WIND. 291 



warmed by the fire, &c., it ascends; and 

 (floating about the upper part of the 

 room) some of it escapes through the 

 crevice at the top of the door, and thus 

 produces a current of air outwards (into 

 the hall). 



Q. Why icoidd the flame be bloim INWARDS 

 (into the ROOM), if the candle icere held at the 

 BOTTOM of the door ? 



A. Because after the warm air of the 

 room has ascended to the ceiling, or 

 made its escape into the hall, &c., a 

 partial, vacuum is made at the bottom of 

 the room ; and cold air (from the hall) 

 rushes under the door to supply the void. 



Q. W hat is meant by a "partial VACUUM 

 being made, at the BOTTOM of the ROOM?" 



A. A vacuum means a place from 

 which the air has been taken : and a 

 "partial vacuum" means, a place from 

 which a part of its air has been taken 

 away. Thus when the air on the floor 

 ascends to the ceiling, a partial vacuum is 

 made on the Jloor. 



Q. And how is the VACUUM filled UP again ? 

 A. It is filled up by colder air 9 which 



ca 2 



