48 THE SOIL OF THE FAEM. 



Clay- Burning. — Stiff clays are often surface-burned, in 

 the manner described above, with the object of amchorat- 

 ing their texture and rendering them more workable. 

 The fertility of the soil is greatly increased at the same 

 time, especially in the case of calcareous clajs. 



Cobbett recommends not to burn the land which is to 

 be cultivated, but other earth for the pur2')0se of getting 

 ashes to be brought on the land ; and he advocates burn- 

 ing within v/alls of turf or earth, instead of in heaps 

 above-ground. As he points out, the princijilc of clay- 

 burniug is slow combustion, and this you are sure to ef- 

 fect if you can check it by addition to the heap. "When 

 the heap is fairly alight, put on more clay wherever the 

 smoke appears, but not too much at a time. This is con- 

 tinued until the heap is large enough, when the fire is 

 allowed to extinguish itself. 



CHAPTER VI. 



SUB-SOILING, TRENCH PLOWING, TILLAGE OPER- 

 ATIONS. 



SuBSOiT. Plowing : Deepenins: and Stirring;.— Trench Plowing. — Til- 

 lage OrEUATiuNs: Plowiuj^, Cultivating, Rolling, Steam-plowing. 

 —Depth of Tillage.— Stubble Cleaning. 



These operations tend to loosen the hard earth below 

 the reach of the ordinary plow, and to facilitate the 

 escape of water from the surface ; they promote the cir- 

 culation of air, and afford a more extended range for the 

 roots of tlie plants, by wliich they obtain additional 

 nourishmenc ; and tliey secure the crops against droutli, 

 by ciial)ling them to penetrate into the region of perpetual 

 moisture. 



