no Common Science 



it cooled, and took very much less space. This left 

 a vacuum or empty space in the flask. What pushed 

 the balloon into the empty space ? 



How steam makes an engine go. The force of steam 

 is entirely due to the fact that steam takes so much 

 more room than the water from which it is made. A 

 locomotive pulls trains across continents by using this 

 force, and by the same force a ship carries thousands of 

 tons of freight across the ocean. The engines of the 

 locomotive and the ship are worked by the push of 

 steam. A fire is built under a boiler. The water is 

 boiled ; the steam is shut in ; the only way the steam 

 can get out is by pushing the piston ahead of it; the 

 piston is attached to machinery that makes the locomo- 

 tive or ship move. 



One theory about the cause of volcanoes. The water 

 that sinks deep down into some of the hot parts of the 

 earth turns to steam, takes up more room, and forces 

 the water above it out as a geyser. It is thought by 

 some scientists that volcanoes may be started by the 

 water in the ocean seeping down through cracks to hot 

 interior parts of the world where even the stone is 

 melted ; then the water, turning to steam, pushes its way 

 up to the surface, forcing dust and stone ahead of it, and 

 making a passage up for the melted stone, or lava. The 

 persons who hold this view call attention to the fact 

 that volcanoes are always in or near the sea. If this is 

 the true explanation of volcanoes, then we should have 

 no volcanoes if steam did not take more room than does 

 the water from which it comes. 



Here is a very practical fact about boiling water 



