748 GUANO 



Peruvian . . 25' 12 



Angamos . . 20'25 



Ichaboe . ,31*00 



Patagonian . . 47'4 



SaldanhaBay . . 55"84 



Kooria Mooria . 15'66 



These facts are very suggestive as showing how guano, by exposure to air and 

 moisture, has the ammoniacal salts washed out, at the same time, as a consequence, 

 increasing the ratio of phosphates. 



Organic Matter. The amount of organic matter in guano, other than ammonia and 

 its salts, is of no great importance in estimating its value as a manure. Not unfro- 

 quently the amount of organic matter, containing uric acid or ammoniacal salts, is 

 stated in analyses, as organic matter ' rich in ' or ' containing ammonia ; ' but it is 

 obvious such analyses are nearly worthless, the value of the guano depending essen- 

 tially on the quantity of nitrogen, either existing as ammoniacal salts or capable of 

 being converted into them. Good guano contains on an average about 50 per cent, of 

 ash (mineral matter) and 50 per cent, of combustible (organic) matters. 



Sand. The knowledge of the proportion of sand in a guano is of some importance 

 as determining its purity or otherwise. It is easy to understand how a deposit like 

 guano, existing often near the sea-shore, and frequently on a sandy soil, should con- 

 tain a certain admixture of sand. Some specimens are almost free from it, and few 

 genuine specimens contain more than from 1 to 2 per cent. 



Common salt. The presence of common salt in a guano need not surprise us. It 

 is doubtless derived from the sea, partly through the medium of the birds themselves, 

 and partly from the evaporation of the salt spray continually driven upon the coasts 

 by the wind. It is variable in quantity, as we should expect from a knowledge of its 

 origin, ranging in samples of genuine guano from 1 to 5 per cent. Although common 

 salt has been shown ' to possess a certain power of absorbing ammonia, yet this is 

 but transient, and the efficacy of guano cannot be said to depend to any extent upon 

 the sea-salt present in it. The knowledge of its amount is of great importance, since 

 the guano is not unfrequently adulterated with salt. 



Water. Obviously the greater the amount of water present in guano, the smaller 

 will be the proportion of valuable constituents in a given weight. Genuine guano 

 contains on an average from 10 to about 20 per cent, of water. Many of the salts in 

 guano are likewise deliquescent, so that it has a tendency to become moist by ex- 

 posure to the air : and this tendency to absorb moisture is an element of value in the 

 manure, especially in dry seasons. 



Calculation of the money value of guano from the results of analyses. In a most 

 important and interesting paper ' On the Value of Artificial Manures,' 2 Mr. Way 

 arrives at certain money values for ammonia, phosphoric acid, and the various con- 

 stituents of guano and other manures, by a comparison with the cost of these several 

 compounds in their ordinary commercial salts. These numbers will be found most 

 valuable to the agriculturist in drawing his own conclusions respecting the value of 

 a guano or other manure from the results of analysis furnished to him by the chemist. 

 They are as follows : 







Ammonia 56 per ton. 



Potash 31 



Phosphate of lime (insoluble) 7 



Phosphate of lime (soluble) 32 



Organic matter 1 ., 



and the following example of their application may prove useful. 



Calculation of the money value of guano, as deducted from the cost of its several 

 constituents in their commercial salts, applied to the mean composition of Peru- 

 vian guano deduced by Mr. "Way from 78 analyses : 



100 tons contain 



Ammonia 16'5 at 56 per ton . . 930 



Organic matter .... 52*0 1 62 



Potash 3-5 31 . . 108 



Insoluble phosphate of lime . 23-0,, 7 . .161 



Soluble phosphate of lime . 7'0 32 . 224 



Value of 100 tons . . 1,475 

 Or, per ton . . 14J. 15*. 



1 A. B. Northcote, on the Function of Salt in Agriculture, Phil. Mag. x. 170. 

 Agricultural Journal, xvi. 53J. 



