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THE NATIONAL GEOGRAPHIC MAGAZINE 



OLD TERRACES ON THE STEEP SIDES OF THE GORGE OF THE RIMAC, WHICH THE 



PERUVIAN FARMERS OF AN EARLY CIVILIZATION ENRICHED WITH 



THE GUANO GATHERED ON THE RAINLESS COAST 



The ancient Peruvians developed the practice of irrigation to a remarkable degree. 

 Under modern conditions, only the bottom, showing dark in the photograph, is under culti- 

 vation. Guano was conveyed from the islands to fertilize such interior farms (see text, 

 page S4i ). 



eggs and bodies of birds and the deposits 

 and the bodies of sea-lions. It may be 

 found mixed with gravel and sand in 

 very small proportion or sometimes to an 

 extent rendering it unprofitable to ex- 

 tract. 



Great beds of guano have been formed 

 upon islands of the Caribbean Sea ; upon 

 others off the coast of Africa ; and upon 

 still others of the southern and far Pa- 

 cific ; yet these guanos are scarcely com- 

 parable to Peruvian guano, for in the 

 moist climate prevailing upon such shores 

 the nitrogen is soon lost in the form of 

 ammonia, while the insoluble phosphates 

 remain to form a far less valuable "phos- 

 phatic guano." 



"Peruvian guano" is practically synony- 

 mous with nitrogenous guano and has 

 long been recognized as the best nitrog- 

 enous fertilizer — that is, as a fertilizer 

 of generally high nitrogen value in which 

 the nitrogen compounds are found in a 

 condition most readily assimilable by our 

 plants. 



peru's birds help to support humanity 



Nitrogen is a primary necessity to the 

 farmer. Whatever may be the impor- 

 tance of adding to the soil potash and 

 other mineral components of our food 

 and our clothing, there never exists a 

 doubt as to the fundamental importance 

 of nitrogen. 



