130 



LESSONS m CHEMISTRY. 



The above analysis is interesting, as exhibiting the true 

 composition, and very complex nature of this curious deposit ; 

 but it is obvious, that for agricultural purposes, a different 

 kind of analysis is required, in which the amount of the 

 various substances, which give this manure its peculiar value, 

 may be clearly understood by the farmer. Accordingly, in 

 estimating the value of a sample of guano, the method which 

 is followed in the laboratory of the Chemico- Agricultural 

 Society, is to furnish the farmer with a clear statement of 

 the per centage of water, organic matters, with the amount 

 of ammonia which they are capable of yielding by decompo- 

 sition ; phosphates of lime and magnesia, and substances like 

 common salt (chloride of sodium) and gypsum, which, though 

 valuable for the food of plants, can be more economically 

 supplied in other ways. 



192. The following table exhibits the composition of four 

 samples of guano lately sold in Belfast, 100 parts of each 

 sample contained respectively: — 



