GUANO. 193 



rieties that are brought from Peru and Chili, is a 

 smooth and uniform powder, weigh out two ounces, 

 spread it upon paper, and let it lie for two days in a 

 moderately warm place, in summer in a dry and airy 

 situation, in winter in a warm room or chamber, in 

 order that the air may dry it. What it may then 

 have lost in weight must be esteemed mere surplus 

 moisture. Many sorts of guano are so moist as to 

 lose by this gentle drying from three to four drachms 

 (20 to 24 per cent.) in their weight. 



If the guano, as mostly happens in the Patago- 

 nian and African varieties, is not a smooth and uni- 

 form powder, then, in order to obtain a mixture as 

 uniform as possible, before weighing off and drying a 

 given quantity, the lumps, which have frequently an 

 altogether different composition from that of the 

 powdery portions, must be broken in pieces and 

 pulverized. In like manner pains must be taken 

 that stones, feathers, etc., when they are present, be 

 equally distributed throughout the entire mass. 

 Since these stones are often so firmly stuck over 

 with the guano that they can only be separated with 

 difficulty from the latter by scraping, it is advisable 

 to pour hot water over a distinct portion in some 

 convenient vessel, and to let it soften by standing 

 for a night, upon which stones and sand will remain 

 behind after agitation and washing with water. 



2. Combustion. Pour half an ounce of the guano 

 to be examined into an iron spoon, and place it upon 

 red-hot coals until a white or grayish ash is left, 

 17 



