Farmyard Manure. 143 



For better comparison's sake, T will give the composition of 

 the drainings before and after passing through soil, and tlien 

 make a few additional remarks which are suggested by such a 

 comparison. 



Composition of Braininrjs from Botten Dung. 



1 imperial gallou contains— 



Before After 



Filtration Filtration 



through Soil. 



Ammonia (in the form of ammoniacal sails) 19'6S G-91 



Organic matters 134'05 118'50 



Silica -75 2-38 



Phosphates of lime and iron 7*90 1"54: 



Carbonate of lime 17*46 79*72 



Sulphate of lime 2-18 7*92 



Carbonate of masnesia 12"83 6"17 



Chloride of sodium 22*85 18*90 



„ potassium 35*25 20*44: 



Carbonate of potash 85*27 4*29 



iJO' 



38*22 272*77 



It will be observed that this liquid, in passing through the 

 soil, has undergone a striking change. Leaving unnoticed 

 several minor alterations in the composition of the original 

 liquid, I would direct special attention to the very small 

 proportion of carbonate of potash left in the drainings after 

 contact with this soil. It will be seen that, out of 85 grains of 

 potash contained in the original liquid, no less than 81 grains 

 have been retained by the soil. This is a result of the greatest 

 importance, inasmuch as it shows that the soil possesses, in a 

 remarkable degree, the power of removing from highly-mixed 

 manuring substances not only ammonia from ammoniacal salts, 

 but also the no less important soluble potash compounds. 

 According to this result, 1000 grains of soil absorb no less than 

 2*313 grains of carbonate of potash. But, in addition to car- 

 bonate of potash, a considerable quantity of chloride of potas- 

 sium is retained in this soil by passing the washings from rotten 

 dung through it : for it will be observed that nearly 9 grains of 

 this salt, or, in exact numbers, 8*81, were retained in the soil. 

 The avidity of the soil for soluble salts of potash is the more 

 remarkable, as it offers a striking contrast to the apparent indif- 

 ference of this soil to absorb soda from its soluble combinations ; 

 for it will be seen that the liquid, after filtration through the soil, 

 contains only about 4 grains less of common salt in the gallon 

 than before filtration. 



In a purely chemical point of view, soda salts are closely 

 allied to salts of potash, and yet there is a marked difference 

 observable in the power of this soil, at least, to absorb the one 

 or the other alkali. 



