36 SCIENCE PRIMERS. [MATERIAL 



is, that ships made of thick plates of iron riveted 

 together, and weighing many thousand tons, do not 

 go to the bottom. But they are nothing but our tin 

 canisters on a great scale, and they float because each 

 ship weighs less than a quantity of water of the same 

 bulk does. 



It is because of this property of water to bear up 

 things lighter than itself, and because of that other 

 property of being easily moved which the particles of 

 water have, that the sea, and rivers, and canals, are 

 such great highways for mankind. 



For there is nothing so heavy that it may not be 

 made to float in water, if the box which holds it is 

 large enough to make the weight of the whole less 

 than the weight of the same bulk of water. And 

 then, having once got the weight to float, the particles 

 of water are so easily moved, that the force of the 

 winds, or of oars, or of paddles, readily causes it to 

 slip through the water from one place to another. 



26. A Body which Floats in Water always 

 occupies as much Space beneath the level of 

 the Surface of the Water as is equal' to the 

 Volume of Water which weighs as much as 

 that Body ; in other words, it displaces its 

 own Weight of Water. 



A cubic inch of water weighs about 252 grains and a 

 half. Suppose that the tin box in the previous experi- 

 ment was square, and had the bulk of 100 cubic inches, 

 then the weight of a corresponding volume of water 

 would be 25,250 grains. If the box weighed 8,416 

 grains, just a third of its bulk would be immersed ; if 



