68 FIELD, FOREST AND FARM 



the sea are all notorious for their insatiable appe- 

 tite. Constantly in search of fish, which they live 

 on, they spend the day exploring the surface of the 

 waters at immense distance from land. Nature has 



endowed them with 

 prodigious flying 

 power. To these in- 

 defatigable rovers an 

 aerial promenade of 

 some hundreds of 

 leagues before dinner 

 is a mere nothing. 

 Scattered during the 



Common Gull, or Mew-gull . . 



day in all directions 

 in quest of prey, they reach the islets in the evening 

 to spend the night, arriving in flocks so dense as 

 to darken the sky. Being well fed, thanks to their 

 foraging excursions, they cover the ground at night 

 with a thick layer of excrement. And as this has 

 been going on century after century ever since the 

 world was made, these deposits, piled one on another, 

 have at last become massive beds twenty or thirty 

 meters thick, and so hard, so compact, that to break 

 them it is necessary to use a pick or a petard, just as 

 one would in quarrying stone. Workmen operate 

 this dung mine, and vessels from all parts of the 

 world fetch cargoes of this valuable material, which 

 is called guano. This enormous mass of dung, which 

 has by the lapse of ages been turned into a sort of 

 whitish loam, gives Peru an annual revenue amount- 

 ing to sixty millions of francs. 



