214 



F A K M E R S ' REGISTER, 



rNo. 4 



10 Grammes gave: 



Silex - - - 1.80 

 Alumina - - - 0.20 

 Carbonate of lime - - 0.90 

 Sub-carbonate ol" magnesia - 0.47 

 Oxide of iron - - 0.27 

 Oxide de magnesie*^ [manga- 

 nese?] a trace - - 0.00 

 Water - - - 0.20 

 Humus, soluble - - 0.05 

 Loss, and charcoal of insolu- 

 ble humus - - 0.11 



10.00 



This earth, the least fertile of all those analyzed, 

 contains twice as much carbonate ol' lime and of 

 mao^nesia as the former; the color also is whiter. 

 It appears to receive its change of color I'rom the 

 detritus (or broken down fragments) of the friable 

 rock on which it is based; its composition is almost 

 identical with that ol' the sub-soil No. 4, of which 

 we shall give the analysis below. 



No. 3. Sandy eartli of the calcareous plain be- 

 longing to those portions of the plain, which, in 

 the revolution that carried off the silicia-argila- 

 ceous stratum, preserved a part of it now mixed 

 with the soil of the plain. 



10 grammes of this earth contain: 



Silex - - - - - 7.90 

 Aluminc . _ - - 0.67 

 Sub-carbonate of lime (rep- 

 resented by c/iZar»rc, 0.18) - 0.16 

 Sub-carbonate of magnesia - 0.02 

 Oxide of iron _ - - 0.47 

 Oxide de magaesic* [manga- 

 nese?] . - . _ 0.03 

 Humus, soluble . _ . 0.15 

 Water - - - - 0.35 

 Loss and charcoal of insolu- 

 ble Humus - - - - 0.25 



10.00 



This earth presents a great difference in com- 

 position from the preceding, since it contains SO 

 per cent of silex and scarcely 16 thousandths of 

 carbonate of lime, and 2 thousandths of carbonate 

 of magnesia. Yet its properties, its productions 

 and its defects, are nearly the same as those of the 

 preceding numbers. On the other hand, it would 

 seem by its composition to be almost confounded 

 with the sandy sub-soils of the plateau lying on 

 the other side of the valley; but it produces nei- 

 their heath, broom, nor sheep sorrel, &e.; plants 

 characterizing these sands — and it agrees, as to 

 cultivation; with Nos. 1, and 2, and hke them, 

 spontaneously produces euphorblia, thistles and 

 other plants useless to cattle. It possesses then 

 those common properties of an active agent which 

 must be common to both, which makes them a 

 distinct class; and this agent can be nothing else 

 than the mixture, or |)erhaps combination of the 

 carbonates of lime and magnesia. 



These two ))rinciplcs, therefore, have a very 

 great effect upon vegetation, since 16 thousandths 

 of carbonate of lime joined to 2 thousandths of 

 carbonate of magnesia are sufficient to change 

 entirely the nature and products of the soil. But 



let us pursue our analyses before making a deduc- 

 tion of all their consequences. 



No. 4. Sub-soil of the plain. Its color is red- 

 dish, as is that of many calcareous soils of good 

 quality; but having been neither affected nor mod- 

 ified by the waters of the last revolution, in con- 

 sequence of the shelter given it by the upper stra- 

 tum; ami not having been exposed to the atmos- 

 pheric influences, it may be regarded as the type 

 of the deposite which "forms the soil of the plain, 

 the deposite anterior to the silicio-argilaceous for- 

 mation. 



10 Grammes of the sub-soil of the plain gave: 



Silex 



Alumine - . _ 



Carbonate of lime (repre- 

 sented by chlorurc, 8.20) 

 Carbonate of magnesia - 

 Oxide of iron 

 Oxide of magnesia 

 Water - " - 

 Humus, soluble 

 Loss - _ _ _ 



0.39 

 1.27 



10.00 



♦ So in the original. — Ed. 



This soil is a species of marl which contains 74 

 per cent of carbonate of lime, 4 ol" magnesia and 

 12 per cent of alumine: its composition is quite 

 similar to that of the analysed soils of the plain. 



III. These analyses may afford us important 

 inferences. 



These soils evidently make, as we have seen, a 

 distinct class of the .silicious soils. Their proper- 

 ties seem to differ at least as much from those of 

 calcareous soils, properly so called, which pro- 

 duced spontaneously the small sppcies of clover, 

 on which leguminous plants of different species 

 succeed easily, and manures a'most always se- 

 cure good crops. It is not then to the carbonate 

 of lime that they owe their inferiority: its action, 

 on the contrary seems, to be nullified, since the 

 characteristic properties of calcareous soils appear 

 no longer to exist in these. Nor is it more to the 

 silex, the alumine, nor the oxide of iron, which 

 are I'ound in abundance in all good soils, that this 

 difference can be atmbuted. Then, of all their 

 constituents, there remains only the magnesia to 

 which can be owing the characters which distin- 

 guish them from their analogous soils. 



It has been already fully admitted in principle 

 that magnesia is unfavorable to veselalion. The 

 English chemist Tennant formed tliis conclusion 

 from the analysis of a lime which struck with 

 sterility all the soils to which it was applied. In 

 America the use of a magnesian lime quickly 

 wore out (fdtigne) the soil; and Davy has admit- 

 ted it as a truth. Some trials on a small scale have 

 shown me that while in a calcareous soil, beans, 

 when sown, sprouted soon, and came up vigorous- 

 ly, in the same soil modified by an addition of 

 magnesia, germination was refardeded, and the 

 stalks especially had only a feeble and lardy 

 growth: Yet That'Tcall into question the soil being 

 made steril by magnesia; and opposes to the con- 

 clusions of Tennant, that lOinhoif has analyzed a 

 very fertilizing marl which contained 20 per cent 

 of magnesia: and farther, it results from a careful 

 analysis, that the mud of the Nile, which we know 

 to be so fertile, contains a large proportion of mag- 

 nesia. From these last facts it mav be concluded 



