242 



NEW ENGLAND FARMER, 



FEBRDART 6, 18.9. 



(loos exist which tgnds combine them. The silica tion called marling. Jlarl is not a simple mixture and in superficial portions of the earth, penetrated 

 and alumnia are, in relation to the lime, electro- of silica and alumina with more or less of carbo- by the air, we may conceive it to be formed by the 

 negative bodies, and in their presence the lime nate of lime. Its ba?e is argillaceous and caica- re-action of oxygen upon the carbon of organic 

 must acquire a contrary electricity. According as : reous silicates; some mineralogists consider it detritus ; but at those great depths which are at- 

 e.xternal or mechanical movements of the soil, or | even as an oryclognosaical species.* It is on this tained by the roots of oaks and cedars of a hun 

 other foreign causes, shall bring these molecules account that plants cannot vegetate in marl which 

 within greater or less distances from each other, has been long exposed to the air, even when the 

 and group them in various ways, electrical piles silica, alumina and lime are in tlie proportions 



which form good ara,ble land. By exposure to the 



The radical I reous soils 



will be established, discharges will take place, pro 

 ducing various tensions, and the earth will thus, if 

 we may use the ter:M, become animated. The 

 electric fluid which pervades it will excite the sto- 

 mata of the radical fibrils, determine the play of 

 the organs, and the absorption of the fluids requi 

 site to the nourisliinent of the plant. 

 fibrils, at.d the capillary roots impregnated with 

 moistui-e, will become so many. electrical conduc- 

 tors, engaged in transmitting electricity, tertamly 

 as necessary to life as light and caloric. 



The merit of a theory is, that it accounts for 

 observed facts, enables us to forsee what will take 

 place under particular circumstances likely t« bap- 

 pen, and indicates tiie considerations which it may 

 bo desirable to bring about with a view to useful 

 results. 



Let us inquire whelbcr the theory now presented, 

 ■fulfils these conditions : 



Suppose a chalky soil. To improve it, we add 

 ■ argillaceous marl ; i. e. to the lime which predom- 

 ■JBates we add silica and alumina. To the pontht 

 eUmcni which we found atone, tix add the negative 

 elements ivkich we found deficient. 



Will it here be said, that "chalk is so compact 

 that the roots cannot i>enetrate it, or so split up 

 that water passes tlirough it like a riddle, and that 

 the marling is simply designed to change this phy- 

 sical condition ?* 



But, if the object was merely to divide-the chalk, 

 in order to change its physical condition, a calca- 

 reous sand would accomplish this object, and yet 

 it uever came into the head of an agriculttirist to 

 improve his chalk by limestone, while Gordan de 

 Saint-Memin produced a magnificent vegetation by 

 a mixture of chalk with heath sand. 



In a piece of ground belonging to Chaptal, the 

 soil was clayey and rather barren ; below was a 

 layer of black earth. Chaptal went to work em- 

 pirically, dug up the ground and mixed the two 

 beds togLlhci. Coatray to his expectations, the 

 sterility was increased. It was not till the fiftli 

 year that the ground acquired a common degree 

 of fertility, that is, when all the iron had passed to 

 tlio state of peroxide, and the land, black as it 

 was, had become of a deep, bright yellow, Chap- 

 tal asks, if, in this case, the black oxide is injurious 

 to vegetation, eitlier by itself, or in reference to 

 the oxygen. 



In our theory, the fact explains itself, and might 

 have been foreseen ; the black oxides of iron (fer 

 oxidule d' Hauy) is a combination of protoxide and 

 sesquioxide of iron, a substance indifferent in rela- 

 tion to silica and alumina. Exposed to the air, the 

 combination is destroyed, the iron passes to the 

 state of peroxide, susceptible of union with silica 

 and alumina. Yet, under such circumstances, it 

 was not worth while to mingle the two beds, since 

 five years were lost in attaining a common degree 

 of fertility. 



The theory which we have adopted, is applica- 

 ble, likewise, in the happiest manner, to the opera- 



• G. Diet, d' Agriculture, article Craie. 



dred years old, how can the carbonic acid be devel- 

 oped ? How can the oxygen and organic matter 

 penetrate to such depths ? In our i heory there is 

 no difficulty. Carbonic acid comes from the lime, 



air, carbonic acid distroys the comhinnfion which on wliich the silica and alumina act slowly but 



existed between the earths, and it is then, and then 

 only, that marl will enrich the soil. In this case, 

 if the negative element pruvails, as in the case of 

 argilliceous marks, it becomes excellent for calca- 

 and marls called calcareous are in 

 their turn advantageous for argillo-sandy land. 



It has been remarked, that the alkaline and 

 earthy salts, which, in a certain quantity, injure 

 vegetation, produce a good effect -when employed 

 in small doses. Chemists and farmers have sought 

 to explain this action of saline compounds. Some 

 have thought that certain salts were good for plants, 

 as some are for animals — that salts, and even 

 earths, formed part of the food of vegetables ; 

 others, on the contrary, that they act principally as 

 stimulants to vegetation. Without denying that 

 earthy substances may enter into the constitution 

 of a vegetable, to unite and give strength to tlie 

 parts tliat are to support the organs, like phosphate 

 of lime in the bones of quadrupeds, I may remark, 

 that with a few exceptions, the presence of any 

 salt is not absolutely necessary to vegetation. Thus, 

 for example, borage and lettuce, ^i||iose extracts 

 contain much nitre when they grow in highly ma- 

 nured soils, do not contain any sepsible portion of 

 it when cultivated without dung. I therefore rath- 

 er incline to the opinion of physiologists, who 

 think with M. DecandoUe, that salts act as exci- 

 tants or stimulants. But, what is the meaning of 

 excitation ? At the present day, science no longer 

 admits of those vague explanations which consist 

 of nothing but words. I understand by excitation, 

 the eminent property of conducting electricity 

 which salts communicate to water. It is in this 

 manner, as it appears to me, that nitrate of potash 

 acts, in the prodigious energy which it gives to 

 vetretation. It is probable in this way that sulphate 

 of lime acts; that is to say, by rendering the water 

 a better conductor, though, in this case, the effects 

 ap]iear to me to be complicated, and to be worthy 

 of direct experiment 



Thus far, for greater simplicity, wc have consid- 

 ered lime as free, in speaking of the mixture of 

 silica, alumina, and lime, which constitute a soil ; 

 now the lime is in the state of carbonate, but it 

 does not, in that state cease to be an electro-posi- 

 tive element in relation to silica and alumina. 

 This circumstance allows us to explain an impor- 

 tant vcgeto-physiological fact The carbon in veg- 

 etables is produce!! mostly, if not entirely, by the 

 decomposition of the carbonic acid which they 

 ab.aorb not only from the air, but from the ground: 

 such is the opmion of the celebrated DecandoUe. 

 This carbonic acid, furnished by tlie ground, ap- 

 pears to enter into the vegetable at the moment of 

 its liberation, probably dissolved in the water which 

 the soil contains. It is absorbed by the spongioles 

 of the radicules ; it ascends with the sap, urged 

 forward as by a vis a tergo. But how is this car- 

 bonic acid produced ? In certain manured soils^ 



continuously to form silicates.* 



Thus, then, at certain depths, and under influences 

 but little understood, silica would decompose car- 

 bonate of lime, while at the surface of the earth, 

 and under the influence of exterior agents, the 

 silicates would be decomposed by carbonic acid 

 produced by the re-action of the oxygen of the air 

 on organic detritus — an admirable and pi eviden- 

 tial rotation, which re-establishes the equilibrium, 

 and incessantly tends to the rejuvenescence of 

 nature. 



The last corollary of my theory — the decompo- 

 sitioB of silicates by exterior agents, and particu- 

 larly by carbonic acid, cannot be called in question. 

 It lias been establislied by M. Becquerel, under 

 circumstances in which the force of cohesion might 

 seem to present a serious obstacle, I allude to the 

 decomposition of the feldspar of granite, and the 

 formation of kaolin. The asalogy is here so strong 

 that I must render the homage of my first concep- 

 tion to the distinguish academician I have just 

 cited. 



The fact of the decomposition of carbonate of 

 lime by silica in tlio interior of the earth is equally 

 supported by experiment and observation. And, 

 first, if, in proceeding to the analysis of a vegeta- 

 ble soil, when the coarser siliceous sand has been 

 separated by agitation and deposition, and the car- 

 bonate of lime has been removed by weak acids, 

 we examine the finer terrene substance which has 

 resisted the weak acids, we find that it is not alu- 

 mina, as Chaptal indicates, nor silica, as is stated 

 in various works, but tliat it consists principally of 

 veritable silicates of lime, of alumina, and of oxide 

 of iron. 



Still, it may be objected that these silicates are 

 anterior to all vegetation; that to piove tlieir re- 

 cent formation and daily production, requires di- 

 rect experiments. These direct experiments are 

 among the objects which I wish to undertake. 

 They require much time. But to prove truth, are 

 we to depend solely upon new experiuienis pecu- 

 liar to him who advocates it, and are we fobiddeni 

 to rely on the labors of our predecessors .' Cer- 

 tainly not. I may therefore again refer to the in- 

 teresting researches of M. Becqucret, and bringi 

 into view those mineral species which he has 

 formed in his laboratory, and which present all 

 the characters of their natural congeners. Nei- 

 ther can I omit to inention the important fact of' 

 the artificial formation of feldspar by Cagnard de^ 

 La tour. 



• Brochant's JUineralogy. 



* Animal manures may contribute lo the decompositioii 

 of silicates, not only by the carbonic acid which thej 

 form by absorbing oiygcB from the air, but in producing 

 sueli substances as the yAT acids, which liave a teudeiicy 

 lo unite with the lime and to eliminate the silica which 

 is combined with it. M. Rasiiail, whose talents we are 

 glad to acknowledge, without sharing in all his scientific 

 opinions, appears to us to have explained the sihceoui 

 petrefactions that are found in chalk, in a very liappj 

 manner by the action of animals entombed in siliceo. 

 calcareous beds. — Physiol. Vegetate, t 2. p 339. 



