48 Trees, Stars, and Birds 



volume of water. This is equivalent to saying that its 

 density is one third that of water. Densities are usually 

 expressed by decimals. Thus the density of arbor 

 vitae is .325. Is that more or less than one third? 



Place in water various kinds of seasoned wood and 

 notice their relative densities. Slender pieces may be 

 floated in a jar that is narrow enough to keep them up- 

 right ; other pieces can be laid flat on the water. When 

 the piece has come to rest, measure carefully the distance 

 between the lower end of the piece of wood and the 

 upper surface of the water. Compare this with the 

 whole height or thickness of the piece. If three fourths 

 of the wood is under water, it has a density of f or .75. 

 In determining density in this way, does it matter if 

 the piece of wood is not regular in form? How could 

 you prevent water from soaking into the wood during 

 the experiment? 



Some kinds of wood are so much lighter than others 

 that you can judge of their relative density by merely 

 picking up pieces of them and noticing their size and 

 weight. Try this with two pieces of nearly the same 

 density ; then determine the density of each piece by 

 the method given above. 



With a knife test the hardness of several kinds of 

 wood. Are the harder ones always the denser ones? 

 Make a list of several kinds of wood that are valued for 

 fuel. Are they valued because they burn fast or long? 

 Are they as dense as those of less value for fuel ? 



Why water-logged wood sinks. The material of 

 which wood is composed is heavier* than water, and a 

 piece of wood floats only because of the air spaces it 





