214 RADIATION. 



Q. WHERE does the WARM vapour of the 

 carnage come from ? 



A. The warm breath and insensible 

 perspiration of the persons riding in the 

 carnage, load the air of it with warm 

 vapour. 



Q. Wliat is the cause of the pretty FROST- 

 WORK seen on bed-room WINDOWS in winter-time ? 



A. The breath and insensible per- 

 spiration of the sleeper (coming in 

 contact with the ice-cold window) is 

 frozen by the cold glass, and forms 

 those beautiful appearances seen in our 

 bed-rooms in a winter morning. 



Q. Why is the GLASS of a window colder 

 than the WALLS of a room ? 



A. Glass is a very excellent radiator; 

 and, therefore, most rapidly parts with 

 its heat. 



Q. Why is a TUMBLER of cold WATER made 

 quite DULL with mist, when brought into a room 



FULL of PEOPLE ? 



A. Because the hot vapour of the 

 room (coming in contact with the cold 

 tumbler) is condensed upon it; and 

 changes its invisible and gaseous form 

 for that of a thick mist. 



