MANURES. 81 



soil. I have purposely used a large amount of liquid in compari- 

 son with that of soil. If, under such conditions, the soil is capable 

 of retaining two-thirds of the whole amount of ammonia present in 

 a liquid like the one examined, it is not too much to expect that 

 no ammonia whatever will be lost in practice by carting manure 

 on the fields in autumn, and spreading it at once. The quantity of 

 soluble ammoniacal matters in a heavy dressing of the best dung 

 does not amount to many pounds, and such a quantity, in relation 

 to the weight of the soil ready to take up ammonia from the ma- 

 nure, is so insignificant that the most scrupulous may rest satisfied 

 that in a soil containing even a small proportion of clay no ammo- 

 nia will be lost by dressing the fields in autumn. 



Other no less important changes than those referring to the ab- 

 sorption of ammonia will strike the reader to have taken place in 

 these drainings left in contact with the soil. For better compari- 

 son sake, I will give the composition of the drainings before and 

 after passing through the soil, and then make a few additional re- 

 marks which are suggested by such a comparison. 



Composition of Drainings from Eotten Dung. 

 One imperial gallon contains : 



Before filtration After filtration, 

 through soil. 



Ammonia (in the form of ammoniacal salts), 19.68 6.91 



Organic matter, 134.05 118.50 



Silica, .^5 2.38 



Phosphate of lime and iron, t.90 1.54 



Carbonate of lime, IY.46 19.12 



Sulphate of lime, 2.18 ^.92 



Carbonate of magnesia, 12.83 6. It 



Chloride of sodium, 22.85 18.90 



Chloride of potassium, 35.25 26.44 



Carbonate of potash, 85.21 4.29 



338.22 272.17 



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

 has undergone a striking change. Leaving unnoticed several mi- 

 nor 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 draining after contact with this soil. It will 

 be seen that, out of eighty-five grains of potash contained in the 

 6 



