THE PRINCIPLES OF ENGLISH AGRICULTURE. 147 



dition, so that the full advantages of its mechanical effects 

 may be obtained. So important in fact are the mechanical 

 effects of farmyard dung that Jethro Tull, who has been 

 called the father of modern husbandry, and who flourished in 

 the last century, absolutely refused to believe that farmyard 

 dung exerted any but a mechanical effect, and in his homely 

 phraseology he said farmyard dung fed the plant in the same 

 sense that his knife and fork fed him. It divides the food 

 and prepares the food for the inception of the materials by 

 the roots, and therefore he considered that while the effects 

 of farmyard manure were undoubted, yet at the same time 

 they resembled tillage effects ; and he was led from that to the 

 conclusion that all that farmyard dung did, could be done by 

 means of repeated and constant tillage, and, what is more, he 

 did it. That was his theory, and it is a good example of how 

 it sometimes happens that men with defective theories will 

 arrive at a sound practical conclusion. Jethro Tull abandoned 

 the use of farmyard dung, tilled his ground, and produced 

 wheat year after year upon the same land without the use of 

 dung, but merely by the aid of tillage implements. 



It is rather curious, after the lapse of many years, and after 

 much light had been thrown upon the science of agriculture, 

 to find in one of his latest works that great pioneer, Baron 

 Liebig, taking up a very similar view to that of Jethro Tull, 

 not only with regard to farmyard dung, but to nitrate of 

 soda, sulphate of ammonia, and common salt. Liebig, as 

 you know, espoused the mineral theory, and according to his 

 teaching the ammonia and nitrogen of the plant were derived 

 from the atmosphere, and therefore all that was required was 

 to add the mineral plant food to the soil, and that being done 

 the plant was able to reach forth its leaves, and take its 

 nitrogen from the atmosphere. When it was clearly demon- 

 strated that the effect of nitrogenous manures were most 



potent, and exceeded very much the action of mineral manures, 



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