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When straw is made to ferment, it becomes a more manage- 

 able manure ; but there is likewise, in the whole, a great loss of 

 nutritive matter. More manure is, perhaps, supplied for a single 

 crop, but the land is less improved than it would be supposing 

 the whole vegetable matter were finely divided and mixed with 

 the soil. 



The dung of birds that feed on animal food, such as sea-birds, 

 is considered the most powerful amongst the excrementitious solid 

 substances used as manure. The guano, which is used to a great 

 extent in South America, being the manure that fertilizes the 

 sterile plains of Peru, is a production of this kind. It exists 

 abundantly on the small rocky islands on the coasts, whither sea- 

 fowl resort at certain seasons, and being gathered, forms an arti- 

 cle of commerce. 



Night-soil is a well known and powerful manure, and very 

 liable to decompose. It differs in composition, but always abounds 

 in substances composed of carbon, hydrogen, azote, and oxygen. 

 From the analysis of Berzelius, it appears that a part of it is 

 always soluble in water, and in whatever state it is used, whe- 

 ther recent or fermented, it supplies abundance of food to plants. 



The disagreeable smell of night-soil may be destroyed by mix- 

 ing it with quicklime, and if exposed to the atmosphere in thin 

 layers, strewed over with quicklime in fine weather, it speedily 

 dries, is easily pulverised, and in this state may be used in the 

 same manner as rape cake, and delivered into the furrow of the 

 seed. The Chinese, who greatly esteem this mixture, mix it with 

 one-third of its weight of fat marl, make it into cakes, and dry 

 it in the sun. These cakes have no disagreeable smell, and form 

 a common article of commerce in that populous empire. We 

 shall hereafter describe the manner in which this and other 

 "fertilizers" are prepared for sale in this country. 



Pigeons' dung comes next in order as to fertilizing power. By 

 digesting 100 grains in hot water for several hours, it will yield 

 twenty-three grains of soluble matter ; and this affords abundance 

 of carbonate of ammonia by distillation, leaving carbonaceous mat- 

 ter, saline matter, and carbonate of lime, as a residuum. Pigeons ' 

 dung when moist, readily ferments, but after fermentation con- 

 tains less soluble matter than before, as when, in that state, 



