AND AGRICULTURE. 61 



sition of manures, is changed into ammonia, which 

 is a kind of air, or gas, having a very strong 

 smell. The hartshorn of the shops is only water 

 holding ammoniacal gas in solution ; and smell- 

 ing-salts owe their pungency to the ammonia 

 they contain. 



The ammonia is produced by the fermentation 

 of compost or manure heaps, and is the cause of 

 the smell perceived in stables and privies. It is 

 a very valuable agent in manures, and should be 

 kept from flying off by the addition of sulphate 

 of lime, whereby the volatile carbonate of am- 

 monia is transformed into the non-volatile sul- 

 phate of ammonia. 



You may detect the presence of ammonia by 

 dipping a feather into vinegar and holding it 

 over the dung-heap in the stable, when, if am- 

 monia is forming, it will be seen in white fumes 

 around the feather. 



Another method will enable you to see the 

 ammonia. Dip a feather into strong vinegar, 



Questions. Into what is nitrogen changed by the fer- 

 mentation of manures ? Describe ammonia. What is the 

 cause of the smell of stables and privies ? Should the an*- 

 monia be retained in the manure ? How should it be kept 

 from flying off ? How can you detect ammonia ? 



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