466 NIGHT SOIL READILY :. ECOMPOSES — ITS COMPOSITION. 



§ 12. Of solid animal manures— night soil, the dung- of the cov^ ife 

 horse, the sheep, and the pig. 



1°. Night soil is in general an exceedingly rich and valuable ma- 

 nure, but its disagreeable odour has in most countries rendered its 

 use unpopular among practical men. This unpleasant smell may be 

 in a great measure removed by mixing it with powdered charcoal or 

 with half-charred peat,— a method which is adopted in the manufac- 

 ture of certain artificial manures. Q,uick-lime is in some places em- 

 ployed for the same purpose, but though the smell is thus got rid of, 

 a large portion of the volatile ammonia produced during the decom- 

 position of the manure is at the same time driven off by the lime. 



In general, night soil contains about three-fourths of its weight of 

 water, and when exposed to the air undergoes a very rapid decompo- 

 sition, gives off much volatile matter — consisting of ammonia, of car- 

 bonic acid, and of sulphuretted and phosphuretted hydrogen gases — 

 and finally loses its smell. In the neighborhood of many large cities, the 

 collected night soil is allowed thus naturally to ferment and lose its smell, 

 and is then^dried and sold for manure, under the name of poudrette. 



But by this fermentation a very large pro'portion of valuable matter 

 is permitted to escape into the air. To retain this, gypsum or dilute 

 sulphuric acid may be added to the night soil, but the more economi- 

 cal and generally practicable method is to mix it with earth rich in ve- 

 getable matter, with partially dried peat, with saw-dust, or with some 

 other readily accessible absorbent substance. In this way a rich and 

 fertilizing compost will be obtained, which will have little smell, and 

 yet will retain most of the virtues of the original manure. 



In China the fresh night soil is mixed up with clay and formed into 

 cakes, which when dried are sold under the name of Taffo, and form 

 an extensive article of commerce in the neighborhood of the larger cities. 



The composition of night soil, and consequently its value as a ma- 

 nure, varies with the food, and with many other circumstances (p. 470). 

 The excrements of a healthy man were found by Berzelius to consist of: 



Water 733 I Mucilage, fit, and other ani- 



Albumen 9 | mal matters 167 



Bile 9 j Undecomposed food 70 



Sahne matter 12 | TOOO 



Of the excrement when freed from water 1000 parts left 132 of ash.viz. 



Carbonate of soda 8 1 Phosphate of lime and magne- 



Sulphate of soda, with a little [ sia, and a trace of gypsum . . 100 



sulphate of potash, and phos- Silica 16 



phate of soda 8 | 132 



2°. Cow dung forms by for the largest proportion of the animal ma- 

 nure which in modern agriculture is at the disposal of the practical 

 farmer. It ferments more slowly than night soil, or than the dung of 

 the horse and the sheep. In fermenting it does not heat much, and it 

 gives off Httle of an unpleasant or ammoniacal odour. Hence it acts 

 more slowly, though for a longer period, when applied to the soil. 



The slowness of the fermentation arises chiefly from the smaller 

 quantity of nitrogen, or of substances containing nitrogen, which are 

 present in cow dung, but in part also from the food swallowed by the 

 cow being less perfectly masticated than that of man or of the horse. It 



