316 Common Science 



When things do not burn up completely, the carbon 

 may be left behind as charcoal. That is what happens 

 when food " burns " on the stove. But if anything 

 burns up entirely, the carbon or charcoal burns too, 

 passing off as the invisible gas, carbon dioxid, just as 

 the hydrogen burns to form steam or water. 



It is because almost every fuel forms water when it 

 burns, that we find drops of water gathering on the out- 

 side of a cold kettle or cold flatiron if either is put directly 

 over a flame. The hydrogen in the fuel combines with 

 the oxygen of the air to form steam. As the steam 

 strikes the cold kettle or iron, it condenses and forms 

 drops of water. 



Nothing ever destroyed. One important result of the 

 discovery that burning is only a combining of oxygen with 

 the fuel was that people began to see that nothing is 

 ever destroyed. There is exactly as much carbon in the 

 carbon dioxid that floats off from a fire as there was in 

 the wood that was burned up ; and there is exactly 

 as much hydrogen in the water vapor that floats off from 

 the fire as there was in the wood. Chemists have 

 caught all the carbon dioxid and the water vapor and 

 weighed them and added their weight to the weight 

 of the ashes; and they have found them to weigh 

 even more than the original piece of wood, because 

 of the presence of the oxygen that combined with them 

 in the burning. 



If everything in the world were to burn up, using 

 the oxygen that is already here, the world would not 

 weigh one ounce more or less than it does now. All 

 the elements that were here before would still be here ; 



