204 



FARMERS' REGISTER. 



[No. 4 



The art^ilo-silicious soil, on the contrary, be- 

 longs, as we shall see hereailer, to a great deposite 

 which seems to have been general; but which, 

 however, did not rise to great heights. It covers, 

 in France and elsewhere, vast extents, and it com- 

 poses at least three fourths of our tbrest lands in 

 ihe plains; the great Ibrcsts in the neighborhood ol 

 Paris anil those of Normandy are almost entirely 

 com posed of it. It is the only great shade of soil 

 which is produced every where with striking an- 

 alogies in its soil, its sub-soil, its properties, its ad-_ 

 varTtages and its defects; while other natures of 

 soil ofler great disparities among themselves in 

 the different positions in which they occur. 



Its composition, in the first place, as we have 

 previously announced, is completely identical, but 

 it varies much in consistence, and in the taculty 

 of retaining water, according to the greater or less 

 quantity ol" clay which it contains, and as the si- 

 licious sand found m it is in a state of more or less 

 minute division; for the experiments of Thacr, 

 Schubler, and Cadet Gaussicourt, have proved 

 that the stiffness of a soil and its impermeability 

 (impenetrability to water) depend on the minute- 

 ness of division of the silex, as well as on the 

 proportion of clay that it contains. Silex in the 

 form of coarse sand takes only one fourth of its 

 weight ol" water, while reduced to an impalpable 

 powder, euch a» is obtained Irom clay, it retains 

 nearly three times its weight; which explains, on 

 the one hand, the great humidity of argillaceous 

 soils and on the other the great contraction that 

 clay suffers either by drought in agriculture, or by 

 heat in the arts. 



li. The color of the surface of this soil, when 

 it lias been long exposed to the air, is white, which 

 has given use to its name of white lahd, (terre 

 blanche, terrain blanc.) 



What characterises this soil particularly is that 

 when it is dry, it is easily enough penetrated by 

 water, but when once saturated, it admits no 

 more; the water which then falls upon its surface 

 remains there without being able to penetrate it; 

 this property has caused it to be called impermea- 

 ble soil, because in fact it does not permit the water 

 to pass through to the lower strata. 



One of the worst results of this impermeability 

 of the soil is the unhealthiness which is experienced 

 in a greater or less degree wherever this soil oc- 

 curs: the intermittent levers wliich are observed 

 more or less on the borders of stagnant waters are 

 very frequently endemic on the argilo-silicious 

 plains, although they may present neither marshes 

 nor ponds. 



This unhealthiness, it appears, may be explained 

 in a plausible manner. 



The water with which (he soil is inundated, not 

 being able to escape in any direction, remains 

 there in a state of stagnation, the general principle 

 of the corruption of water. It forms then in the 

 soil a kind of interior marsh; the sun and the dry- 

 ness of the air exhale a part. Tliese waters, mo- 

 tionless, diminished, heated by the sun in the 

 warmth of the long summer's days, ferment, he- 

 come altered, and are sometimes so much corrupt- 

 ed as to become black; they are then an unwhole- 

 some drink for men; and at the same time the ex- 

 halations of a soil impregnated vvith corrupted wa- 

 ter become unhealthy, as those of the borders of 

 marshee, of ponds, and of all lands temporarily 

 inundated, and which the summer's sun strikes 



upon, after the waters are drawn off. Then among 

 the inhabitants of a district, in the midst of an at- 

 mosphere mixed whh deleterious exhalations, nu- 

 merous intermittent levers occur, without any ne- 

 ces.sity Ibr the appearance of marshes or ponds in 

 the country, 



III. Almostalwaj'sunder the white [or light co- 

 lored] upper soil, a sub-soil is found of clayey sand 

 {sable argileux) reddish and shaded with gray, or 

 more rarely with red veins. 



Its color may enable us to form a judgment of its 

 degree of impermeability, and consequently of the 

 degree of humidity of its surface: when the whole 

 mass, soil and sub-sod, is gray, it is more imper- 

 meable, and its upper stratum is more wet: when 

 the inferior stratum is reddish or veined, the soil 

 allows the surface water to penetrate a little more, 

 and the upper layer is better drained; it is then re- 

 markable that the gray veins which it contains 

 are more moist than the rest of the mass. The 

 gray color, doubtless arises from the greater abun- 

 dance of clay, and the red announces a greater 

 proportion ot sand, colored by the oxide of iron. 



Nevertheless in all its varieties, this stratum re- 

 tains the water on its surface in a greater or less 

 degree, and allows scarcely any to penetrate into 

 the interior of the soil. 



IV. The argilo-silicious formation covers vast 

 extents of the two grand divisions of which France 

 is composed, the basin of the Mediterranean, and 

 that of the ocean. In these two positions, so differ- 

 ent, although near, we are unable to assign to the de- 

 posites of this stratum shades of difference which 

 may very sensibly distinguish them. That which 

 covers a part of the basin ot the Rhone, the only 

 basin of France which declines towards the Me- 

 diterranean, presents, then the same characteris- 

 tics as m the other parts of this country which de- 

 cline towards the ocean. Nevertheless, in the ba- 

 sin of the Rhone, the alluvion may be more clay- 

 ey, a property which it shares with all the diffier- 

 ent strata of the surface of the soil in this ba- 

 sin. 



The cause of this may be attributed to the nu- 

 merous fiirmations of gray clay, which we shall 

 call granitic clay, that are found in this basin; and 

 besides, to this circumstance, that the river which 

 occupies the bottom of this basin having a mucii 

 greater descent than those which ffow to the 

 the ocean, (since Geneva is 300 toises above the 

 level of the sea, consequently in a course of 120 

 leagues the river fiills 300 toises,) the soil there 

 has been more profoundly agitated, the plastic clay 

 has been dissolved in greater masses, and has given 

 more stithiess to all tliese strata of the basin, and 

 first to the argilo-silicious formation. 



V. This formation, generally, covers the pla- 

 teaux, [ridges, or table lands] which separate the 

 basins of great rivers, whenever they are not di- 

 vided by elevated mountains; and when moun- 

 tains divide them, this formation often rises 

 on their slopes to very considerable height.-'. 

 Thus it is found on the first steps, or as- 

 cent, of the mountains of Autumnois; it is 

 found covering the granites of a part of Haut- 

 Charolais, of the mountains of Forez, and rising 

 to almost equal heights on the two slojjes of those 

 mountains which decline, on the one side to the 

 Loire, and on the other to the Rhone — that is to 

 say, to the ocean and to the Medeitcrranean. But 

 then the difference of stiflhess is sensible between 



