9G PRESERVING AND FIXING MANURES. 



or decomposing the animal substance (and nearly destroying it as 

 manure), before putrefaction begins. The operation of calcareous 

 earth is to moderate and retard, but not to prevent putrefaction ; 

 not to destroy the animal matter, but to preserve it effectually, by 

 forming new combinations with the products of putrefaction. This 

 important operation will be treated of more fully in a subsequent 

 chapter. 



The power of calcareous earth to combine with and retain putres- 

 cent manure, implies the power of fixing them in any soil to 

 which both are applied. The same power will be equally exerted 

 if the putrescent manure is applied to a soil which had previously 

 been made calcareous, whether by nature, or by art. When a 

 chemical combination is formed between the two kinds of manure, 

 the one is necessarily as much fixed in the soil as the other. 

 Neither air, sun or rain, can then waste the putrescent manure, be- 

 cause neither can take it from the calcareous earth, with which it 

 is chemically combined. Nothing can effect the separation of the 

 parts of this compound manure, except the attractive power of 

 growing plants which, as all experience shows, will draw their 

 food from this combination as fast as they require it, and as easily 

 as from sand. The means then by which calcareous earth acts as 

 an improving manure are, completely preserving putrescent manures 

 from waste, and yielding them freely for use. These particular ' 

 benefits, however great they may be, cannot be seen very quickly 

 after a soil is made calcareous, but will increase with time, and, 

 with the means for obtaining vegetable matters, until their accu- 

 mulation is equal to the soil's power of retention. The kind, or 

 the source, of enriching manure, does not alter the process de- 

 scribed. The natural growth of the soil, left to die and rot, or 

 other putrescent manures collected and applied, would alike be 

 seized by the calcareous earth, and fixed in the soil. 



This, the most important and valuable operation of calcareous 

 earth, then gives nothing to the soil ; but only secures other ma- 

 nures, and gives them wholly to the soil. In this respect, the 

 action of calcareous earth in fixing manures in soils, is precisely 

 like that of mordants in "setting" or fixing colours on cloth. 

 When alum, for -example, is used by the dyer for this purpose, it 

 adds not the slightest tint of itself but it holds to the cloth, and 

 also to the otherwise fleeting dye, and thus fixes them permanently 

 together. Without the mordant, the colour might have been 

 equally vivid, but would be" lost by the first wetting of the cloth. 



[Thus, reasoning a priori from that chemical power possessed 

 by calcareous earth, which is wanting to both sandy and clayey 

 earths, would lead to the conclusion that calcareous earth serves to 

 combine putrescent matters with the soil in general; and the 

 known results of fertility being therein so fixed, might serve for 



