292 History of the English Landed Interest. 



salts b}'' means of fermentation. " The fermenting quality of 

 Dung," lie says, " is cliiefly owing to the Salts wherewith it 

 abounds ; but a very little of this Salt applied alone to a few 

 Roots of almost any Plant will (as in my Mint Experiments it 

 is evident common Salt does) kill it." His association of all 

 kinds of salts with chloride of sodium (with a saturated solu- 

 tion of which he had contrived to destroy more than one 

 species of plant) shows how very superficial was the chemical 

 knowledge of the time. Tull did not go so far as to suggest 

 the entire exclusion of dung from the farm. Common tillage 

 alone was not sufficient, he said, for many sorts of corn, es- 

 pecially wheat. But few fields could obtain a sufficient supply 

 of this manure, save those near cities. It was, he admitted, a 

 source of warmth to plant life, though it was difficult to decide 

 whether the process of fermentation continued long enough to 

 produce on this account other than temporary benefits. In 

 the cultivation, however, of pastures and turnips, the results of 

 this author's experiments had induced him to give up the use 

 of dung entirely. 



The outcome of all such ideas as these was to lead Tull 

 to decide that the chief advantages of dung were its me- 

 chanical effects, such as heat and attrition brought about by 

 its fermentation. These were, to his mind, almost entirely 

 counteracted, partly by its being imattainable to any adequate 

 amount, partly by the various disadvantages enumerated in 

 the discussion of its use in the flower and kitchen garden. 

 The question therefore arose : " was there any equally effective 

 substitute ?" which Tull thought was answered in the affirma- 

 tive by a description of his horse-hoeing process. To break 

 and divide the seed-bed by means of tilkge was to open up to 

 the roots of the plant that inexhaustible supply of nourish- 

 ment which insufficient dung would fail in supplying. "Every 

 time," he says, " the Earth is broken by any sort of Tillage or 

 Division, there must arise some new Superficies of the broken 

 Parts which never has been open before." The small modicum 

 of truth in such reasoning militated against any immediate 

 revelation of its ultimate failure. The light soils of Norfolk 

 have long ago been so " clover sick " that it is useless for the 



