PREFACE TO THE FIFTH EDITION. V 



connected therewith, had any bearing on my claim which is of 

 showing why, and under what circumstances, calcareous manures 

 are especially and generally necessary in this country, and of in- 

 ducing the extensive use of the particular material above named, 

 of which the existence had before attracted the notice of but few 

 persons, and of which any value was suspected by still fewer and 

 the few earlier trials of which had been altogether empirical, and 

 made without any knowledge of the mode of operation and which 

 therefore had generally ended in supposed failure and certain dis- 

 appointment, and speedy abandonment of all further effort. 



As to the opinions above enumerated, which served to direct 

 my practice from the beginning of 1818, they had either no sup- 

 port from previous authority, or, if asserted by any, had been 

 denied by higher authority and by general understanding. This 

 latter case, of feeble assertion and stronger denial, covers only the 

 doctrine of acid in soils. The other important positions had not 

 been asserted by any known authority, previous to my declaration. 

 Yet all these doctrines are now received either generally or uni- 

 versally, and so appear in recent publications on scientific agricul- 

 ture. And in regard to the existence of acid in soil, the actual 

 discovery was truly made in Europe, later, indeed, than my first 

 annunciation of the doctrine, by men of high scientific attainments, 

 who most probably had never even heard of the opinions of so 

 remote and obscure a writer as myself. 



Under these circumstances, when these now generally received 

 opinions are seen stated in any of my former editions (and still more 

 if in a subsequent edition), such appearance would not necessarily 

 imply the originality of such opinions. For it might well be 

 inferred by the (otherwise well-informed) reader, that these doc- 

 trines had been introduced in the later editions, after they had 

 been discovered and published by other authorities. For it is the 

 general and proper usage of authors of scientific and didactic 

 works, to add to each successive edition any new lights on the 

 subject, up to the latest time of publication. Hence, when dates 

 and authorities are omitted (in regard to doctrines long established 

 and received), it is left doubtful which of the positions of an 

 author's latest edition had also been maintained in his earliest ; 

 and also, whether such doctrines were original with the author 

 then stating them, or belonged to some other discoverer not then 

 cited. It is especially designed, in this last edition, to avoid every 

 such source of error. For this purpose, the Chapters (from II. to 

 VIII. inclusive) which will set forth all these theoretical doctrines, 

 will exhibit an exact reprint of the edition of 1832. No altera- 

 tions of the original text will be made, other than merely verbal 

 and immaterial corrections. Any new matter, or extension of 

 remark or illustration, will be designated in every case; and, 

 1* 



