THE EARTH. 29 



have for a long time supported men and other animals, having been 

 observed to become every day more barren ; while, on the contrary, 

 those desolate places, in which vegetables only are abundantly pro- 

 duced, are known to be possessed of amazing fertility. " In regions 

 which are uninhabited,"* says Mr. Buffon, " where the forests are not 

 cut down, and where animals do not feed upon the plants, the bed 

 of vegetable earth is constantly increasing. In all woods, and even 

 in those which are often cut, there is a layer of earth of six or eight 

 inches thick, which has been formed by the leaves, branches, and 

 bark, which fall and rot upon the ground. I have frequently observed 

 on a Roman way, which crosses Burgundy for a long extent, that there 

 is a bed of black earth, of more than a foot thick, gathered over the 

 stony pavement, on which several trees, of a very considerable size, 

 are supported. This I have found to be nothing else than an earth 

 formed by decayed leaves and branches, which have been converted 

 by time into a black soil. Now as vegetables draw much more of their 

 nourishment from the air and water than they do from the earth, it 

 must follow, that in rotting upon the ground, they must give more to 

 the soil than they have taken from it. Hence, therefore, in woods 

 kept a long time without cutting, the soil below increases to a con- 

 siderable depth ; and such we actually find the soil in those American 

 wilds, where the forests have been undisturbed for ages. But it is 

 otherwise where men and animals have long subsisted ; for as they 

 make a considerable consumption of wood and plants, both for firing 

 and other uses, they take more from the earth than they return to it ; 

 it follows, therefore, that the bed of vegetable earth, in an inhabited 

 country, must be always diminishing ; and must at length resemble 

 the soil of Arabia Petrea, and other provinces of the East, which 

 having been long inhabited, are now become plains of salt and sand ; 

 the fixed salt always remaining while the other volatile parts have 

 flown away." 



If from this external surface we descend deeper, and view the earth 

 cut perpendicularly downwards, either in the banks of great rivers, or 

 steepy sea-shores ; or, going still deeper, if we observe it in quarries 

 or mines, we shall find its layers regularly disposed in their proper 

 order. We must not expect, however, to find them of the same kind 

 or thickness in every place, as they differ in different soils and situa- 

 tions. Sometimes marl is seen to be over sand, and sometimes under 

 it. The most common disposition is, that under the first earth is found 

 gravel or sand, then clay or marl, then chalk or coal, marbles, ores, 

 sands, gravels, and thus an alternation of these substances, each grow- 

 ing more dense as it sinks deeper. The clay, for instance, found . at 

 the depth of a hundred feet, is usually more heavy than that found 

 not far from the surface. In a well which was dug at Amsterdam, to 

 the depth of two hundred and thirty feet, the following substances 

 were found in succession :t seven feet of vegetable earth, nine 

 of turf, nine of soft clay, eight of sand, four of earth, ten of clay, four 

 rf earth, ten of sand, two of clay, four of white sand, one of soft 

 earth, fourteen of sand, eight of clay mixed with sand, four of sea* 



Buffon, vJl. \ p. 353. t Varenius, as quoted by Mr. Buffon, p. 358. 



