96 FARADAY 



fluid below, and do not encroach on the cup at the sides. I 

 can not imagine a more beautiful example than the condition 

 of adjustment under which a candle makes one part subserve 

 to the other to the very end of its action. A combustible 

 thing like that, burning away gradually, never being intruded 

 upon by the flame, is a very beautiful sight, especially when 

 you come to learn what a vigorous thing flame is what 

 power it has of destroying the wax itself when it gets hold 

 of it, and of disturbing its proper form if it come only too 

 near. 



But how does the flame get hold of the fuel? There is a 

 beautiful point about that capillary attraction.^) "Capil- 

 lary attraction ! " you say " the attraction of hairs." Well, 

 never mind the name; it was given in old times, before we 

 had a good understanding of what the real power was. It is 

 by what is called capillary attraction that the fuel is conveyed 

 to the part where combustion goes on, and is deposited there, 

 not in a careless way, but very beautifully in the very midst of 

 the centre of action, which takes place around it. Now I am 

 going to give you one or two instances of capillary attrac- 

 tion. It is that kind of action or attraction which makes two 

 things that do not dissolve in each other still hold together. 

 When you wash your hands, you wet them thoroughly; you 

 take a little soap to make the adhesion better, and you find 

 your hands remain wet This is by that kind of attraction 

 of which I am about to speak. And, what is more, if your 

 hands are not soiled (as they almost always are by the usages 

 of life), if you put your finger into a little warm water, the 

 water will creep a little way up the finger, though you may 

 not stop to examine it I have here a substance which is 

 rather porous a column of salt and I will pour into the 

 plate at the bottom, not water, as it appears, but a saturated 

 solution of salt which can not absorb more, so that the action 

 which you see will not be due to its dissolving any thing. 

 We may consider the plate to be the candle, and the salt the 

 wick, and this solution the melted tallow e (I have colored 



* Capillary attraction or repulsion is the cause which determines the ascent 

 or descent of a fluid in ft capillary tube. If a piece of thermometer tubing, 

 open at each end, be plungea into water, the latter will instantly rise in the 

 tube considerably above its external level. If, on the other hand, the tube 

 be plunged into mercury, a repulsion instead of attraction will be exhibited, 

 and the level of the mercury will be lower in the tube than it is outside. 



