18 FIELD, FOREST AND FARM 



from the depths of the mountain. The crater throws 

 up into the air a lofty column of smoke, dark by 

 day, fiery red at night. All at once the mountain is 

 rent and vomits up through the crevices a stream of 

 fire, a current of melted rock, or lava. Finally the 

 volcano quiets down ; the source of the terrible flood 

 dries up. The streams of lava harden and cease 

 running; and after a lapse of time which may be 

 years they become quite cold. Now what is to be- 

 come of this enormous bed of black stone similar in 

 character to the slag from a forge? What will this 

 sheet of lava covering an area of several square 

 miles produce? 



"This desolate, blasted expanse seems destined 

 never to be clothed with verdure. But in any such 

 asumption one would be mistaken. After centuries 

 and centuries a vigorous growth of oaks, beeches, 

 and other large trees will have taken root there. In 

 fact, you will see that air, rain, snow, and, above all, 

 frost attack in turn the hard surface of the lava, 

 detach fine particles from it, and slowly produce a 

 little dust at its expense. On this dust there will 

 spring into being certain strange and hardy plants, 

 those white or yellow patches, those vegetable in- 

 crustations, calculated to live on the surface of stone 

 and known as lichens. These lichens fasten them- 

 selves to the lava, gnaw it still more, and in dying 

 leave a little mold formed from their decaying re- 

 mains. On this precious mold, lodged in some cav- 

 ity of the lava, there is now a growth of mosses 

 which perish in their turn and increase the quantity 



