ROTATION OF CROPS. 73 



It was long since discovered* that the soil, when 

 left to itself, was never either exhausted, or tired, 

 or idle ; but that, however stripped or denuded by 

 man and the animals he employs, it hastens to cover 

 itself with a variety of plants, of different and even 

 opposite characters ; that some of these have a ten- 

 dency to render the earth more compact, while 

 others have the effect of opening and dividing it ; 

 that some, from peculiar structure of roots, stems, 

 and leaves, derive most of their nourishment from 

 the earth ; while others, differently formed, draw it 

 principally from the atmosphere ; and, lastly, that 

 in these voluntary products there is a continual 

 and nearly regular succession of plants differently 

 organized. These observations, carefully made and 

 no longer doubted, and others leading to the same 

 or similar conclusions, first suggested the useful- 

 ness of taking nature as our guide, and of conform- 

 ing our artificial crops to the rules which obviously 

 governed her spontaneous productions. The effect 

 was such as was expected, and for more than half 

 a century the rotation system has formed the true 

 test of agricultural improvement in every variety 

 of soil and climate. Whenever it has been adopt- 

 ed, the art is found in a state of prosperous progres- 

 sion; whenever neglected or rejected, it is either 

 stationary or retrogade. Yet, in the face of a fact, 

 carrying with it such conclusive evidence, the bulk 

 of agriculturists continue to resist this cheap and 

 obvious means of improvement, and pertinaciously 

 adhere to a system (that of fallows) which con- 

 demns to annual sterility one fourth part of the 

 earth ; and which prefers four months' unproductive 

 labour to abundant harvests and nutritious crops ! 



* Virgil, who was a philosopher as well as a poet, appears to 

 have thoroughly understood this branch of natural history : 

 " mutatis quiescunt feetibus arva." The true repose of the earth 

 is in a change of its productions. 



