ON MANURES. 89 



surface of the soil which cannot be easily broken. Thus, when 

 such land has been frequently limed, nothing can restore it 

 but the abundant and reiterated application of putrescent 

 manure; the demonstration of which is perceptible throughout 

 many parts of England, where, from possessing a chalky soil 

 without strength to maintain a sufficiency of live stock to 

 furnish dung, the land has in many places been worn out 

 through the inconsiderate use of lime. 



On the exhaustion of land by the application of lime there 

 is, however, much difference of opinion. It is indeed evident 

 that the continuation of cropping, without an addition of nutri- 

 tive manure, will ultimately exhaust the best soils; but though 

 their natural fertility be thus aided, it yet cannot depend en- 

 tirely on that support. This must be apparent if we reflect 

 that land, v/ithout any addition of animal or vegetable sub- 

 stance, will still produce crops: for pure sand, clay, and chalk, 

 tliough each in themselves separately barren, yet, when mixed 

 together, exert chemical influences upon each other, which, 

 by the attraction of the air, the dews, and the rain, the force 

 of the sun, and the generative powers of growing vegetables, 

 effect the production of corn and fruit. It is therefore clear 

 that the land alone is capable of vegetation; but every day's 

 experience proves, that the amount of its products, its fertility, 

 in short, depends in a great degree upon the decomposition of 

 the substances which have been previously converted into 

 vegetable mould, or which are added to it by manure. Any 

 thing whatever may be called manure which, when applied 

 to the soil, either rectifies its mechanical effects, corrects any 

 bad quality, and either stimulates it to yield, or stores it with 

 nutriment. Thus, if lime be laid upon pure sand, although 

 the latter would be rendered more tenacious, and would there- 

 by become, more favourable to the germination of vegetables, 

 yet seeds could find no nourishment from either the lime or 

 the sand, and putrescent manure would still be necessary to 

 produce a crop. But if the soil consist of. clay and sand, con- 

 tainino- animal or veg€||able matter in a torpid state of decay, 

 then lime would be preferable to dung. The state of the soil 

 should therefore be minutely inquired into before lime is em- 

 ployed, and it should be only used to give effect to the inert 

 substances with which it may be combined. 



By the analysis of soils, we find that all productive earth 

 contains a certain portion of lime; and although we learn 

 from experience that its stimulative powers upon the roots of 



