1S38] 



FARMERS' REGISTER. 



727 



be enriched, ami are valuable only in moist climates. 

 Land origiiiatinii: in I lie decomposition of trap, ba- 

 salt and oilier rocks of complicated elements, pos- 

 sess, on the contrary, (jreat natural lerlilily. 



"Rivers," he Jijrtlier atlds, "receive in their 

 courses other streams whose mud is mintrled wiili 

 its own, and it often happens that the united sedi- 

 ment of two rivers possesses greater lertility than 

 that of either separately." 



This then appears to be an estabiiehed fact, that 

 a soil (independently of organic matter') is the 

 more fertile as its composition is more heterogene- 

 ous. 



If we seek (or an explanation of this fact, we 

 find in authors only vague opinions and doubts ; 

 the greater number merely stale the lijcts without 

 attempting an explanation. 



Agricultural chemists, who indulge more in 

 theory, appear to regard the cause of fertility as 

 dependent on the physical character of the soil 

 rather than on its chemical constitution. Thus 

 Davy having observed that different soils attract 

 moisture with different degrees of energy, and 

 having discovered, as he believed, that the most 

 hygrometric soils were the most fertile, he ascribes 

 their superior lertility chiefly to this property. But 

 Davy has not proved that the hygrometric force 

 of a soil bears any given relation to its composi- 

 tion. 



If this attraction of moisture were the princi- 

 pal cause of fertility (abating the influence of ma- 

 nures) we perceive no necessity for the combina- 

 tion of ihe three earths in the constitution of a soil 

 of the first quality. Indeed a certain quantity of 

 alumina in a soil otherwise entirely siliceous, or 

 entirely calcareous, a certain proportion between 

 the adhesive and the loose or sandy portions, 

 would be sufficient to confer this hygroscopic qua- 

 lity, and of course the fertility of the soil. Eut 

 we have nothing to confirm this supposition. 



The hygroscopic quality of a ternary soil may 

 then be considered as an element of fertility, but 

 only a secondary element, subordinate to its che- 

 mical composition. 



The property of becoming more or less heated 

 by the rays of the sun, which appeared (o Davy 

 to hold a relation to the fertility of different soils, 

 appears to me to be also a secondary cause. In 

 the cases referred to by him there was a mixture 

 of black mould, and he did not sufficiently consi- 

 der its fertilizing action as a manure upon the soil. 



To nfie, it appears evident, that the mixture ol 

 the various earths which compose a soil, acts upon 

 vegetation and determines its fertility bxj an elec- 

 tro-chemical force, whose action has' been clearly 

 recognized ni other circumstances, but not yet 

 brought into view in the case now under consi- 

 deration. In the first place, let us observe, that it 

 is a flict, though the truth may have escaped ob- 

 servers, or rather, it has not yet been broufjlit un- 

 der a formula, that the silica, alumina and lime 

 which enter into a good vegetable soil, must not 

 be combined with each other, but simply mixed, 

 the lime being in the state of a carbonate. A tri- 

 ple silicate of lime or alumina, in which the silex, 

 lime and alumina should be in the proportions 

 which constitute the best arable land, could not, 

 even if thoroughly divided, furnish a soil essenti- 

 ally adapted to vegetation. If, in a fertile soil, 

 composed of a mixture of lime, alumina and sili- 

 ca, a combination between these three oxides 



should begin to take place, the ground would be- 

 come cold and steril. Now, it is certain, that in 

 a mixture of these three ingredients, a liiice does 

 exist which tends to combine them. The silica 

 and alumina are, in relation to the lime, electro- 

 negative bodies, and in their presence the lime 

 must acquire a contrary eleclriciiy. According as 

 external or mechanical movements of the soil, or 

 other Ibreiijn causes, shall bring these molecules 

 within greater or less distances from each other, 

 and group them in various ways, electrical piles 

 will be established, discharges will take place, pro- 

 ducing various tensions, and the earth will thus, if 

 we may use the term, become animated. The 

 electric fluid vvhich pervades it will excite the gto- 

 mata of the radical fibrils, determine the play of 

 Ihe organs, and the absorption of the fluids requi- 

 site to the nourishment of the plant. The radical 

 fibrils, and the capillary roots impregnated witfi 

 moisture, will become so many electrical conduc- 

 tors, engaged in transmitting electricity, certainly 

 as necessary to lile as light and caloric. 



The merit of a theory is, that it accounts for 

 observed facts, enables us to foresee what will 

 take place under particular circumstances likely to 

 happen, and indicates the considerations which it 

 may be desirable to bring about with a view to 

 useful results. 



Let us inquire whether the theory now present- 

 ed, fulfils these conditions : 



Suppose a chalky soil. To improve it, we add 

 argillaceous marl ; i. e. to the lime which predo- 

 minates we add silica and alunn'na. Tu the posi- 

 tive element which loe found alone, we add the ne- 

 gative elements which we found deficient. 



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

 that the roots cannot penetrate it, or so split up 

 that water passes through it like a riddle, and that 

 the marling is simply designed to change this 

 physical condition?* 



But, if the object was merely to divide the 

 chalk, in order to change its physical condition, a 

 calcareous sand would accomplish this object, and 

 yet it never came into the head of an agricultur- 

 ist to improve his chalk by limestone, while Gor- 

 dan de Saint-Memin produced a magnificent ve- 

 getation 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 together. Conlraiy to Jiis expectations, the 

 sterility was increased. It was not till the fifth 

 year that the ground acquired a common degree 

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

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

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

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

 to vegetation, either by itselfj or in relijrence 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 

 relation to silica and alumina. Exposed to the 

 air, the combination is destroyed, the iron passes 

 to the stale of peroxide, susceptible of union with 

 silica and alumina. Yet, under such circum- 

 stances, it was not worth while to mingle the two 



G. Diet, d' Agriculture, aiticle Craie. 



