152 Review of Essays on Calcareous Manures. 



H The formation of nitric acid in calcareous soils, by the absorption 

 of its two elements from the atmosphere, is not only rendered proba- 

 ble by the presence of nitre and nitrate of lime in the soils of many 

 warm countries, but made certain by the construction of artificial 

 nitre beds in France, when the foreign supply was cut off by the 

 preponderance of the British navy. When this acid is formed in a 

 soil abounding with vegetable matter, not yet decomposed, as is the 

 case with many of our newly opened regions, oxalic acid must be 



formed. 



Such then are the properties of lime, considered as a constituent 

 of the soil : to bring its texture to that best suited for tillage, and 

 for conveying the moisture, which is the vehicle of the food of 

 plants, neither in excess or in defect ; to condense and store up that 

 gaseous food until needed ; to promote the decomposition of inert 

 organic matter ; to neutralize acidity, and counteract its antiseptic 

 action, thus removing a noxious principle, and opening a new supply 

 of vegetable food. 



One other use of lime in soils remains to be mentioned, and this 

 does not seem to have occurred to Mr. Ruffin, but is strongly urged 

 by M. Puvis, in a passage we have quoted. The ashes of all plants, 

 when lixiviated, are composed either of the pure earths or earthy 

 salts ; of the latter, those of lime are by far the greatest in quantity, 

 although probably altered by the fire from their original state. Thus, 

 wood ashes contain the carbonate, sulphate, and phosphate of lime. 

 In addition, the liquor by which the alkaline matter is separated by 

 lixiviation carries with it earthy matter, which is rendered soluble by 

 the alkali. Now it cannot be doubted, that if this alkaline, earthy 

 and saline matter is not contained in the soil, the plant must be stint- 

 ed in its growth or actually die. Thus, to many plants, lime or some 

 of its compounds forms an essential article of food ; it may be re- 

 quired in less quantity than carbon, hydrogen, oxygen, and water, 

 but is not the less necessary to their growth. Now, former analyses 

 did not shew, that lime and its compounds are contained in the stalks 



srramma 



> 



undissolved by water or alcohol, or left as a residuum of combustion, 

 was well known. More recent investigations have shewn, that lime 

 is one of the constituents of this residuum. Silex certainly exists 

 in the stalks, and particularly at the joints of the graraina, being in 

 some actually visible to the naked eye. 



