The Story-Book of the Fields 



expansion. So the cylinder is cracked be- 

 cause ice was formed inside it. 



I can quote an experiment which will 

 show the irresistible power of ice when it 

 forms and expands in a closed space. What 

 is stronger than a cannon ? It is made of 

 bronze, a metal almost as impregnable as 

 iron. It weighs several tons and is more 

 than a hand-breadth in thickness. A small 

 bag of gunpowder and a cannon-ball which 

 you could hardly lift are placed inside. The 

 gunpowder is ignited, there is an explosion 

 like a clap of thunder, and the iron cannon- 

 ball is hurled for a league, and even farther. 

 So you may judge of the resistance offered 

 by this terrible machine. 



Well, the power of the pressure of ice has 

 been tried in a cannon. A cannon is filled 

 with water ; then its mouth is stopped with 

 a solid plug of iron, screwed in so that it 

 cannot give way. This cannon is exposed 

 to the cold during a very severe winter's 

 day. The water turns to ice, and soon the 

 gun is cracked from end to end, the ice 

 projecting through the crack. After this, 

 how can we be surprised that the cylinder 

 of a pump should be broken by the pressure 

 of ice, when a cannon is rent as easily as a 



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