64 FIRST YEAR COURSE IN GENERAL SCIENCE 



a block of stone weighs 1,500 kilograms; a piece of iron, 

 much smaller, weighs 15 kilograms. The piece of iron is 

 much lighter than the block of stone. But, on the other 

 hand, 1 cubic centimeter of the stone weighs 3.5 grams; 

 1 cubic centimeter of iron weighs 7.8 grams. The iron has 

 more matter in a cubic centimeter, or a cubic inch, or a 

 cubic foot, than the stone has. The density of the iron is 

 greater. 



In the British system, in which the cubic foot is the unit 

 of volume and the pound the unit- of weight, the density of 



FIG. 26. PLATFORM SCALES 



This form of balance is an application of the lever. The pans or 

 platforms are at the end of a bar which is supported at the middle. 1. With 

 nothing on either platform, the bar is horizontal. Why? 2. Under what 

 other conditions will the bar be horizontal? 3. What is its position with 

 100 g. on one platform and 90 g. on the other? Why? 



a substance is the weight in pounds of one cubic foot of that 

 substance. One cubic foot of water weighs 62.5 pounds; 

 therefore the density of water is 62.5 pounds per cubic foot. 

 One cubic foot of marble weighs 168.5 pounds; therefore the 

 density of marble is 168.5 pounds per cubic foot. 



In the metric system, in which the cubic centimeter is the 

 unit of volume and the gram the unit of weight, the density 

 of a substance is the weight in grams of one cubic centimeter 



