98 FAEADAV 



only to empty it. The reason Is this: the wire, being once 

 wetted, remains wet ; the meshes are so small that the fluid is 

 attracted so strongly from the one side to the other as to 

 remain in the vessel, although it is porous. In like manner, 

 the particles of melted tallow ascend the cotton and get to 

 the top; other particles then follow by their mutual attrac- 

 tion for each other, and as they reach the flame they are 

 gradually burned. 



Here is another application of the same principle. You 

 see this bit of cane. I have seen boys about the streets, who 

 are very anxious to appear like men, take a piece of cane, 



and light it, and smoke it, as an 

 imitation of a cigar. They are 

 enabled to do so by the perme- 

 ability of the cane in one direc- 

 tion, and by its capillarity. If I 

 place this piece of cane on a plate containing 

 some camphene (which is very much like paraf- 

 fine in its general character), exactly in the 

 same manner as the blue fluid rose through 

 the salt will this fluid rise through the piece 

 of cane. There being no pores at the side, 

 the fluid can not go in that direction, but must 

 pass through its length. Already the fluid is 

 at the top of the cane; now I can light it and 

 make it serve as a candle. The fluid has risen 

 by the capillary attraction of the piece of cane, 

 just as it does through the cotton in the candle. 



Now the only reason why the candle does not burn all 

 down the side of the wick is that the melted tallow extin- 

 guishes the flame. You know that a candle, if turned upside 

 down, so as to allow the fuel to run upon the wick, will be put 

 out. The reason is, that the flame has not had time to make 

 the fuel hot enough to burn, as it does above, where it is 

 carried in small quantities into the wick, and has all the 

 effect of the heat exercised upon it. 



There is another condition which you must learn as regards 

 the candle, without which you would not be able fully to 

 understand the philosophy of it, and that is the vaporous con- 

 dition of the fuel. In order that you may understand that,, 



