AND AGRICULTURE. 



59 



Tig. 18. 



foundation. It is always better mixed into a 

 compost with other manures than used alone. 



Cow dung is colder, and less easily decom- 

 posed, because, by the large quantity of urine 

 voided by the cow, most of the excrementitious 

 salts are carried away. This defect may be rem- 

 edied by the addition of wood-ashes, or quick- 

 lime, well turned into the heap, whereby the 

 process of decomposition is greatly hastened, and 

 the manure much improved. 



The mixed dung of animals dif- 

 fers from the food they consume, 

 in containing less carbon and 

 more nitrogen than the food eaten. 

 The carbon is thrown off by the 

 lungs in the act of breathing, in 

 the form of carbonic acid gas. A 

 man throws off from his lungs 

 about half a pound of carbon daily ; and a horse 

 or a cow, eight or ten times as much. You may 

 see the carbonic acid, as it is thus thrown off by 



Questions. How is pig-dung best used ? Why is cow 

 dung less valuable as a manure ? How may it be much 

 improved ? Wherein does the dung of animals differ from 

 their food ? What becomes of the carbon ? How much carbon 

 does a man throw off daily ? How much a horse or cow ? 



