BOILING WATER. 113 



the surface of the water. When water 

 simmers, the bubbles collapse beneath the 

 surface) and the steam is condensed to 

 water again : but when water boils, the 

 bubbles rise to the surface, and steam is 

 thrown off. 



Q. Why does a KETTLE SING when the water 

 simmers ? 



A. Because the air (entangled in the 

 water) escapes by fits and starts through 

 the spout of the kettle ; which makes a 

 noise like a wind instrument, when it is 

 blown into. 



Q. Why does NOT a kettle SING, when the 

 water BOILS ? 



A. As all the water is boiling 

 hot, the steam meets with no impediment, 

 but freely escapes in a continuous stream. 



Q. When does a kettle sing most ? 



A. When it is set on a hob to boil. 



Q. Why does a kettle SING MORE when it is 

 set on the SIDE of a fire, than when it is set in the 

 MIDST of the fire? 



A. When the kettle is set on the hob 

 to boil, the heat is applied very partially: 

 one side is hotter than the other, and 

 therefore the steam is more entangled. 



