404 ACTION OF CAUSTIC LIME UPON ORGANIC MATTER 



Hence one of the benefits which result from the use of wood-ashes 

 containing carbonate of potash, when employed in small quantities, 

 and along with vegetable and animal manures, as they are in this coun- 

 try ; but hence also the evil effects which are found to follow from the 

 application of them in too large doses. Thus in countries wher& wood 

 abounds, and where it is usual, as in Sweden and Northern Russia, 

 to burn the forests and to lay on their ashes as manure, the tillage 

 can be continued for a few years only. After one or two crops the 

 lairtl is exhausted, and must ag 'm be left to its natural produce. 



§ 26. Special efects of cavstu lime upon the several varieties of 

 organic matter in the soil. 



The eftects of lime upon organic matter are precisely the same 

 in kind as those of the alkaUes in general. They are only less in de- 

 gree, or take place more slowly, than when soda or potash is em- 

 ployed. Hence, the greater adaptation of lime to the purposes of 

 practical agriculture. 



1°. Action of caustic lime alone upon vegetable matter. — If the fresh 

 leaves and twigs of plants, or blades and roots of grass, be introduced 

 into a bottle, surrounded with slaked lime, and corked, they will slowly 

 undergo a certain change of color, but they may be preserved, it is 

 said, for years, without exhibiting any striking change of texture (Mr. 

 Garden.) If dry straw be so mixed with slaked lime, . - will exhibit 

 still less alteration. In either case also the changes will be even less 

 perceptible, if instead of hydrate of lime, the carbonate (or 7nild lime.) 

 in any of its forms, be mixed with these varieties of vegetable matter. 

 On some other varieties of vegetable matter, — such, for example, as are 

 undergoing rapid decay, or have ai ready reached an advanced stage of 

 decomposition, — an admixture of slaked hme produces certain percepti- 

 ble changes immediately, and mild lime more slowly, but these changes 

 being completed, the tendency of lime alone is to arrest rather than to 

 promote further rapid alterations. Hence, the following opinions of 

 experienced practical observers must be admitted to be theoretically 

 correct — in so far as they TeSt$ to the action of lime alone. 



" If straw of long dung be mixed with slaked lime, it will be pre- 

 served." (Morton, On Soils, 3d edition, p. 181.) 



" Lime mixed in a mass of earth containing the live roots and seeds 

 of plants, will 7iot destroy them." (Morton.) 



" Sir H. Davy's theory, that lime dissolves vegetable matter, is 

 given up ; in fict, it hardens vegetable matter. (Mr. Pusey, Royal 

 Agricultural Journal, iii., p. 212. 



These opinions, I have said, are probab.y correct in so far as re- 

 gards the unaided action of lime. They even express, with an ap- 

 proach to accuracy, what will take place in the interior of compost 

 neaps of a certain kind, or in some dry soils ; but that they cannot 

 apply to the ordinary action of lime upon the soil is proved by the 

 other result of universal observation, that lime, so far from preserv- 

 ing the organic matter of the land to which it is applied, in reality 

 wastes it — causes, that is, or disposes it to disappear. 



2=*. Action ofca.ustic lime on organic matter in the presence of air 

 and. 'Water. — In the presence of air and water, when assisted by a 



