296 SCIENCE OF HOME AND COMMUNITY 



United States Government made an appropriation to be 

 used for the construction of submarines for the navy, and 

 decided to adopt the Holland type. The first Holland was 

 completed as a torpedo boat in 1900. These have been 

 greatly improved and have been adopted by the more impor- 

 tant navies of the world. 



How they rise and sink. Submarines are now made so 

 that they can run either on the surface or submerged. They 

 are made to sink by admitting water to tanks, and can be 

 made to dive by the action of the propeller and a horizontal 

 rudder. They are made to rise again by pumping out the 



er/'s cope 

 irf"/ask 



Watertight Hatch 



awsePipe 

 Torpedoes 



Cap of 

 -Torpedo 



Tubes 



^Torpedo Tube 

 ne Tanks 

 ^Batteries 

 Main Bat/ast Tanks 1 ^Circt//arl3voyancjr Tank 



FIG. 117. Sectional view of submarine (Holland type). 



water. The depth to which they sink is indicated by means 

 of gauges. The shell of the boat is made of strong steel so 

 as to withstand the tremendous pressure of the water far 

 below the surface. 



DEMONSTRATION 22 



Purpose. To see how the submarine is made to rise and sink. 



Apparatus. Large-mouth bottle, rubber stopper with two 

 holes, glass tubing, and rubber tube. 



Directions. Fill the bottle with water. Push a piece of 

 glass tubing through one of the holes in the rubber stopper. 

 Push one end of the rubber tubing over the glass tube. Put 

 the stopper in the bottle and put the bottle in a dish of water. 

 Blow through the rubber tubing till the water is forced out of 

 the bottle. What happens to the bottle? Why? Fill the 



