34 GENERAL SCIENCE 



The Measurement of Volume. All bodies have three 

 dimensions, and if the shape of the body to be measured 

 is regular, it will be easy to measure the length, breadth, 

 and thickness and compute the volume. If the solid is 

 irregular, it is necessary to use other means in determining 

 the volume of space it occupies. When a solid is immersed 

 in a liquid, it displaces its own volume of the liquid, and 

 this means may be used in determining the volume of 

 such solids as cannot be accurately measured. Can you 

 devise a method of determining the volume of a solid which 

 floats in water ? 



Experiment 2. Determine the volume of a cylinder of wood by 

 first measuring it with a ruler and then by the displacement method. 

 How do the two determinations compare ? 



Measurement of Mass. Mass must not be confused 

 with volume. The measurement of mass simply means 



that we shall de- 

 termine the weight 

 of an object by 

 comparing it with 

 some standard. We 

 are able to detect 

 differences in weight 

 by our muscular 

 sense if the differ- 

 ences are great 



FIG. 27. Common Tip Scales or Balances. 



enough, but we 



should not care to rely upon the judgment of the grocer 

 who sold his sugar by weight as estimated by his muscles. 

 For this work a balance is used (Figure 27). If the arms 

 of the balance are of equal length, the weights used must 

 be as heavy as the object to be weighed. The object to 

 be weighed is then placed on one side and the weights 



