202 CULTIVATION. 



plow and for a considerable distance sideways tow- 

 ard the surface. If the land is too wet, this motion 

 will be injurious rather than beneficial, but if it is 

 dry enough to crumble, it will be very much loosened. 

 If we hold in the hand a ball of dry clay, and press 

 it hard enough to produce the least motion among 

 its particles, the whole mass becomes pulverized. 

 On the same principle, the sub-soil plow renders the 

 compact lower soil sufficiently fine for the entrance 

 of roots. 



Notwithstanding its great benefits on land, which 

 is sufficiently dry, sub-soiling cannot be recommended 

 for wet lands ; for, in such case, the rains of a single 

 season would often be sufficient to entirely overcome 

 its effects by packing the sub-soil down to its former 

 hardness. 



On lands not overcharged with water, it is produc- 

 tive of the best results, it being often sufficient to 

 turn the balance between a gaining and a losing 

 business in farming. 



It increases nearly every effect of under-draining ; 

 especially does it overcome drought, by loosening 

 the soil, and admitting air to circulate among the 

 particles of the sub-soil, and deposit its moisture, on 

 the principle described in the chapter on under- 

 draining. 



It deepens the surface-soil, because it admits roots 

 into the sub-soil where they decay and leave carbon, 

 while the circulation of air so affects the mineral 

 parts, that they become of a fertile character. As 

 a majority of roots decay in the surface-soil, they 



