JETHKO TULLS THSOBY. 9 



vols.), was published in London in 1738 ; and contain- 

 ed, as will be seen from its title, records of experiments 

 of very much the same nature as those of Duhamel. 



Jethro TulVs Theory. 



Some reference may be made to a theory which 

 created a considerable amount of interest when it was 

 first published viz., that of Jethro Tull. The chief 

 value of Tull's contribution to the subject of agricul- 

 tural science was, that he emphasised the importance 

 of tillage operations by putting forward a theory to 

 account for the fact, universally recognised, that the 

 more thoroughly a soil was tilled, the more luxuriant 

 the crops would be. As Tull's theory had a very 

 considerable influence in stirring up interest in many 

 of the most important problems in agricultural chem- 

 istry, and as it contained in itself much, the value of 

 which we have only of late years come to understand, 

 a brief statement of this theory may not be without 

 interest. 



According to Tull the food of plants consists of the 

 particles of the soil. These particles, however, must 

 be rendered very minute before they become available 

 for the plant, which absorbs them by means of its root- 

 lets. This pulverisation of the soil goes on in nature 

 independently of the farmer, but only very slowly, and 

 the farmer has therefore to hasten it on by means of 

 tillage operations. The more efficiently these opera- 

 tions are carried on, the more abundant will the supply 



