ROTATION OP CROPS. 221 



roasting. This oil forms not only a mild cathartic, but with 

 some, is an article of food. Its separation into a limpid oil 

 for machinery and lamps, and into stearine for candles, has 

 lately much increased its valuable uses. 



CHAPTER XII. 



MISCELLANEOUS AIDS AND OBJECTS OF AGRICULTURE. 



We have thus far treated of soils and manures, the prepa- 

 ration of the ground and the ordinary cultivated field crops, as 

 fully as our limits will permit. It remains for us briefly to 

 add such incidental aids and objects of agriculture as could not 

 appropriately be embraced under either of the foregoing heads. 



ROTATION OF CROPS, ITS USES AND EFFECTS. 



The practice of rotation of crops is an agricultural improve- 

 ment of very modern date. It is first mentioned in Dickson's 

 Treatise on Agriculture, published in Edinburgh, in 1777. 

 Rotation has for more than a century been partially prac- 

 tised in Flanders and perhaps in some other highly cultivated 

 countries, and it was afterwards introduced and imperfectly 

 carried out on a limited scale in the Norfolk district in Great 

 Britain ; but its general introduction did not take place till the 

 beginning of the present century. The system of rotation is 

 one of the first and most important principles of general hus- 

 bandry, and it cannot be omitted without manifest disadvan- 

 tage and loss. The place of rotation was formerly supplied 

 by naked faUoics. This practice consists, as we have before 

 shown, in giving the soil an occasional or periodical rest, in 

 which no crop is taken off, and the soil is allowed to produce 

 just what it pleases or nothing at all, for one or more years, 

 when it is refreshed and invigorated for the production of its 



