1838] 



FARMERS' R K G I S T 10 R 



651 



emits a fetid smell if rubbed, it contains coally or 

 bituminous matter. 



The analysis of limestones is not a difficult mat- 

 ter ; and the proportions of their constituent pans 

 may be easily ascertained by the process described 

 in the lecture on tlic analysis oC soils; and usually 

 with sullicient accuracy lor all the purposes ol" the 

 larmer, by the filth process. 



Before any opinion can be formed of the manner 

 in which the ditii!rent ingredients in limestones 

 modify their properties, it will be necessary to 

 consider the operation of" the pure calcareous ele- 

 ment as a manure, and as a cement. 



Quicklime in its pure stale, whetlier in powder 

 or dissolved in water, is injurious to plants. I 

 have in several instances Killed grass by water- 

 ing it with lime-water. But lime, in its state of 

 combination with carbonic acid, as is evident from 

 the analysis given in the fourth lectiire, is a useflil 

 ingredient in soils. Calcareous earth is found in 

 the ashes of the greater number of plants ; anil 

 exposed to the air lime cannot long continue caus- 

 tic, for the reasons that were just now assigned, 

 but soon becomes united to carbonic acid. 



When newly burnt lime is exposed to air, it 

 soon liills into powder ; in this case it is called 

 slacked-lime ; and the same effect is immediately 

 produced by I browing water upon it, when it heats 

 violently, and the water dissappears. 



Slacked-lime is merely a combination of lime 

 with about one-third of its weight of water; i. c. 

 55 parts of lime absorb 17 parts of water; and in 

 this case it is composed of a definite proportion of 

 lime to a definite proportion of water, and is called 

 by chemists hydrate nf lime; and when hydrate of 

 !ime becomes carbonate of lime by long exposure 

 to air, the water is expelled, and the carbonic acid 

 gas takes its place. 



When lime, whether freshly burnt or slacked, is 

 mixed with any moist fibrous vegetable matter, 

 there is a strong action between the lime and the 

 vegetable matter, and they form a kind of com- 

 post together, of which a part is usually soluble in 

 wafer. 



By this kind of operation, lime renders matter 

 which was before comparatively mert nutritive; 

 and as charcoal and oxygen abound in all vegeta- 

 ble matters, it becomes at the same time converted 

 into carbonate of lime. 



Mild lime, powdered limestone, marls or chalks, 

 have no action of this kind upon vegetable matter ; 

 by their action they prevent the too rapid decom- 

 position of substances already dissolved ; but they 

 have no tendency to form soluble matters 



It is obvious from these circumstances, that the 

 operation of quicklime, and marl or chalk, de- 

 pends upon principles altogether different. Quick- 

 lime, in being applied to land, tends to bring any 

 hard vegetable matter that it contains into a state 

 of more rapid decomposition and solution, so as 

 to render it a proper food for plants. Chalk, and 

 marl, or carbonate of lime, will only improve the 

 texture of the soil, or its relation to absorption : 

 it acts merely as one of its earthy ingredients. 

 Quicklime, when it becomes mild, operates in the 

 same manner as chalk ; but in the act of becom- 

 ing mild, it prepares soluble out of insoluble 

 matter. 



It is upon this circumstance that the operation 

 of lime in the preparation for wheat crops de- 

 pends ; and its efficacy in fertilizing peats, and in 



bringing into a state of cultivation all soils abound- 

 ing in hard roots, or dry fibres, or inert vegetable 

 matter. 



The solution of the question, whether quicklime 

 ouiiht to be applied to a soil, depends upon the 

 quantity of inert vegetable matter thnt it contains. 

 The solution of the question, whether marl, mild 

 lime, or powdered limestone, ought to be applied, 

 depends upon the quantity of calcareous matter 

 already in the soil. All soils are improved by 

 mild lime, and ultimately by quicklime, which do 

 not effervesce with acids ; and sands more tfian 

 clays. 



VVhen a soil, deficient in calcareous matter, 

 contains much soluble vegetable manure, the ap- 

 plication of quicklime should always be avoided, 

 as it either tends to decompose the soluble matters 

 by uniting to their carbon and oxygen so as to be- 

 come mild lime, or it combines with the soluble 

 matters, and forms compounds, having less attrac- 

 tion for water than the pure vegetable substance. 



The case is the same with respect to most ani- 

 mal manures ; but the operation of the lime is dif- 

 ferent in different cases, and depends upon the na- 

 ture of the animal matter. Lime forms a kind of 

 insoluble soap with oily matters, and then gradu- 

 ally decomposes them by separating from them 

 oxygen and carbon. It combines likewise with 

 the animal acids ; and probably assists their de- 

 composition by abstracting carbonaceous matter 

 from them combined with oxygen : and conse- 

 quently it must render them less nutritive. It 

 tends to diminish likewise the nutritive powers of 

 albumen from the same causes ; and always de- 

 stroys to a certain extent the efficacy of animal ma- 

 nures, either by combining with certain of their 

 elements, or by giving to them new arrangements. 

 Lime should never be applied with animal ma- 

 nures, unless they are too rich, or for the purpose 

 of preventing noxious effluvia, as in certain cases 

 mentioned in the last lecture. It is injurious when 

 mixed with any common dung, and tends to ren- 

 der the extractive matter insoluble. 



I made an experiment on this subject : I mixed 

 a quantity of the brown soluble extract, which 

 was procured from sheep's dung, with five times 

 its weight of quicklime. I then moistened them 

 with water ; the mixture heated very much ; it 

 was sufTered to remain lor 14 hours, and was then 

 acted on by six or seven times its bulk of pure 

 water : the water, after being passed through a 

 filter, was evaporated to dryness ; the solid mat- 

 ter obtained was scarcely colored, and was lime 

 mixed wuh a little saline matter. 



In those cases in which fermentation is useful 

 to produce nutriment from vegetable substances, 

 lime is always efficacious. I mixed some moist 

 tanners' spent bark with one-fifih of its weight ol 

 quicklime, and suffered them to remain together 

 in a close vessel for three months ; the lime had 

 become colored, and was efl^ervescent : when wa- 

 ter was boiled upon the mixture, it gained a tint 

 of fawn-color, and by evaporation fiirnished a 

 fawn-colored powder, which must have consisted 

 of lime united to vegetable matter, for it burnt 

 when strongly heated, and left a residuum of 

 mild lime.* 



* The manner in which lime acts in agriculture re- 

 quires further and minute investigation, and is a most 

 important subject for inquiry. From the experimonts 



