74 THE SUN'S GIFT OF HEAT 



made the production of fire easy and certain. It has been 

 one of the great factors in making life comfortable. The 

 earlier matches consisted of a splinter of wood tipped with 

 a mixture of sulphur, yellow phosphorus, potassium chlorate 

 or red lead, held together by glue. When struck on a rough 

 surface the heat of friction was sufficient to ignite the phos- 

 phorus, thus causing the other materials to burn and the 

 splinter of wood to catch fire. 



It was soon found that the use of ordinary phosphorus 

 was very dangerous to the matchmakers, causing a dread- 

 ful bone disease. For that reason, the use of ordinary 

 phosphorus in the making of matches has now been prac- 

 tically abolished, and a harmless compound containing 

 phosphorus is usually substituted in its place. But since 

 friction against any rough surface will ignite the ordinary 

 match, nibbling mice and busy-fingered children have 

 often started disastrous fires with them. Because of that 

 the safety match was invented, which will not ignite by 

 friction on any ordinary rough surface. 



On the tip of the safety match there is no phosphorus nor 

 phosphorus compound, but only substances that burn 

 readily and contain a great deal of oxygen. The side of the 

 .match box is used for a striking surface. It is coated with 

 several substances, among which is red phosphorus. The 

 only way red phosphorus can easily be ignited by friction is 

 to rub it with some substance that is rich in oxygen. The 

 oxygen-bearing materials on the tip of the safety match 

 strike a spark out of the red phosphorus, which in turn 

 ignites the match head. 



Saving Fuel. Experiment 26. (a) After closing the holes at 

 the bottom of a Bunsen burner, turn on the gas and light it. The 

 flame is smoky. Heat a piece of wire in it. It heats slowly. 



