FORACxE CEOPS. 373 



and of ash-constituents of plants in the product of an acre, clover 

 is an excellent preparatory crop for wheat. 



" 4. During the growth of clover a large amount of nitrogenous 

 matter accumulates in the soil. 



" 5. This accumulation, which is greatest in the surface-soil, is 

 due to decaying leaves dropped during the growth of clover, and 

 to an abundance of roots, containing, when dry, from ij to 2 per 

 cent, of nitrogen. * 



" 6. The clover-roots are stronger and more numerous, and 

 more leaves fall on the ground when clover is grown for seed, than 

 when it is mown for hay ; in consequence, more nitrogen is left 

 after clover-seed than after hay, which accounts for wheat yield- 

 ing a better crop after clover-seed than after hay. 



" 7. The development of roots being checked when the produce, 

 in a green condition, is fed ofF by sheep, in all probability leaves 

 still less nitrogenous matter in the soil than when clover is allowed 

 to get riper and is mown for hay ; thus, no doubt, accounting for 

 the observation made by practical men that, notwithstanding the 

 return of the produce in the sheep-excrements, wheat is generally 

 stronger and yields better, after clover mown for hay, than when 

 the clover is fed off green by sheep. 



" 8. The nitrogenous matters in the clover-remains on their 

 gradual decay are finally transformed into nitrates, thus affording a 

 continuous source of food on which cereal crops specially delight 

 to grow. 



" 9. There is strong presumptive evidence that the nitrogen 

 which exists in the air in the shape of ammonia and nitric acid, 

 and descends in these combinations with the rain which falls on 

 the ground, satisfies, under ordinary circumstances, the require- 

 ments of the clover crop. This crop causes a large accumulation 

 of nitrogenous matters, which are gradually changed in the soil 

 into nitrates. The atmosphere thus furnishes nitrogenous food to 

 the succeeding wheat indirectly, and, so to say, gratis. 



" 10. Clover not only provides abundance of nitrogenous food, 

 but delivers this food in a readily available form (as nitrates) more 

 gradually and continuously, and consequently with more certainty 

 of a good result, than sucli food can be applied to the land in the 

 shape of nitrogenous spring top-dressing. 



" Laboratory, 1 1 SALisBuiiy Square, 



Fleet Strcet, E. C, July, 1868." 

 In addition to the foregoing, I extract the following from a 

 paper written by the Hon. Geo. Geddes for the New York Tri- 



