142 ON THE rniNciPLES of 



On fields which are richly provided with all the other 

 mineral ing-redients, with the exception of gypsum, the latter 

 is applied with the greatest success. But if gypsum is pre- 

 sent in the soil, the same eifects are produced hy ashes and 

 lime, as is the case in Flanders. On fields in which phos- 

 phate of lime is wanting, bone ashes increase the produce of 

 grain, clover, or grass ; and on argillaceous soil, lime pro- 

 duces a decided improvement. All these substances act 

 only on those fields which are defective in them, and if the 

 other elements of the soils are present : the latter cause the 

 former to come into action, and rice versa. The farmers 

 who thought that by using lime, gypsum, bone earth, ifcc, 

 they might dispense with animal manure, very soon ob- 

 served that their fields deteriorated. They observed that 

 after a third or fourth successive manuring with those simple 

 substances the produce decreased ; that, as is the common 

 expression, the soil became tired of the manure, that at last 

 the field scarcely produced the seed. 



It is evident from this, what is the action of the mineral 

 elements in the soil. If, in fact, in the first years, the pro- 

 duce of the soil had increased by the application of bone- 

 ashes, or by a single element of the manure — if this increase 

 was dependent on the amount in the soil of the other mineral 

 elements, a certain quantity of those was annually taken up 

 by the plants and removed in the harvest ; and a time must 

 at last arrive in which it is exhausted by the repeated re- 

 moval ; the soil must become barren, because, of all removed 

 elements, only one or the other, and not all of them in a right 

 j)ro]iortion, have been restored. 



The right proportion of the supply is, however, the only 

 true scientific basis of agriculture. 



If we subject the fluid and solid excrements of men and 

 animals to an exact analysis, and compare the elements of 

 them according to their weight, some constant relations be- 

 tween these elements impress themselves upon the mind, the 

 knowledge of which is of some importance. 



If the excrements of an animal are collected with some 

 care, and left to themselves for some days, their nitrogen 

 appears to have been converted, more or less perfectly, into 

 ammonia. In the fluid excrements, in the urine, the salts 

 of the food, which are soluble in water, are found in the 

 form of alkaline carbonates, or of sulphates, phosphates, and 

 other salts, with alkaline bases. In the solid excrements or 



