1 22 LESSONS IN CHEMISTRY. 



which they contain are rendered soluble. The first shower 

 of rain, therefore, which pours upon the heap more water 

 than it can soak up, flows away, carrying with it some of 

 the phosphoric acid, sulphuric acid, potash, and other valuable 

 ingredients, which had given fertility to yom- fields. These 

 substances, with some of the ammonia, which is exceedmgly 

 soluble in water (16), are swept into the drains.* 



Thus, though the manure heap is formed of materials rich 

 in all the substances which enter into the composition of our 

 crops, as usually managed, it must, when applied to the land, 

 be deficient in much of its original fertilizing power. 



180. Farm-yard manure usually contains about 70 per 

 cent of water, 20 per cent of organic matters, and 10 per 

 cent of earthy and saline matters ; and it is calculated that, 

 on the average, 10 tons of it convey to the soil about 1 cwt. 

 of ammonia and 781bs. of phosphoric acid, and the same 

 amount of potash. From the great variety, however, of 

 materials composing it, every sample of this manure will vary 

 widely in composition, and an account of the analyses of it 

 which have been published, would convey but little infor- 

 mation to the farmer. It will be of greater consequence to 

 consider how the loss of the volatile matters which are set 

 free during fermentation, and also of the inorganic matters 

 which are so liable to be washed out by eur frequent showers, 

 may be most efifectually prevented. 



In wet weather, you will observe on every part of the 

 countiy a black stream oozing from the farm-yards, and 



* The drainings of farm-yard dung have been analyzed, and found 

 to be exceedingly rich ui fertilizing matters. The following is the 

 composition of an imperial gallon of the liquid, examined in the Labo- 

 ratory of the Agricultural Chemistry Association of Scotland : — 



Ammonia 21.6 grs. 



Organic matter 77.6 



Inorganic matter, or ash .... 618.4 



617.5 grs. 

 The inorganic matter contained in the liquid consisted of 



Alkaline Salts 420.4 grs. 



Phosphates of Lime and Magnesia 44.5 



Carbonate of Lime 31.1 



Carbonate of Magnesia, and loss 3.4 



Silica, and a little Alumina 19.0 



518.4 grs. 



