Common Science 



FIG. ii. The battleship is made of steel, yet it does not sink. 



than the object. It is the water or air being pulled 

 under the object by gravity, that pushes it up. There- 

 fore, if the air and water themselves weighed nothing, 

 of course they would be no heavier than the balloon 

 or the cork ; the air or water would then not be pulled 

 in under the balloon or cork by gravity, and so would 

 not push them up, or aside. 



Why iron ships float. When people first talked about 

 building iron ships, others laughed at them. " Iron 

 sinks," they said, " and your boats will go to the bottom 

 of the sea." If the boats were solid iron this would be 

 true, for iron is certainly much heavier than water. 

 But if the iron is bent up at the edges, as it is in a 

 dish pan, it has to push much more water aside before 

 it goes under than it would if it were flattened out. 

 The water displaced, or pushed aside, would have to 

 take up as much room as was taken up by the pan and 



