SCIENTIFIC AGRICULTURE. 211 



marl, gypsum, chalk, and composts containing Urn?, may be 

 applied at any time. Lime, in order that it may produce its 

 full effect and most lasting benefit, should bo kept near the 

 surface. This may be done by sub-soil ploughing, by which 

 the lime is thrown up to the surface; and also by sowing deep 

 rooted crops, which will reach it after it has sunk too deep to 

 benefit others of shorter roots. The amount of lime in the 

 soil gradually diminishes from several causes, when it is not 

 occasionally replenished : it is removed to a small extent with 

 the annual harvests, and by assuming new forms by chemical 

 action ; a portion is also carried away in solution with the 

 water which falls by rain and filters through both the surface 

 and subsoil. 



The beneficial effects of lime, although more permanent, are 

 not felt as soon as those of some other mineral manures : it is 

 of little service on soils deficient in organic matter. The length 

 of time which lime shows its effects upon the crops and soil, is, 

 according to circumstances, from ten to thirty years. Its use 

 is sometimes attended by unfavorable results when not judi- 

 ciously used: light, loose soils are rendered too loose; and the 

 growth of certain noxious weeds favored by its-presence : an 

 ov(r-doso destroys too much organic matter, hardens certain 

 soils, ^id injures the spongioles of young plants. It is said to 

 operate injuriously upon flax, by causing tenderness of its cor- 

 tical fibre. 



These remarks on the use of lime as a manure, are conden- 

 sed from Johnston, who has given perhaps the best treatise on 

 lime extant. As the subject is both important and interesting, 

 it may be well to recapitulate briefly. 

 Recapitulation. 



1. Lime increases the fertility of soils deficient in this element. 



2. It causes the soil to produce grain which yields more flour 

 and less bran, and improves the quality of all other crops. 



