OTHER SALTS IN SOILS. 209 



supposed manner of the waste being produced. But there is an- 

 other connected and similar subject which deserves notice. 



The salts of lime are not all the salts, nor the only soluble mat- 

 ters, usually present in soils. The inorganic parts of plants, 

 forming their ashes, after their being burnt, consist mostly of 

 various salts, not only of lime, but also of other bases, as magnesia, 

 potash, soda, &c. These salts, of course, were drawn by the plants 

 from the soils on which they grew. From their being universally 

 present in plants (so far as known), modern chemists have inferred 

 that all these various salts are essential to the health, if not to the 

 existence of the plants, and, of course, essential to the productive- 

 ness of the soil for these plants. But most or all of these salts, of 

 magnesia, potash, soda, &c., are soluble in water, and some very 

 easily soluble. If, then, as Prof. Johnston argues as to lime, water 

 necessarily dissolves and removes whatever soluble salt or earth is 

 existing in soils, I would ask why have not all these other soluble 

 matters been removed from all soils ? These are present usually 

 in much smaller proportions than lime or its salts, and therefore 

 could be more easily dissolved and removed. That no such com- 

 plete loss of these other salts has been produced in any soil, so far 

 as known, is another sufficient reason for inferring that neither is 

 lime, nor its more soluble salts, likely to be taken away from the 

 soil, when acting usefully as fertilizing matters, by the solvent 

 action of water. This view of the case is still stronger in another 

 aspect. Liming in England and Scotland is usually renewed (as 

 stated above), or requires renewal, in twenty years or thereabout. 

 The farmers of Norfolk (England) also renew their heavy marlings 

 every eight years or sooner. Hence it is argued that the calcareous 

 manure is exhausted in some such limited times. But the other 

 salts, of magnesia, potash, soda, deemed by modern chemists as 

 essential to soils and to their production, are almost never replaced 

 by artificial applications, or by design, even under the highest and 

 best farming, and absolutely never (unless by rare accident) in 

 ruder culture. Hence it would seem legitimately deduced from 

 Prof. Johnston's reasoning as to the disappearance of lime, that 

 even in the highly-limed and cultivated lands of Britain, the other 

 elements of fertile soil, all deemed as essential to production as 

 lime, ought to have been exhausted long ago. On nearly all other 

 parts of the world, not only all these other substances, but also the 

 lime itself, ought to have been entirely removed, and every soil 

 rendered barren. This reduction to an absurd conclusion would 

 alone be enough to disprove the argument I oppose. 



Prof. Johnston, in his attempt to prove the transitory existence 



and operation of lime as manure, has committed an error to which 



scientific men who treat on practical agriculture are extremely 



prone. This is to suppose that matters in the soil act with and 



18* 



