60 CHEMICAL ACTION. 



Q. What are BLACKS ? 



A. When the hot air of the chimney 

 has been cooled by the external air, it can 

 no longer buoy up the solid smoke ; so 

 it falls to the earth in condensed flakes, 

 called " blacks." 



Q. Why are there NO BLACKS in the smoke of 

 a RAILWAY engine ? 



A. The smoke of a railway engine 

 consists chiefly of watery vapour, which 

 dissolves in air, as sugar does in water; 

 but the smoke of a common chimney 

 consists of small fragments of unburnt 

 fuel. 



Q. Why does a " COPPER HOLE" DRAW up 

 more fiercely than an OPEN stove ? 



A. As the air, which supplies the 

 copper hole, must pass through the furnace, 

 it becomes exceedingly heated, and rushes 

 up the chimney with great violence. 



Q. What produces the ROARING noise made 

 by a COPPER-HOLE fire ? 



A. Air rushing rapidly through the 

 crevices of the iron door, and up the 

 chimney flue. 



Q. Why is the ROAR LESS, if the copper-hole 

 DOOR be thrown OPEN ? 



