Masterpieces of Science 



nate with the forcible ejection of heated matter 

 from the interior of the earth. A rent may be 

 produced at some weak point, and this crack 

 then serves for the passage of large volumes of 

 steam and other vapours, with showers of red-hot 

 ashes, accompanied or followed by streams of 



1 



FIG. 50. Diagrammatic Section of a Volcano 



molten rock. The solid materials are shot forth 

 into the air, and fall in showers around the mouth 

 of the orifice; where they form, by their accumu- 

 lation, a cone-shaped mound or hill. Such a hill 

 is called a volcano, or popularly a "burning 

 mountain. " It must be borne in mind, how- 

 ever, that it does not "burn," in % the sense in 

 which a fire burns, but it merely offers a channel 

 through which heated matter is erupted from 

 176 



