314 AMMONIA AND NITEIC ACID. 



observation, and experience, more perhaps than in any 

 other business. For the rational agriculturist must not 

 merely know all the facts with which the illiterate peas- 

 ant is acquainted, but he must also be able to appre- 

 ciate them at their proper value ; he must know the 

 reason of all his proceedings, and what effect they may 

 have upon his land. He must be able to interpret what 

 his field tells him in the phenomena which he observes 

 in practice ; in a word, he must be a thorough man, 

 and not a half-and-half creature who knows no more 

 about his actions than a tom-cat, with just skill enough 

 to catch gold fish in a basin of water.* 



* If we compare the theoretical views expressed in the works of con- 

 fessedly good practical farmers with the system of husbandry which they 

 have found by their own experience to be the best, we observe the most 

 irreconcilable contradictions between the two. 



Walz ('Communications 'from Hohenheim,' No. 3, 1857) disputes both 

 these propositions, viz. : 



4 That the removal of the mineral constituents in the crops, without 

 compensation, produces sooner or later lasting unfruitfulness as a conse- 

 quence.' 



' That if a soil is to maintain its fertility continuously, the removed 

 mineral constituents must, sooner or later, be returned to it, i.e. the com- 

 position of the soil must be restored.' 



And gives as his opinion that both these propositions are at present appli- 

 cable only to soils of the worst kind, which needed a supply of mineral 

 matters from the very beginning. 



Now, if we turn to the ' Application of his theory to practice ' (page 

 117), we would naturally suppose that he would never trouble himself 

 about any compensation ; but it soon appears that he is far from believing 

 in the truth of his own doctrines. He lays the proper stress upon the 

 restoration of potash, lime, magnesia, phosphoric acid, gypsum, guano, 

 bone-earth, marl, and farm-yard manure; and lays down the following 

 rule : ' That the farmer, to keep his ground in uniformly increasing fer- 

 tility, must not remove more in his crops than the products of the atmos- 

 phere and the assimilable mineral substances added annually to the soil 

 by the action of the weather.' He says further : ' If the farmer were to 

 confine his business entirely, e.g. to the manufacture of bee r, spirit, sugar, 

 starch-meal, dextrine, vinegar, &c., and the sale of animal products merely 

 to butter, using up the skimmed milk ; if for his dairy he were to buy none 

 but full-grown cows and not breed them himself, thus endeavouring to 

 keep the phosphates upon his farm, then he would not only preserve con- 

 tinually the mineral substances in his store of manure, but he would also 

 increase them by the yearly process of disintegration, unless he preferred 

 to alienate the latter in his produce ' (s. 142). 



Hence the point of his practical teaching, in direct opposition to his 



