this va- 

 pour, it is necessary to fill the tube as well as the vessel with 

 mercury, and to abstract the air that is mixed with the combus- 

 tible fluid. It is also to be recollected, that a small quantity of 

 air always remains between the surface of the mercury, and the 

 glass vessel. In making use of a blowpipe in the way described, 

 with the flame of a candle or oil lamp, it is preferable, for rea- 

 sons that will afterwards appear, to perform the suction by 

 means of a syringe, or a bag of elastic gum. In this case, a 

 dense white vapour is observed to fall in a continued stream, 

 into the hollow bulb of the instrument, the flattie at the same 

 time contracts, and when the extracted vapour is lighted, it 

 burns with a white flame. When this vapour is in the interior 

 of the flame, it is kept at a high temperature, and is then per- 

 fectly transparent, but the instant its temperature is very slight- 

 ly reduced, as by touching the upper part of the wick with the 

 point of a small wire, it acquires a milky whiteness ; and hence, 

 when falling in a stream from a tube, it is so dense as to resem- 

 ble an opaque hquid. By means of an Argand lamp, without a 

 wick, the burner being made of Reaumeur's porcelain, this va- 

 pour may be procured pure and in great abundance ; but the 

 following method is more simple, and is abundantly productive. 

 A glass-vessel, having a wide mouth, and a perforation in its 

 bottom, is converted into a lamp with a circular wick. The cen- 

 tral canal which supports the wick is made of glass-tube, not less 

 than the eighth of an inch in diameter, and which is left project- 

 ing below the body of the lamp. On lighting a lamp of this de- 

 scription, air does not rise through the tube ; but, in the course 

 of a few seconds, masses of dense white vapour are seen falling 

 down through it, and these are soon followed by a continued 

 stream, which flows copiously from its lower orifice. On some 

 occasions it is discharged in the form of beautiful rings, or loop- 



JULY OCTOBER 18^6. P 



