52 OPEN AIR GKAPE CULTURE. 



these means the excrement! tious matters discharged 

 by plants, as well as other noxious bodies are washed 

 out of the subsoil or decomposed by contact with the 

 air which penetrates along with the water. In the 

 case of oxide of iron it is probable that a very 

 beneficial effect results from its conversion from the 

 protoxide to the peroxide by means of this influence. 



But a change in the chemical constitution and 

 action of the soil is not the only effect of this opera 

 tion ; a no less marked alteration is produced in its 

 mechanical character heavy lands being rendered 

 light, porous and permeable to the roots of tender 

 plants. 



It is unnecessary here to give minute directions for 

 performing such a well-known operation, so we shall 

 merely refer our readers to some of the numerous 

 treatises on that subject. An excellent article on the 

 theory and practice of draining will be found in the 

 &quot; Rural Annual &quot; for 1859 published at the office of the 

 &quot; Genesee Farmer,&quot; Rochester, N. Y. 



&quot;We may state, however, that in laying drains for a 

 vineyard, it should be borne in mind that after the 

 vines are planted it will be almost impossible to get 

 at the drains in case of accident, without serious 

 detriment to the plants. It will, therefore, be well to 

 construct them in the most substantial manner and 

 also to arrange them so that they will not lie imme- 



