\ BY MINERAL MANURES. 89 



narrow-leaved crops, as wheat, rye, timothy, &c., which 

 do not yield it on analysis ; and that it produces no bene- 

 ficial effect upon wet or heavy clay grounds. 



Judge Peters, of Pennsylvania, and John Taylor, of 

 Virginia, who multiplied experiments with gypsum, thought 

 that a bushel an acre, sown broadcast upon grass lands, 

 was a sufficient dressing. We have found two busiiels 

 an acre to be beneficial upon meadows. In arable hus- 

 bandry, gypsum is either sown broadcast, before the last 

 ploughing or harrowing, or put upon the plants in hilled 

 or drilled crops. 



Jllarl is another mineral substance which often induces 

 fertility. It is composed of carbonate of lime, com- 

 bined with sand or clay, and is deemed valuable in pro- 

 portion to the quantity of lime which it contains. 



Clay-marl occurs in beds, more or less indurated ; 

 and is sometimes so hard as to acquire the name of rock- 

 marl. These marls should be laid upon the surface, not 

 in heaps, but spread, that they may be well exposed to 

 the ripening influence of the atmosphere, and if to the 

 frosts of winter, the better. They have been found 

 sometimes to be injurious without this exposure. Their 

 operation is similar to that of mild lime, though slower. 

 This kind of marl is most beneficially applied to sandy, 

 gravelly, and peaty soils. It gives to such soils, what 

 they want, both lime and clay. To improve a soil, 20 

 or 30 loads of this marl are given to the acre ; but when 

 the object is to change the constitution of a defective 

 soil, doses of 300 to 400 cart-loads are given to the 

 acre. The best way is to spread it upon the sward, 

 where it remains until the land is brought under tillage. 

 We have used the blue clay, containing 25 to 30 per 

 cent, of the carbonate of lime, upon blowing sands, at 

 the rate of 20 loads the acre, to very great advantage ; 

 and consider its ultimate benefit greater than that of an 

 equal quantity of stable-dung. When taken to the field 

 it should be immediately scattered upon the surface ; the 

 frost and weather so divide and break it down, that, when 

 dry, it may be broken into powder, with but little labor. 



Shell-marl is a deposit of marine, and sometimes of 

 8* 



