No. 9. 



Lime and Magnesia. 



267 



In regard to the first, the following ex- 

 tracts from the work just named, may be 

 placed before those who say magnesia acts 

 as a poison to vegetation. 



1st. "Phosphate of magnesia, in combi- 

 nation with ammonia, is an invariable con- 

 stituent of the seeds of all kinds of grasses. 

 It is contained in the outer horny husk, and 

 is introduced into bread along with the flour, 

 and also into beer. The bran of flour con- 

 tains the greatest quantity of it. It is this 

 salt which forms large crystalline concre- 

 tions, often amounting to several pounds in 

 weight, in the ccecum of horses belonging 



to millers.' 1 "Most plants, perhaps all 



of them, contain organic acids of very dif- 

 ferent composition and properties, all of 

 which are in combination with bases, such 

 as potash, soda, lime, or magnesia." 



2nd. In explanation of the reason why 

 wheat will not grow in a soil of humus 

 alone, Liebig says, "The cause is this, — the 

 strength of the stalk is due to the silicate of 

 potash, and the corn requires phosphate of 

 magnesia, neither of which substances a soil 

 of humus can afford, since it does not con- 

 tain them ; the plant may, indeed, under 

 such circumstances become an herb, but 

 will not bear fruit." 



3d. "Most seeds contain certain quantitie 

 of phosphates. In the seeds of different 

 kinds of corn, particularly, there is abun- 

 dance of the phosphate of magnesia." 

 Again, "It is evident the seeds of corn 

 could not be formed without phosphate of 

 magnesia, which is one of their invariable 

 constituents." 



" The ashes both of peat and coal, contain 

 in general magnesia; hence their value as 

 an ingredient of prepared night soil. When 

 magnesia is not present it. will be necessary 

 to add some magnesian limestone or epsom 

 salts." "Phosphates of magnesia and am- 

 monia, form the principal inorganic constitu- 

 ents of the potatoe." 



' I might continue the extracts ; but these 

 are sufficient to show, how very "hurtful" 

 lime and magnesia must be to plants when 

 taken up as food ; the following will show 

 our writer's opinion of its usefulness in the 

 ■soil. 



" In a soil to which air has no access, or 

 at most, but very little, the remains of ani- 

 mals and vegetables do not decay, for they 

 can only do so, when freely supplied with 

 oxygen ; but they undergo putrefaction, for 

 which air is present in sufficient quantity. 

 Putrefaction is known to be a most powerful 

 leoxidizing process, the influence of which, 

 sxtends to all surrounding bodies, even to 



ihe roots and the plants themselves." 



The frequent renewal of air by plough- 





ing and the preparation of the soil, especially 

 its contact with alkaline metalic oxids," — 

 of which magnesia is one, — "the ashes of 

 brown coal, burnt lime, or limestone, change 

 the putrefaction of its organic constituents, 

 into a pure process of oxidation ; and from 

 the moment at which all the organic matter 

 existing in a soil, enters into a state of oxi- 

 dation or decay, its fertility is increased." 



In speaking of the decay of the excre- 

 ments of vegetables, which when they ac- 

 cumulate in a soil act injuriously, and fre- 

 quently to the exclusion, or " running out," 

 of the plant which exudes them, he says: 

 "The quickness with which this decay of 

 the excrements of plants proceeds, depends 

 upon the composition of the soil, and on its 

 greater or less porosity. It will take place 

 very quickly in a calcareous soil," (or I will 

 add, a soil impregnated with magnesia:) 

 "for the power of organic excrements to 

 attract oxygen and to putrify," (decay*) " is 

 increased by contact with the alkaline con- 

 stituents." 



The gentleman of the " golden plough," 

 seems to view lime and magnesia, only in 

 the light first above considered, when he 

 asks, would it be advised "to apply 100 

 bushels of plaster to the acre?" And, by 

 the way, if he accounts for the action of 

 plaster upon clover, as his arguing would 

 seem to indicate, solely by its affording, in 

 itself, a food for that plant, he is there, at 

 least, far behind the times. Tell him that 

 its use is to combine with, and fix the am- 

 monia of the rain water, &c, and that a 

 small quantity upon the surface is sufficient 

 for the time being, to answer that end ; and 

 let him learn above, that "alkaline constitu- 

 ents" should pervade all parts of a soil, and 

 he will himself perceive why more lime is 

 required than gypsum. 



As ingredients for the improvement of the 

 soil itself, much larger quantities of these 

 alkaline earths may be necessary, than the 

 plants require for food. But what is a large 

 quantity? Our friend speaks of the best 

 English soils containing but one or two per 

 cent, of lime, and calls that a small quan- 

 tity. Now upon calculation, it will be found 

 that in a soil six inches deep, one per cent., 

 considering the lime as heavy as the other 

 earthy ingredients of the soil, is equivalent 

 to about 175 bushels to the acre, and of 

 course, two per cent, is 350 bushels to the 

 acre; which is at least not so small as "50 

 bushels." 



* It is plain that the proper distinction explained in 

 the work, between "putrefaction" and "decay," was 

 here overlooked; "decay" being evidently in this case 

 alluded to. 



