100 CARBONATE OF LIME. 



portion of all, varying however according to 

 the quantity existing in the soil in w^hich the 

 plants are cultivated. 



One of the most obvious purposes it serves, 

 is to give stability and substance, from its 

 earthy nature, to those parts of the plant, 

 which otherwise would not perhaps have 

 sufficient strength to perform the functions 

 allotted to them ; but that it possesses other 

 properties, there is little doubt, as it is found 

 not only in the stalk, but in the leaves, fruit, 

 and indeed in almost all parts of the plant. 



Carbonate of Lime, that is, lime combined 

 with carbonate acid gas, is the state in which 

 the substance most commonly exists ; in this 

 combination it is known to us under the names 

 of marble, chalk, marl, limestone &c., all being 

 lime combined to a greater or less extent with 

 carbonic acid gas. Chalk, we believe, is the 

 substance of this class which is most commonly 

 used as a manure, or in promoting vegetation. 

 We therefore shall confine ourselves to de- 

 scribing its use, and its mode of action, but, 

 with a fev/ slight modifications, the same re- 

 marks will apply to any of these substances. 

 In its ultimate analysis chalk yields, 

 55 parts of lime, and > .^ ^ ^^^ 



45 parts of carbonic acid gas, 5 j f ' 



and some extraneous matter, such as silex, and 

 oxide of iron. 



In this state it is very sparingly soluble in 

 cold water, but if water charged with carbonic 

 acid gas is present (and all water, as we have 

 before seen, (page 69) does contain this gas,) 



