CALCAREOUS MANURES-APPENDIX. 173 



nutritive principles contained in the soil, and if these are not in the soil, 

 the flower falls without forming any fruit. The experiments to which 

 Th. de Saussure has submitted soil, [terre vegetale] appear to demonstrate 

 that the three constituent principles of mould may be converted the one 

 to the other, under the alternately preponderating influence of air and 

 water. Water converts to the extract of mould a part of the insoluble 

 geine contained in the soil, and this transformation extends more and more, 

 so that finally the greater part of the geine becomes soluble. In contact 

 with the air, the dissolved matter passes again to the state of geine. The 

 carbonaceous mould which changes a part of the air into carbonic acid, is 

 itself changed by air into geine and into extract of mould, and it is upon 

 this transformation that appear to depend in part the advantages derived 

 from the tillage of the soil, which is divided by the action of the plough, 

 and exposed to the immediate influence of the air. In this manner all the 

 parts of the soil contribute to nutrition ; Vhilst it is probable that the solu- 

 tion of the extract of mould, that of the geate of lime, and perhaps also 

 that of the geate of alumine, are immediately absorbed by the roots. During 

 a heavy rain, this solution penetrates tlie interior, and often to very deep 

 beds of the sterile earth ; but notwithstanding that, it is not lost to vegetable 

 life ; for the roots of trees seek it, and bring it back as matter suitable 

 for their nourishment. 



Experience has demonstrated that quick-lime and the carbonate of lime 

 mingled with the soil, favor the vegetation produced thereon. Chemistry 

 has not yet explained, in a satisfactory manner, the power which lime thus 

 exerts; however, it is known that when the soil contains this alkaline 

 earth, or, in its place, ashes only, the mould is quickly consumed, and vege- 

 tation becomes more rich in proportion. It has thence been concluded 

 that lime acts, partly in exciting the plant to greater activity, and partly in 

 rendering more soluble the principles of the soil, which are absorbed by 

 the roots when dissolved in the water which the earth has imbibed. Lime 

 is not then a true [or alimentary] manure. It contributes only to pro- 

 mote and hasten the absorption of the principles which serve to nourish 

 the plant ; and that lime may be serviceable, it is necessary to introduce 

 into the soil improved by lime, materials proper to furnish new quantities 

 of mould. The lime or alkali contained in ashes acts also in hastening 

 the change of organic matters to mould. 



It is known by experience, that gypsum also augments the fertility of the 

 earth, especially when leguminous plants are cultivated. It is not probable 

 that this neutral salt acts in the same manner as Hmc, and we are ignorant 

 of what is its mode of acting. 



Soil {terre vegetale] possesses the property of being able to retain as 

 much as three-fourths of its weight of water without appearing moist, and, 

 like charcoal, it condenses atmospheric humidity. It owes tliis property to 

 the geine which it contains, which is one of the substances that, of all 

 known, absorbs moisture with most energy. Mould [terreau] can absorb 

 double its weight of water, without appearing moist ; and after being 

 dried, it draws from the air, in less than twenty-four hours, a quantity of 

 water, which may vary according to the humidity of the atmosphere, from 

 80 to 100 per cent, of its weight. This property depends upon its light 

 and dust-like consistence ; and geine, of which the fracture becomes vi- 

 treous from its course of chemical treatment, is deprived of this physical 

 property, which is of the utmost importance to vegetable life. For, in con- 

 sequence of this property, mould retains water in the earth and obstructs 

 its evaporation ; and it is probably this water which maintains the extre- 

 mities of the roots in the state to perform their functions. 



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