HOW PRACTICE SUPPORTS THEORY 243 



more so, from the feeding of the Continuous Cropping 

 ration than from the ordinary one. 



PERPETUAL MOTION — G. B. S. 



In fact, there is one point in connection with this 

 very matter of the greatest scientific and practical 

 interest. It is a point which serves to demonstrate 

 what a small amount of attention has been devoted 

 to the question of agricultural economics, or the ap- 

 plication of scientific findings to the practice of agri- 

 culture. 



The cost of the production of giant rape is not more 

 than 3s. 6d. per ton, but the manurial value of a ton 

 of giant rape — according to the admirable table com- 

 piled by Professor Crowther, of Leeds University — is 

 4s. 3d. per ton, that is, assuming that the rape is fed 

 indoors, with the further assumption that half of the 

 nitrogen and a quarter of the phosphoric acid are lost 

 in storing. 



If eaten on the land, when there would be no loss 

 of the nature indicated, the manurial value of giant 

 rape is 6s. 3d. per ton. In other words, the cost of the 

 production of giant rape (the same is true of other 

 types of winter green) is less than the manurial value 

 of the crop when consumed. 



When this fact was mentioned to Mr. George Ber- 

 nard Shaw, who has several times inspected the 

 writer's work, he referred to Continuous Cropping as 

 "going one better than perpetual motion." 



On the other hand, the manurial value of a ton of 

 roots, assuming that they are consumed indoors, is, 

 in the case of turnips, 2s. Td., swedes, 3s. 8d., man- 

 gels, 3s. 5d. per ton, whilst the manurial value of a 

 ton of meadow hay is 16s. 4d., and of a ton of oat and 

 cereal hav <£! Is. 8d> 



