294 SCIENCE OF HOME AND COMMUNITY 



Directions, i. To show the buoyant force of water on a 

 sinking body, tie a string to a stone and weigh it in air by means 

 of a spring balance. Submerge the stone in water and weigh 

 it. How much has it lost ? To what is this loss due ? 



2. To show the buoyant effect of water on a floating body, 

 fill the overflow can as full of water as possible. Weigh the 

 catch bucket. Weigh the wooden cylinder. Place it on the 

 surface of the water in the overflow can and catch the overflow 

 in the catch bucket. Find the weight of the water in the catch 

 bucket. How does this compare with the weight of the block 

 of wood ? 



3. Put some shot in a test tube and float the tube in a dish 

 of water. Glass and shot are both heavier than water. Why 

 then does the tube float? Why do steel ships float? Catch 

 the overflow as in the previous experiment and compare with 

 the weight of the tube and shot. Add more shot. What hap- 

 pens to the tube? Remove some shot. What happens? 

 What fact does this illustrate about the loading and unloading 

 of a boat ? 



. .4. To;show the difference in the buoyant force of fresh and 

 salt water, put an egg in a dish of fresh water. What happens? 

 Put the egg in a strong solution of salt and water. What 

 happens? What causes the difference? In which body of 

 water would a boat sink deeper, in the Great Lakes or the At- 

 lantic Ocean ? Why ? 



Submarines. During the European War our attention 

 was specially called to submarines on account of the de- 

 structive use to which they were put. This use of the sub- 

 marine was especially brought home to the American people 

 when the Lusitania was sunk in 1915, killing more than a 

 thousand people, including many Americans. Some Ger- 

 man submarines crossed the ocean and came to an American 

 port bringing merchandise. The use that has been made 

 of these submarines shows how well perfected they have 

 v become.. It is a possibility of the near future that one may 

 travel across the ocean in a submarine submerged all the 



