314 AIR. 



wind from 20 to 60. A hurricane from 

 80 to 100 miles an hour. 



Q. How is the VELOCITY of WINDS ascer- 

 tained ? 



A. By observing the velocity of the 

 clouds, and by an instrument for the 

 purpose. 



This instrument is called an ANEMOMETEB. 



Q. How is the VELOCITY of the CLOUDS 

 ascertained ? 



A. By observing the speed of their 

 shadow along the ground; which is 

 found in a high wind to vary from 20 to 

 60 miles an hour. 



Q. Why is there always a strong DRAUGHT 

 through the KEYHOLE of a door ? 



A. As the air of the room we occupy 

 is warmer than the air in the hall, there- 

 fore the cold hall air rushes through the 

 keyhole into the room, and causes a 

 draught. 



Q. Why is there ahvays a strong DRAUGHT 

 UNDER the DOOR, and through the crevice on each 

 side ? 



A. The cold air rushes from the hall 

 under the door, &c. into the room, to 



