564 PLUCKER ON THE ACTION OF THE MAGNET 



depressed in the same manner as the flame of a stearine candle, 

 and at different elevations assumed the corresponding forms. 

 The combustion was increased, and the original dark violet colour 

 became of a beautiful yellow. 



24. The increase of the flame, which has always hitherto been 

 found to occur, evidently depends upon the flame of the source 

 from which it is supplied being brought nearer by the magnet. 

 The alcohol, the stearine and the sulphur are more rapidly con- 

 sumed on account of the increased heat. To ascertain specially 

 the cause of the production of the yellow colour of the flame by 

 the magnet, which did not occur in the combustion of the sul- 

 phur, alcohol without a wick was placed under the apices of the 

 poles in a thimble-shaped vessel of copper and ignited, thus 

 replacing the common spirit-lamp. The flame was then changed 

 in form as before, but without becoming coloured yellow. Hence 

 the yellow colour in the former experiment appears to have 

 arisen from carbonaceous particles having become detached from 

 the wick ; and this again is produced by the flame being pressed 

 down upon the wick by the excitation of the magnetism^ and 

 the wick thus partly carbonized. 



25. It was still a point of interest to examine the flaine of hy- 

 drogen, which, as is well known, merely consists of aqueous va- 

 pour at a red heat. The hydrogen gas was evolved in the ordi- 

 nary way from pieces of zinc and dilute sulphuric acid, and, on 

 turning a cock, issued from a glass tube drawn out to a fine 

 point, tlie aperture of which was placed beneath the middle of 

 the space between the apices of the poles, under a perpendicular 

 pressure of water, which at the commencement was 340 millims. 

 in height. After igniting it, the magnetism was excited. At 

 first, from the great force with which the gas escaped, no action 

 upon the flame was perceptible ; but as the pressure of the water 

 continued to diminish, the flame at the same time becoming 

 smaller, the effect soon became apparent, and the flame was driven 

 laterally and depressed exactly as in the former analogous cases. 



26. When we reflect upon the phaenomena which the different 

 flames have exhibited (14-25), all the various forms are expli- 

 cable on the assumption, that the mass of the flame is repelled 

 by the magnet, and that this repulsion principally takes place 

 from the axial line in all directions. The form of the flame be- 

 comes changed in consequence of external influences, in exactly 

 the same manner as in the case of a volume of gas enclosed in a 



