1005. The value of guano as manure depends on 

 the ammonia which it contains, or the presence of 

 matter capable of forming ammonia by its slow putre- 

 faction, and on the presence of phosphoric acid. No 

 manure is more subject to fraudulent adulteration 

 than guano. One of the most common modes of 

 doing this is by the addition of earth or brickdust. 

 The presence of these substances may be roughly 

 ascertained in guano by burning a portion. The 



