MANURES. 239 



" be converted into earth closets, and to provide for their sys- 

 ''tematic and thorough inspection." 



In concluding these remarks, it need only be stated, in general 

 terms, that whatever process is adopted for the economical saving, 

 and the proper application of night-soil as manure, its use must 

 inevitably be attended with the best results, not only on the in- 

 dividual farms to which it is applied, but as most favorably affect- 

 ing the agriculture of the whole country; and probably it will be 

 found that the use of dry earth in some form, and by means of 

 whatever appliances may be within the most convenient reach of 

 the farmer, will afford very much the most economical and satis- 

 factory solution of the problem. 



MINERAL MANURES. 



By reference to remarks in preceding chapters, concerning the 

 composition of plants and their uses in the animal economy, it 

 will be remembered that certain portions of them, which consti- 

 tute the ash left after the burning of any vegetable matter, are of 

 a mineral character and origin ; that is to say, they exist in a 

 state of nature, always and only as constituents of the soil or of 

 the rocks from which the soil is originally formed ; — and while 

 they are absolutely necessary to the growth of plants, they can 

 be taken up only by the roots from the soil ; for they never exist, 

 except as dust, in the air. 



While these mineral or earthy constituents constitute but a 

 very small proportion of the plant, and of the animal which gets 

 the substance of its body from the digestion of plants eaten, they 

 are absolutely indispensable to all organic growth ; and their im- 

 portance in agriculture is by no means to be measured by the 

 extent to which they are used. The amount of potash required 

 in the formation of the integral parts of a blade of wheat, is so 

 small as to escape any but the most careful scrutiny. Yet it is 

 absolutely impossible to produce a blade of wheat without furnish- 

 ing the necessary supply of this apparently insignificant element. 

 The same is true, in a greater or less degree, of all the mineral 

 parts of plant-food. 

 16 



