LIQUEFACTION. 127 



Q. Why are METALS MELTED by the heat of 

 FIRE? 



A. The heat of the fire (entering the 

 solid metal) forces its particles asunder, 

 till their attraction of cohesion is suffici- 

 ently overcome, to convert the solid metal 

 to a liquid. 



Q. Why is WATER converted to STEAM by the 

 heat of FIRE ? 



A. The heat of the fire (entering the 

 water) divides its globules into very 

 minute bubbles, which (being made lighter 

 than air) fly off from the surface in the 

 form of steam. 



Q. Why does not WOOD MELT, like metal ? 



A. Because the heat of the fire 

 decomposes the wood into gas, smoke, and 

 ashes; and the different parts separate 

 from each other. 



Q. What is meant by VAPORIZATION ? 



A. The conversion of liquid into 

 vapour; as water is converted into vapour 

 by the heat of the sun. 



Q. What are CLOUDS ? 



A. Moisture evaporated from the 

 earth, and collected in the upper regions 

 of the air. 



