194 A PRACTICAL TREATISE 



a gaseous exhalation a very short time after it is put together; 

 and the quantity thus thrown off is regulated by the state of 

 the atmosphere. But this exhalation does not consist of the 

 valuable gases; it is a mere evaporation of the water contained 

 in the dung. The same hot haze may be seen flickering over 

 a fallow field in a sunny day in summer. Nobody could with 

 truth assert, that this haze arises from the disengagement of 

 the gases in the dung which had previously been inserted into 

 the soil, when it is clearly nothing more than the evaporation 

 of the moisture in the soil. To say, therefore, the first stage 

 of decomposition in a dunghill throws off^ "the most valuable 

 and the most efficient" parts of the dung, is just to say the 

 vapour of water is the most valuable part of dung. 



*It is true, were the fermentation continued after all the 

 water in the dung was evaporated, a considerable increase of 

 temperature would ensue; and when the texture of the fibrous 

 portions of the manure began to decompose, there would be an 

 evolution of valuable gases. Direct experiment has proved 

 the escape of gases from a heap of dung which has been long 

 fermenting. But what harm accrues to the dung as a manure 

 from the escape of these gases'? None whatever. We are 

 told these gases constitute the food of plants, and if they are 

 permitted to be dissipated by decomposition, the quantity of 

 nourishment in the heap of manure will of course be so much 

 diminished ; that if the bulk of the dungheap be diminished 

 one-half or one-third by excessive fermentation, the quantity 

 of nourishment to the crops will be diminished in a greater 

 ratio. These cautions have long been whispered in the ears 

 of practical men, but they have listened to the advice w4th a 

 provoking indifl^erence. Like ducklings w^hen they first take 

 the water, they have continued to disregard every remon- 

 strance of their foster brethren against injurious practices, 

 raising and devouring their food, and enjoying themselves 

 with the greatest complacency in their vocation. It is true, 

 and we must admit it, that some of the gases constitute the 

 food of plants, but it does not follow that plants would receive 

 them as food directly as they are disengaged from a ferment- 

 ing and heated mass ; nay, it is probable they would rather 

 reject the food that would injure them. But as plants are not 

 endowed with locomotive powers, they cannot avoid the food 

 which is directly presented to them; they will therefore be 

 obliged to partake of it even in an injurious state, and in thus 

 taking it they die. Accordingly, we invariably fiind that 



