On Paring and Burning. 5 



growth of plants, for which reason it is deemed most important 

 by those who hold this view to preserve them as much as pos- 

 sible in the soil. 



It cannot be denied that organic matters are desirable in most 

 soils. The fact that well-cultivated and productive soils (like 

 many rich wheat loams, and most garden soils) invariably con- 

 tain much organic matter, has led many agriculturists to connect 

 intimately the larger or smaller proportion of organic matter in 

 different soils with their relative productiveness. Not many 

 years ago it was customary with most agricultural writers to 

 estimate the relative state of fertility of different soils by deter- 

 mining the amount of humus, i. e. decomposed organic matters 

 in each. This, however, is clearly contrary to reason and well- 

 ascertained facts ; for there are spils which, like peaty lands, or 

 the soil of poor pastures, contain a very high percentage of 

 organic matter, and yet are quite sterile. On the other hand, 

 there are soils which, like many very fertile clays, hardly con- 

 tain any humus, and yet are highly productive. These incon- 

 sistencies have compelled the adherents of the humus theory 

 to assume a number of such terms as dead, inert matter, sweet 

 and sour humus terms which, in the sense in which they are N 

 generally used even now are meaningless, and which for this 

 reason might with much benefit be subjected to the process of 

 burning. 



The humus theory has retarded rather than promoted agricul- 

 tural improvements. Happily it may be regarded at present as 

 fully exploded. Had Liebig done nothing else for agriculture 

 but to give the coup de grace to the humus theory, by means of 

 his irresistible argumentative writings, the agricultural com- 

 munity would still be highly indebted to the great German 

 chemist ; for as long as this theory found favour with practical 

 men, much to their disadvantage, the importance of the mineral 

 constituents, so necessary for every description of agricultural 

 produce, was altogether overlooked. It was reserved for Liebig 

 to give general recognition to the fact, that the mineral matters 

 which enter into the composition of plants are not merely acci- 

 dental, but essential, constituents, without which plants cannot 

 live ; and to point out in a clear and convincing manner the 

 necessity of the presence in the soil of those mineral matters 

 which are found in the ashes of the plants we intend to cultivate. 

 The influence of Baron Liebig's writings on this subject upon 

 agricultural improvements can hardly be over-estimated. It is 

 not saying too much that Liebig' s writings have given a new 

 impulse to agricultural pursuits, and created a new branch of 

 industry, viz. the manufacture of artificial manures. Though 

 unsuccessful in the first attempt to manufacture efficient artificial 

 manures, Liebig has nevertheless opened the way to the manu- 

 facture and general application of artificial manures. 



