SCIENCE OF COMMON THINGS. 181 



Water-pipes often burst in winter. Bottom of a river rarely frozen. 



1191 Why is not the ice solid in these ruts ? why is there only a very 

 thin film or network of ice ? 



Because the earth absorbs most of the water, and 

 leaves only the icy film behind. 



1193 Why do water-pipes frequently burst in frosty weather? 



Because the water in them freezes, and (expanding 

 by frost) bursts the pipes to make room for its increased 

 volume. 



1193 Why does the earth crack in intense cold weather ? 



The moisture in the soil in the act of freezing ex- 

 pands^ and forces the particles asunder. The disrup- 

 tion of the earth is frequently accompanied with a loud 

 sound. 



1194 Does not water expand by heat as well as ly coldf 



Yes ; it expands as soon as it is more than 42, till it 

 boils / after which time it flies off in steam. 



1195 When does water begin to expand from cold? 



Yv r hen it is reduced to 40. Water is wisely ordained 

 to be an exception to a very general rule : it contracts 

 till it is reduced to 40, and then it expands till it 



freezes. 



The general rule is this : That cold condenses and contracts the volume 

 of nearly everything; but .water is not contracted by cold when it freezes 

 (which it does at 32). 



1196 Why does water expand when it freezes $ 



The expansion of water at the moment of freezing is 

 attributed to a new and peculiar arrangement of its 

 particles. Ice is, in reality, crystallized water, and dur- 

 ing its formation the particles arrange themselves in 

 ranks and lines which cross each other at angles of 60 

 and 120, and consequently occupy more space than 

 when liquid. This may be seen by examining the sur- 

 face of water in a saucer while freezing. 



1197' Why is the bottom of a river rarely frozen f 



Because water ascends to the surface as soon as it be- 

 comes colder than 42, aad (if it freezes) floats there till 

 it is melted. 



1198 Show the wisdom of the Creator in this wonderful exception to a 

 general law. 



