On the Supposed Action of Light on Combustion. 217 



not too deep, there would be seen immediately over the orifice a 

 hollow depression which increases until it becomes a cone or funnel 

 the centre or lowest point of which is in the orifice, and the liquid 

 flows in lines directed towards the centre. In this condition of 

 the liquid a rotatory motion is necessarily imparted to it; and 

 this rapidly increases, because all the particles are approaching 

 the centre, and by virtue of their inertia they tend to maintain 

 the same velocity which they had in a larger circle, so that their 

 angular velocity (or the number of revolutions in a given 

 time) is constantly being increased. As the particles approach 

 the orifice they converge to a point beyond it, so that the liquid 

 in escaping is narrower or more contracted at the point to which 

 it converges than it is either before it arrives at that point, or 

 after it has passed it. But as this point in the phosphorus to 

 which the rotating lines converge, though fixed in or near the 

 tube, is being constantly shifted in the phosphorus by being- 

 drawn out and moulded in the tube, the converging lines are 

 also drawn out, and thus give the appearance of a double spiral. 

 Of course some of the lines are obliterated by the moulding 

 action of the tube, and are probably of a different texture as to 

 hardness as compared with the drawn-out lines. These flattened 

 or moulded portions first yield to the action of slow combustion, 

 and leave the harder drawn-out lines in relief. 



Highgate, N., 

 July 31, 1869. 



XXV. On the Supposed Action of Light on Combustion. 

 By Charles Tomlinson, F.R.S., F.C.S.* 



f I^IIE popular idea that "light puts out the fire" is so fixed, 

 J- that probably no conclusions drawn from actual experi- 

 ment are likely to disturb it, especially if they be adverse to the 

 notion. It is a matter of daily experience, people say, that if the 

 fire is nearly out and you put a screen before it, or draw down 

 the blind, or close the window-shutters, it will immediately 

 begin to revive. It is generally forgotten that afire which looks 

 dull or "out" in a well-lighted room will appear to be in tole- 

 rable condition in the same room when darkened. It only re- 

 quires to be "put together " to make it burn up, and it might 

 have done so just as well in the light. 



Experiments on this subject are not easy to make, on account 

 of the many disturbing causes. In an old volume of the c Annals 

 of Philosophy ' is an account of some experiments by Dr. 

 M'Keever, who took two portions of green wax taper, each 



* Communicated by the Author, having been read at the British Asso- 

 ciation at Exeter, August 20, 1869. 



Phil. Mag. S. 4. Vol. 38. No. 25-1. Sept. 1869. Q 



