194 SCIENTIFIC AGRICULTURE. 



same purpose ; but, although it destroys the odor, it dissipates 

 at the same time a large portion of its ammonia. During the 

 decomposition of night soil, an evolution of carbonic acid, 

 ammonia, sulphuretted and phosphuretted hydrogen takes 

 place. After the escape of these gases, the odor ceases, and 

 the remainder, when dried, constitutes what is sold in large 

 cities under the name of poudrette. The odor of recent night 

 soil may be destroyed, and the volatile elements retained, by 

 adding to it gypsum or dilute sulphuric acid. This manure is 

 used in the form of compost, and as a top dressing in the form 

 of poudrette. 



The excrements of horned cattle are more valuable and 

 enduring in their operation than those of the horse and sheep. 

 It ferments more slowly on account of its smaller quantity of 

 nitrogen; hence it retains its virtue longer, and produces a 

 more lasting effect on the soil. It is colder in its nature than 

 that of the horse, which is owing partly to the amount of water 

 it contains, and partly to its peculiar constitution. 



The excrements of the horse abound more in nitrogen com- 

 pounds than those of cattle. Even where both are fed upon 

 the same food, those of the horse are more valuable than those 

 of the cow. It begins to heat and ferment in a short time, and 

 in two or three weeks, according to Johnston, loses nearly half 

 its original weight. On account of this rapid fermentation and 

 the consequent loss of volatile matters, it should be mixed as 

 soon as possible with charcoal, peat, sawdust, or earth rich in 

 vegetable matters, or be sprinkled with gypsum or dilute 

 sulphuric acid. For the same reason, this kind of manure 

 ought, contrary to popular opinion, to be spread upon and 

 ploughed into the soil before any signs of fermentation take 

 place ; unless it is mixed with some other matters to form com- 

 posts. Erom its tendency to ferment and develop heat, it is 

 . admirably adapted to enter into all composts. An additional 



