ITS ESSENTIAL ELEMENTS. 181 



The peculiar action, then, of the solid excrements 

 is limited to their inorganic constituents, which 

 thus restore to a soil that which is removed in the 

 form of corn, roots, or grain. When we manure 

 land with the dung of the cow or sheep, we supply 

 it with silicate of potash and some salts of phos- 

 phoric acid. In human faeces we give it the phos- 

 phates of lime and magnesia ; and in those of the 

 horse, phosphate of magnesia, and silicate of potash. 

 In the straw which has served as litter, we add a 

 further quantity of silicate of potash and phos- 

 phates ; which, if the straw be putrified, are in 

 exactly the same condition in which they were 

 before being assimilated. 



It is evident, therefore, that the soil of a field 

 will alter but little, if we collect and distribute the 

 dung carefully ; a certain portion of the phosphates, 

 however, must be lost every year, being removed 

 from the land with the corn and cattle, and this 

 portion will accumulate in the neighbourhood of 

 large towns. The loss thus suffered must be 

 compensated for in a well managed farm, and 

 this is partly done by allowing the fields to lie 

 in grass. In Germany, it is considered that for 

 every 100 acres of corn-land, there must, in 

 order to effect a profitable cultivation, be 20 acres 

 of pasture-land, which produce annually, on an 

 average, 500 Ibs. of hay. Now, assuming that the 

 ashes of the excrements of the animals fed with this 

 hay amount to 6*82 per cent,, then 341 Ibs. of the 



