378 LIME ALWAYS PRESENT IN FERTILE SOILS. 



experience. I shall presently have an opportunity of directing your 

 attention to the two concurring causes by the joint operation of which 

 lime is sooner or later wholly removed from the soil, even where, as in 

 the Wolds, it rests immediately upon the cJjalk. 



§ 8. /^ lime indispensable to the fertility of the soil 1 



It is the result of universal experience wherever agriculture has been 

 advanced to the state of an art, that the presence of lime is useful to 

 the soil. 



Not only is this fact deduced from the result of innumerable applica- 

 tions of this substance (o lands of every quality, but it is established 

 also by a consideration of the known chemical constitution of soils 

 which are naturally possessed of unlike degrees of fertility. 



Thus sandy or siliceous soils are more or less barren if lime be ab- 

 sent — while the addition of this substance in (he form of marl or other- 

 wise renders them susceptible of cultivation. So clay soils, in which 

 no lime can be detected, are often at once changed in character by a 

 sufficient liming. Felspar soils contain no lime, and they are barren— 

 and the same is true of such as are derived immediately from the de- 

 gradation of the serpentine rocks. 



Trap soils, on the other hand — such as are derived from decayed 

 basalts or green-stones — are poor in proportion as felspar abounds in 

 them. Where augites and zeolites are present in large proportion in 

 the trap from which they are formed, the soils are rich, and may even 

 be used as marl. The only difference in this latter case is, that lime is 

 not deficient (Lee. XIT., § 4), — and to this difference the greater fertility 

 iviay fairly be ascribed. 



But let it be conceded that lime is useful to or benefits the soil in 

 whicli it exists, you may still ask — is lime indispensable to the soil ? — 

 is it impossible for even an average fertility to be manifested where 

 lime is entirely absent ? 



There are two different considerations, from each of which we may 

 deduce a more or less satisfactory answer to this question. 



1°. The resHlt of all the analyses hitherto made of soils naturally 

 fertile show that lime is universally present. The per-centage of lime 

 in a soil may be very small, yet it can always be detected when valua- 

 ble and healthy crops will grow upon it. Thus the fertile soil of the 



Marsh lands in Hoistein contains 0-2 per cent, of carbonate of lime. 



Salt marsh in East Friesland 0*6 " *' 



Rich pasture near Durham . 1*31 " " 



But though the per centage of lime in these cases appears small, the 

 absolute quantity of lime present in the land is still large. Thus sup- 

 pose the first of these soils, which contains the least, to be only six 

 inches in depth, and each cubic foot to weigh only 80 lbs. — it would 

 contain about 3500 lbs. of carbonate of lime, upwards of a ton and a 

 half, in every acre. And this lime would be intimately mixed with the 

 whole soil, in which state it is always mosr effective in its operation. S' 

 may also be inferred with safety, that if the upper six inches containei 

 this proportion of lime, the under soil would probably be richer still, 

 since lime tends not so much to diffuse itself through, as to sink down- 

 wards into the soil. 



