NEUTRAL SOILS. 77 



neutralized, to borrow a figure from my subject)^ by showing that 

 an equal difficulty awaits those who may support the other side of 

 the argument. 



The theory of geologists of the formation of soils, from the de- 

 composition or disintegration of rocks, is received as true by all 

 scientific agriculturists. The soils thus supposed to be formed, re- 

 ceive admixtures from each other, by means of different operations 

 of nature, and after being more or less enriched by the decay of 

 their own vegetable products, make the endless variety of existing 

 soils.* But where a soil, lying on and thus supposed to have been 

 formed from any particular kind of rock, is so situated that it could 

 not have been moved, nor received considerable accessions from 

 torrents or other agents, then, according to this theory, the rock 

 and the soil should be composed of the same materials ; and such 

 soils as the specimens, marked 11 and 16 (page 64), would be, like 

 the rock they touched, nearly pure calcareous earth, instead of be- 

 ing (as they were in truth) destitute, or nearly so, of that ingre- 

 dient. Such are the doctrines received and taught by Davy, or the 

 unavoidable deductions from them. But, without contending for 

 the full extent of this theory of the formation of soils, every one 

 must admit that soils thus situated must have received, in the lapse 

 of ages, some accessions to their bulk, from the effects of frost, 

 rain, sun, and air, on the lime-stone in contact with them. All 

 lime-stone soils, properly so called, exhibit certain marked and pe- 

 culiar characters of colour, texture, and products, which can only 

 be derived from receiving into their composition more or less of the 

 rock which lies beneath, or rises above their surface. This mixture 

 will not be denied by any one who has observed lime-stone soils, 

 and reasons fairly, whether his investigation begins with the causes, 

 or their effects. If then all this accession of carbonate of lime re- 

 mains in the soil, why is it that none, or almost none, is discovered 

 by accurate chemical analysis ? Or, if it be supposed not present, 

 nor yet changed in its chemical character, in what possible manner 

 could a ponderous and insoluble earth have made its escape from 

 the soil ? To remove this obstacle, without admitting the opera- 

 tion of acid in making such soils neutral, will be attended with at 

 least as much difficulty, as any arising from that admission being made. 



7th. But we are not left entirely to conjecture that soils were 

 once more calcareous than they now are, if chemical tests can be 

 relied on to furnish proof. Acid soils that have received large 

 quantities of calcareous earth as manure, after some time, will yield 

 very little when analyzed. To a soil of this kind, full of vegetable 

 matter, I applied, in 1818 and 1821, fossil shells at such a known 



* Agr. Cliem. p. 131. Also Treatise on Agriculture (by General Arm- 

 strong), quoted in a preceding page (53) of this essay. 



