WHAT IS THE SUN MADE OF ? 457 



Did you ever see an old woman throw a pinch of salt upon 

 the fire ' to clear the fire/ as she said, before setting on the 

 gridiron ? Did you ever push, by design or inadvertently, a 

 bit of copper amongst burning coals or into a candle-flame ? 

 The evidence of the fireworks, the salt, and the copper wire, 

 all goes to prove one and the same thing namely, that each 

 and every metal, as a rule, burns, evolving its own peculiar 

 tint. What metals, or what composition of metals, enter into 

 ornamental fireworks, we will not here stop to investigate; 

 but let it be understoood that each metal communicates to 

 flame its special hue. 



The second and third illustrations (both very simple) are 

 quite sufficient for my purpose. The old woman's pinch of 

 salt should you witness that experiment again, if not, you 

 can perform it will be observed to tinge the fire yellow; 

 and so, if you dip a bit of string into some salt-and-water, 

 then dry it, and when dry plunge it into the flame of a 

 candle, the flame will acquire the same peculiar tint of yellow. 

 And so, if, cross-questioning nature still, you take some of 

 that beautiful and very curious metal which enters into the 

 composition of sea-salt, and which is ' sodium,' if you take 

 some of that metal sodium, and set fire to it in a small pla- 

 tinum spoon, it also the metal sodium will be seen to burn 

 with a flame having the same tint of yellow. 



Similarly, the experimenter would find were he to take 

 the trouble of performing the experiment that copper, and 

 every preparation of copper, burns with a green flame. In 

 order to perceive the distinctive tints evolved by respective 

 metals undergoing combustion, no apparatus is necessary; 

 but it is only by the aid of an electric lamp and a triangular 

 prism that the full beauty of the tint can be made manifest. 

 Then will it be seen that sodium, when burned in a little 

 charcoal crucible within the electric lamp, develops, on the 

 yellow portion of the spectrum, a still yellower band ; that 

 copper, similarly burned, produces on the green part of the 



