306 GUANO. 



texture materially modified by the constant treading 

 of the sheep. 



814. Guano, the residue of the putrefaction of the 

 excrement of sea-fowl, consists chiefly of various 

 salts of ammonia, inorganic compounds, and unde- 

 composed organic matters, analogous in nature to 

 horn and wool (818). The salts of ammonia dissolve 

 easily in water, and are at once absorbed by plants, 

 whilst the undecomposed organic matter, gradually 

 undergoing decomposition, continues for some time 

 to yield a regular supply of ammoiiia. In guano, 

 there exists all the chemical elements of an excellent 

 manure ; but of course it does not produce the 

 same mechanical effect on the soil which yard dung 

 does. 



815. In using guano as liquid manure, it must be 

 remembered that the solution formed by pouring 

 water over it only contains the ammonia and about 

 one quarter of the phosphates, the rest of the phos- 

 phates, and the organic matter, being almost insolu- 

 ble in water ; hence the residue is nearly as valuable 

 a manure as that which is dissolved ; and in order 

 to derive the whole bene:fit from the manure, the in- 

 soluble part must, by agitation or other means, be 

 kept suspended in the liquid whilst it is being spread 

 over the ground. 



816. Analogous in nature and value to these sub- 

 stances are dead fish, and the refuse matters left in 

 curing and preserving fish; sugar-refiners' waste, 

 which is a mixture of charcoal, blood, and the various 



