ACTION OF SALTS. Il5 



silicates ; and the alkalies of the silicates are eliminated. 

 These solve or decompose the geine and geates, which the 

 lime had locked up; at the same time the silicic acid acts on 

 the carbonate of lime, volumes of carbonic acid are let loose. 

 The carbonic acid itself reacts on silicates, eliminating afresh 

 portion of alkali, and upon the geates, converting these into 

 super-geates. A round of change goes on, till perhaps every 

 particle of vegetable food is withdrawn ; crops are no longer 

 raised. Having witnessed, though slow to believe it, good 

 effects from liming, the farmer again applies it to the ex- 

 hausted field ; but no good effects can now follow, unless 

 manure or decayed vegetable matter is also applied. This 

 may be furnished in two ways, either artificially or naturally, 

 that is, by allowing the scanty crop of all sorts of weeds, 

 grass, mullein, &c., to decay on the soil where it grew. But 

 this subject will be considered in another place. 



162. It has been attempted to show how the contradictory 

 and anomalous effects of lime are explicable, on the princi- 

 ple (145) ; and here the general theory of the action of lime 

 may be adverted to, much of which has been anticipated. 

 Lime is a general term, it includes all forms of calcareous 

 matter. It is the lime, the base of the salts which acts, and 

 that always, as lime, no matter how it is applied ; whether 

 as marble, as marl, shells, air-slacked lime, bones or plaster. 

 In a restricted and usual acceptation of the term, lime refers 

 only to that which has been burned, or stone lime. Its 

 action is threefold, each distinct, first, as a neutralizer — 

 secondly, a decomposer — thirdly, a converter. 



1st. Wherever free acids exist in soil, lime acts as a neu- 

 tralizer. It has been asserted, on undoubted authority, that 

 occasionally free phosphoric, muriatic, geic, acetic, and malic 

 acids exist in soil. 



2d. Soil may contain abundant geates, particularly geate 



