Successive Corn-crops. 19 



and where the agriculturist is free to follow a 

 rational system of farming. The four-course 

 system of alternate corn and green crops — 

 wheat, turnips, barley, clover — had two great 

 advantages, first, by alternating restorative and 

 cleansing crops with corn ; and second, by 

 regular distribution of labour throughout the 

 year. The introduction of guano, nitrate of 

 soda, and other ammoniacal and phosphatic 

 manures, has now rendered the farmer compara- 

 tively independent of this alternate system of 

 cropping. As the supply of nitrate is believed 

 to be capable of lasting for a very long period, 

 we may reckon with considerable certainty on 

 its continuance at a moderate price. It misrht tt . 



^ •=> Use to 



become an instrument of great national value if ^^"'^^ '^^^ 



'-' mignt oe 



any unforeseen occurrence should cut off one of ofwaV""'^ 

 our main supplies of wheat, that of Russia, for 

 example. If only the twentieth part of the corn 

 land of the United Kingdom were called on to 

 bear an additional wheat-crop, the loss would be 

 at once made good, and with no perceptible 

 strain on our agricultural system. If all Europe 

 were shut against us, we should be quickly able 



