ON MANURES. 77 



not, indeed, be doubted that, in whatever state it may be found 

 the most effectual, it is at least well worthy of attention, and 

 we recommend it strongly to the consideration of all experi- 

 mental farmers. 



CHAPTER IV. 



MINERAL MANURES. CHALK — LIME. 



The manures which we term alkaline and calcareous, con- 

 sist chiefly of those substances which combine with acids, 

 though generally with the loss of their distinctive characters, 

 and out of which lime may be extracted by the process of 

 burning. The extent of their utility is only ascertained by 

 practice, which does not speak a uniform language in every 

 place, for scarcely a farmer is to be found who is acquainted 

 with the exact effect of their properties upon soils ; from which 

 it may be readily imagined that many will form erroneous 

 opinions, arising out of the local circumstances of their own 

 farms. Their chief advantage, in a natural state, seems, how- 

 ever, to be rather mechanical and alterative, than nutritive. 

 They form a useful component part of the earth; and, in cer- 

 tain proportions, they are found to be essential to the fertility 

 of most soils, or 'perhaps necessary even to their proper tex- 

 ture, as an ingredient in the organs of plants.' The primitive 

 constituents of which they are formed are composed of chalk, 

 of limestone, or of the shells of fish — and on being submitted 

 to the action of fire, lime is produced. 



[Chalk — Is a pure calcareous earth, having the same pro- 

 perties as limestone ; but as it occurs in deposite to no extent 

 in this country, we have omitted any beyond this casual men- 

 tion of it.] 



Limestone. — If employed without being burned, its effects 

 upon the land are very slow : it acts upon the soil during many 

 years as a mild calcareous earth, but its duration and effects 

 are proportioned to its purity, as the less alloy which it con- 

 tains, the stronger will it be, and the operation of changing it 

 into lime is of no further use than as a mode of rendering it 

 more promptly effective. As a gradual improver of the soil, 

 it may even be rendered more useful than quicklime. 

 7* 



