Sound 189 



273. A rather slight contraction of a muscle lifts your arm a con- 



siderable distance. 



274. A player on a slide trombone changes the pitch of the notes 



by lengthening and shortening the tube while he blows 

 through it. 



275. Rain runs off a tar roof in droplets, while on shingles it soaks 



in somewhat and spreads. 



276. There is a sighing sound as the wind blows through the 



branches of trees, or through stretched wires or ropes. 



277. Sometimes a very violent noise breaks the membrane in the 



drum of a person's ear. 



278. As a street car goes faster and faster, the hum of its motor 



is higher and higher. 



279. If a street is partly dry, the wet spots shine more than the 



dry spots do. 



280. Molten type metal, when poured into a mold, becomes hard, 



solid type when it cools. 



