194 GUANO. 



which must be weighed after cooling. The less ash 

 is left behind^ the bette?^ is the guano. The best sorts 

 of Peruvian guano yield, from half an ounce, only 

 one drachm of ashes (30 to 33 per cent.) ; whereas 

 the inferior guanos that are now so often offered for 

 sale (for example, Patagonian, African, Saldanha 

 Bay, and Chili guanos) leave a residue of from 2J 

 to 3 drachms (60 to 80 per cent), and those inten- 

 tionally adulterated a still greater quantity of ashes. 

 Of genuine bird-manure, the bad as well as the good, 

 the ash is always white or gray; a yellow or red- 

 dish color indicates an adulteration with loam, sand, 

 earth, etc. 



This test is very simple, and at the same time very 

 reliable ; it rests upon the fact, that the azotized 

 combinations existing in guano, and forming, as has 

 been demonstrated in a preceding section, its most 

 valuable ingredients, undergo combustion and vola- 

 tilization when subjected to heat. Here, too, the 

 difference of odor during the combustion is extreme- 

 ly characteristic. The vapors ascending from the bet- 

 ter specimens have a pungent smell, like hartshorn, 

 with a peculiar piquancy, almost like old Limburg 

 cheese (decayed) ; whilst those rising from inferior 

 varieties smell, on the other hand, like singed horn- 

 shavings or hair. 



The combustion may be undertaken on any hearth 

 or in any parlor stove, if there is no objection in the 

 latter case to the disagreeable odor which will be 

 diffused throughout the room. A brick should be 



