196 QUESTION OF DURATION OF CALXING. 



is the cause requiring second and repeated applications of lime or 

 marl, as generally and erroneously supposed to operate, not only 

 Iby the ignorant, but by the scientific authorities whose opinions I 

 shall presently notice, and endeavour to controvert. 



So far, I have merely aimed to show, by facts and from experi- 

 ence, that the increased productiveness of soifs, induced by calca- 

 reous manures, has not ceased, nor, in general, been at all diminished 

 within such short time of experience as belongs to the agriculture 

 of this country, and of which only we can know and estimate all 

 the conditions and circumstances. But, however important may 

 be the value of these evidences of durable effect, bearing on the 

 question of the profit of practical operations, they go but little way 

 towards fixing the limit of duration, and of the undiminished ope- 

 ration of calcareous manures. 



In the first sketch of this essay, published in 1821, as well as in 

 all the subsequent editions, I asserted and argued for the absolute 

 permanency of calcareous earth, acting as manure in soil ; and the 

 remaining in the soil of the lime, with but very little appreciable 

 diminution of its quantity, through all its chemical changes and 

 different successive combinations. In this opinion I have found 

 myself opposed to nearly if not quite all known authorities, whether 

 of scientific writers, or the practical European cultivators whose 

 reported practices and results have been quoted as evidence. Under 

 such circumstances, it was proper that my grounds should be care- 

 fully reconsidered, in connexion with the opposing reasoning. This 

 has been done ; and while deeming it proper to yield something of 

 the breadth of my previous position to newer and better information, 

 and while ready to admit the previous errors, and their recent cor- 

 rection, I have still to maintain my former opinion in its most 

 important points. And, without exception, I deny the counter 

 opinions, either asserted by authors of high reputation, or neces- 

 sary deductions from, their assertions, viz. : that calcareous manures, 

 though long continuing in soils, still are liable to be nearly exhausted 

 by waste and use in terms of say twenty or thirty years ; and that 

 they then require being replaced, and may be so repeated, profitably, 

 and without limitation of the number. 



No calcareous manurings made by man can possibly be old enough, 

 or capable of being clearly enough traced through their actual pro- 

 gress, to afford evidence of even very long duration, much less en- 

 tire permanency of effect. But, however weak for this purpose, 

 such facts, of long abiding effects, will at least serve to rebut the 

 assertions of the much earlier and necessary cessation of all the 

 effects of lime. For such opposition even my own experience of un- 

 abated effects, from applications not repeated, now extends to thirty- 

 one years. Another much older application (stated at page 114), 

 after long neglect, and under the worst treatment for its operation, 



