THE COMPOSITION OF FERTILE AND BARKEN SOILS. 51 



" Humus " is another term for decaying organic matter ; you will 

 find it in any soil that has been in cultivation for some time. The 

 relative proportion of humus in soils varies exceedingly ; and you 

 find very fertile soils on the one hand with, comparatively speak- 

 ing, a small proportion of organic matter, and fertile soils on 

 the other hand, with a large proportion of such matter. This 

 will appear when you glance at the diagram headed " Vegetable 

 Moulds." 



We call soils containing a considerable proportion of organic 

 matter, vegetable moulds. The first on the table is a soil from 

 Holland, which has been reclaimed from the sea, and is extremely 

 fertile ; it contains a large quantity of organic matter ; but you 

 would be wrong to estimate the fertility of the soil by the abund- 

 ance of the organic matter. Other circumstances are to be taken 

 into account, for you observe the No. 6 soil contains 90 per cent, 

 of humus ; there is very little else in the soil but organic matter 

 and some sand ; it is simply a peat soil, and the very appearance 

 of a peat soil shows that the organic matter cannot ensure its fer- 

 tility indeed, in some instances, it is desirable to destroy the 

 organic matters. You will find that farmers of the old style stick 

 up for the presence of organic matters, and advocate the fertility 

 of those matters, while putting lime to them, which has the effect 

 of destroying them for it is one of the beneficial effects of lime, 

 that it does destroy organic matter when in that state most com- 

 monly known as sour humus, although it is not more sour than 

 other organic matters undergoing decomposition. It is one of the 

 actions of lime to convert sour humus into useful matter ; the 

 farmers then call it sweet. But the very terms of sweet and sour 

 show there is something wrong in their theory of the fertility of 

 humus. Assuming there is a land which is suffering from excess of 

 organic matter in a certain condition, the farmers would say 

 " Your humus is sour ; you want sweet humus ; lime neutralises 

 the acid and makes it sweet." But it is altogether a theoretical 

 speculation ; and it is astonishing to see how men, who are not 

 accustomed to the modern way of chemical and scientific re- 

 search, are led continually into theorising. There seems no man 

 so apt to theorise as the imperfectly instructed. Here we have a 

 soil (peat) with a vast proportion of organic matter, and it is 

 worth nothing until it has undergone radical improvement ; and 

 we perceive that what characterises fertile soils is not the mere 

 prevalence of one constituent, but the presence of a number of 

 substances all necessary for the life of our plants. 



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