CALCAREOUS MANURES-APPENDIX. 243 



Just before this time Davy's « Agricultural Chemistry' had been published 

 in this country ; and I read it with delight, notwithstanding my then total 

 ignorance of chemical science, and even of chemical names, except as 

 learned by tliat perusal. There was one passage of this author which seemed 

 to promise to afford both light and hope on the point in which disappoint- 

 ment had led me to despair. As an illustration of defects in the chemical 

 constitution of soils, and of the remedies which proper investigation might 

 point out, he adduced the fact of a soil "of good apparent texture," which 

 was sterile, and seemed incapable of being enriched. The fact which struck 

 so forcibly on my mind was presented in the following concise passage of 

 Lect. iv. "If on washing [for analyzing] a sterile soil, it is found to contain 

 the salt of iron, or any acid matter, it may be ameliorated by the applica- 

 tion of quick-lime. A soil of good apparent texture from Lincolnshire, was 

 put into my hands by Sir Joseph Banks as remarkable for sterility. Cn 

 examining it, I found that it contained sulphate of iron ; and I offered the 

 obvious remedy of top-dressing with lime, which converts the sulphate into 

 a manure." 



Much the greater part of my land, and of all the land of lower Virginia, 

 seemed to me just such as Davy descried in this single and peculiar soil. 

 It was certainly of " good apparent texture," that is, it was neither much 

 too clayey or too sandy, nor had it any other apparent defect to forbid its 

 being fertile in a very high degree. Yet it was and always had been sterile, 

 and, as my experience now concurred with that of my older friend in show- 

 ing, it could not be either durably or profitably enriched by putrescent ma- 

 nures. Could it be possible that the sulphate of iron (copperas) which Davy 

 found in this soil, and which he evidently spoke of as a rare example of pe. 

 culiar constitution, could exist in nineteen twentieths of all the lands of 

 lower Virginia] This could scarcely be; and yet, in despair of finding other 

 causes, I set about searching for this one. 



It was not difficult, even for a reader so little instructed in chemistry, to 

 apply the test for copperas. It was only necessary to let a specimen of the 

 suspected soil remain soaking in pure water, until any copperas, if present, 

 would be dissolved; then to separate the fluid by pouring off and filtra- 

 tion, and then to add to the fluid some of the infusion of nut galls. If 

 copperas had been held in solution, the mixture would produce a true ink, 

 of which the smallest proportion would be made visible in the before per- 

 fectly transparent water. But all these first attempts were fruitless, and I 

 was obliged to conclude that the great defect, or impediment to improve- 

 ment, in most of our soils, was not the presence of the salts of iron. But 

 though not a salt, of which one of the component parts was an acid, might 

 not the poisonous quality be a pure or xincomhined acid? This question 

 was raised in my mind, and the readiness produced to suppose the affirma- 

 tive to be true, by several circumstances. These were, 1st, that certain 

 plants known to contain acid, as sheep-sorrel and pine, preferred these soils, 

 and indeed were almost confined to them, and grew there with luxuriance 

 and vigor proportioned to the unfitness of the land for producing cultivated 

 crops. 2nd. That of all the soils supposed to be acid which I examined by 

 chemical tests, not one contained any calcareous earth.* 3rd. That the 

 small proportion of my land, and of all within the range of my observation, 



* I was not thon aware, of the important and novel fact which I afterwards ascertained 

 and established, and which is now fully received (with very slia;ht acknowledgment 

 of its source) by the geologists of this country, that almost all the soils on the Atlantic 

 slope of this country, and even including nearly all limestone soils, are also entirely de- 

 stitute of carbonate of lime, though that ingredient seems nearly if not quite universal in 

 all the good soils of England and the continent of Europe. 



