410 SOUND. 



Q. How FAST does SOUND TRAVEL ? 



A. About 13 miles in a minute, or 

 1142 feet in a second of time. 



Q. How fast does LIGHT TRAVEL? 



A. Light would go 8 times round 

 the whole earth, while sound is going its 

 13 miles. 



Q. Why are SOME things SONOROUS, and others 

 NOT? 



A. The sonorous quality of any 

 substance depends upon its hardness and 

 elasticity. 



Q. Why are COPPER and IRON SONOROUS, and 

 not LEAD ? 



A. Copper and iron are hard and 

 elastic; but as lead is neither hard nor 

 yet elastic, it is not sonorous. 



Q. Of what is BELL-METAL made ? 



A. Of copper and tin in the following 

 proportions : In every 5 pounds of bell- 

 metal, there should be 1 Ib. of tin, and 

 4 Ibs. of copper. 



Q. Why is this mixture of tin and copper used 



for BELL-METAL ? 



A. Because it is much harder and 

 more elastic than either of the pure 

 metals. 



