DENSITY AND SPECIFIC GRAVITY 



43 



are maneuvered under water by varying the weight of the boat 

 in a somewhat similar way. The spirit level used by carpenters 

 and masons consists essentially of a glass tube full of liquid, ex- 

 cept for a small bubble of air. This air being lighter than the 

 liquid, always comes to the top. When the tube in its setting 

 is placed on a level surface the bubble will of course come to 

 rest exactly in the middle of the tube. Any variation from 

 this position indicates a surface that is not level. 



TABLE OF DENSITIES 



Practical Exercises 



1. Fill a graduate half full of water, and drop into it any convenient 

 piece of metal, finding the volume by noting carefully the amount of 

 water it displaces. Then weigh the metal. Assuming that every cubic 

 centimeter of water displaced weighs a gram, does the weight of the 

 metal justify the specific gravity assigned to it in the table? 



2. Which is heavier gold or silver? How much heavier? 



3. The density of brass is 8.5. How many centimeters of water 

 would be necessary to exactly balance 4 cubic centimeters of brass? 



4. How many grams would 10 cc. of platinum weigh if the density 

 of platinum is 21.5? 



