FARMYARD MANURE. 7 



6. With respect to the inorganic or mineral constituents of 

 fresh dung, it will be seen that it contains all those mineral 

 matters which are found in the ashes of all our cultivated 

 plants. 



7. Comparing the composition of the soluble inorganic matters 

 with that presented by the insoluble, no essential qualitative dif- 

 ference is perceived between both, for the same constituents 

 which occur in the soluble ash are found also in the insoluble 

 ash. But there exists a striking difference in the quantitative 

 composition of the soluble and the insoluble mineral matters of 

 fresh dung. 



8. The principal constituent of the soluble ash of fresh dung, 

 so far as quantity is concerned, is potash ; 100 parts of soluble 

 ash, it will be seen, contain no less than 37'26 parts of real 

 potash, or a quantity which is equivalent to 54*7 of pure car- 

 bonate of potash. The analysis of the soluble portion of ash 

 of fresh dung gave only 14 per cent, of carbonic acid, in- 

 cluding the loss in analysis; and as 37*26 of potash take up 

 17*5 of carbonic acid in becoming carbonate of potash, and 

 moreover much of the soluble lime existed in the water-solution 

 as bicarbonate of lime, it is evident that a considerable quantity 

 of potash is united with silicic acid in the soluble ash. The 

 large percentage of soluble silica confirms this view ; fresh farm- 

 yard manure thus contains much soluble silicate of potash. 



9. The large amount of soluble silica, both in the soluble and 

 in the insoluble ash, is deserving notice. In the soluble ash 

 this silica is united principally with potash, and probably also 

 with some soda ; in the insoluble ash it is combined chiefly with 

 lime, or exists in a finely divided state, in which it is readily 

 soluble in dilute caustic potash. 



10. The most prominent constituent of the soluble ash of fresh 

 dung is silicate of potash. 



11. The most prominent constituent of the insoluble ash is 

 lime. 



12. It is particularly worthy of notice that the soluble ash of 

 even perfectly fresh dung contains a very high percentage of phos- 

 phate of lime. 



The proportion of phosphate of lime in the soluble portion of 

 ash was in fact found to amount to no less than 19 J per cent, of 

 the whole soluble ash, whilst the percentage of phosphate of lime 

 in the insoluble ash was found to be only 9^. 



I must confess that I was not prepared to find so large an 

 amount of a compound which is generally considered insoluble 

 in water, and for this reason is not enumerated in the published 

 analyses of farmyard manure amongst the soluble constituents of 

 dung. Repealed experiments, however, executed, with all care 

 to avoid any possible source of error, have shown me that water 



