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THE FARMERS' REGISTER. 



doctrine ol' acid soils — which doctrine was set forth 

 still more at length in 1832, when that essay was 

 republished, and enlarged to a volunie. The doc- 

 trine was belbre that time not only unsupported by 

 auihorily, but utierly condemned t)y all that could 

 be considered as good euilioriiy. It wae advanced 

 by the author hesitaliniciy, becaus.e oi'his want ot' 

 the scientific attainments needed to pursue the 

 discovery, and to establish it by prool direct and 

 beyond dispute. And the asssertion was met, 

 by the lew men ol' science who condescended to 

 notice ii at all, by flat denial ol any acid int^te- 

 dienl exisiing in soil, or hy a jeering demand ol 

 the prool to be f'urnislied by exhibition ofthe sepa- 

 rated acid. 



But belore another edition Dplhat essay had 

 been issued (in 1^35) some ol the most distinguish- 

 ed European chemists had ascertained the now 

 generally conceded existence of an acid ingredi- 

 ent of soils in tfcneral, which was at tirst called 

 humic acid. And now there are as lew persons 

 who would deny or even doubt I iie existence ol'acid 

 in soil, as previously could have been Ibund to 

 give it credence on all the proof that could be ad- 

 duced. It would be even amusing to compare the 

 laborious indirect mode orproo('(lor want of direct 

 evidence) brought ai first to sustain the new posi- 

 tion, with the now universal aiimission of the 

 general existence ol humic acid, or some acid prin- 

 ciple, in soils. 



But, after all, it was not that a new constituent 

 part of soil was discovered in humic acid, or hu 

 mm, but that acid properties were Ibund in the 

 previously well-known ingredient, called by Davy 

 "vegetable extiac'," autl "humus" by earlier 

 French authors. This substance is the product of 

 vegetable matter decayinix in soil, and which ne- 

 cessarily must show as many shades of dilierence 

 of texture and condition as ihere are minute steps 

 in the progress of vegetat>le decomposition and 

 decay. The chemists, however, were delinhied 

 with the discovery, when announced in Europe 

 by Berzelius, Boullay, and oiher scientific names, 

 and hastened to make its lurther invesiigaiion. 

 Each gave a new name to every newly observed 

 difference ol condition, or chemical composition; 

 and the consequence is, that so many new names 

 have been applied, and as many different substan- 

 ces claimed to exist, that the whole subject is now 

 as much involved in the conlijsion of knovvlediie, 

 as belbre in ignorance. Thus, this substance, 

 known to and described by Davy as but one, ve- 

 getable extract, and considered by him as the di- 

 lect nutriment of planis, is now treated of under 

 many names, and each claimed to designate a 

 diffierent chemical sut)stance. Thus have been 

 brought into use, and used to obscure and confuse 

 rather than instruct, the terms humin and humic 

 acid, geine and geic acid, ulmin, coal of humus, 

 extract of humus, carbonaceous mould, apotheme, 

 crenic and apocrenic acids, &c. &c. We would 

 preler to go back to the older and more simple 

 nomenclature, and therefore approve of Liebig's. 

 He says — 



" The modifications of humus which are soluble in 

 alkalies are called humic add ; while those which are 

 insoluble have received the designations of humin and 

 coal of humus." (p. 57.) " Hiimus is described by 

 chemists as a brown substance, easily soluble in al- 

 kalies, but only slightly soluble in water, and produced 

 during the decomposition of vegetable matters by 

 the action of acids or alkaUes." — (p. 57.) 



The humin and humic acid produced by 

 chemical and by natural decomposition have the 

 same constituent pans, but varying much in pro- 

 portions; and thus even the same naine (many as 

 are the names) does not indicate the same chemi- 

 cal compound. 



" Humic acid formed by the action of hydrate of 

 potash upon saw-dust contains, according to the accu- 

 rate analysis of Peliicot, 72 per cent, of carbon, while 

 the humic acid obtained from turf and brown coal 

 contains, accordinir to Sprengel, only 58 per cent. ; 

 that produced by the action of dilute sulphuric acid 

 upon sugar, 57 per cent, according to Malaguti ; and 

 that, lastly, which is obtained irom sugar or from 

 starch, by means of muriatic acid, according to the 

 analysis of Stein, 64 per cent. All these analyses 

 have been repeated with care and accuracy, and the 

 proportion ot carbon in (he respective cases has been 

 ibund to agree with the estimates of the dilferent 

 chemists above mentioned; so that there is no reason 

 to ascribe the diiference in this respect between the 

 varieties of humus tu the mere difference in the me- 

 thods of analysis or degrees of expert ness of the 

 opera'tors." — (p. CO.) 



In a case where the most learned chemis's so 

 much differ and dispute, we shall not be so 

 presumptuous as to offer an opinion in competi- 

 tion. But, until they .<hall settle their differences 

 on this subject, and come to some general agree- 

 ment which may be considered as received 

 authoriiy, it may be permined to us, in common 

 Willi the unlearned, lo reject all these refinemenis. 

 VVeshall tlu'ielbre consider /tumus as vegetable 

 exitaci and decayinir matter </eiierally; and humin 

 as the less soluble, and humic acid as the more 

 soluble portion. 



Ail planis and vegetable [jroducts are compos- 

 ed principally of carbon, o.xytren and hydrogen ; 

 of a very small proportion of nitrogen, (or azote,) 

 and of small proporiions of earibs, alkalies, and 

 metallic oxides.* The firsi three, and bylarlhe 

 larger of ib.Hse constituents, are furnished in un- 

 liniiieif quantities bj' the atmnsfdiere ; that is, 

 carbon by the carbonic acid of the aimosphere, 

 and hydrogen and oxygen are the two consntuenis 

 of waier. Nitrosjen was not supposed until lately to 

 be a constiiuent of hut lew veiretable matters. But 

 now, and by Liebig, it is supposed to be univer- 

 sally present, though in very small proportions, 

 and to be essential 10 their existence. This con- 

 stituent is also furnished in profusion by the at- 

 mosphere, of which, nitrogen Ibrms 80 per cent. 

 It is then only the other very small constituents, 

 the earths, alkalies, and meiallic oxides, left in the 

 ashes of |)lants alter burninir, that are not furnished 

 by the atmosphere, and in unlimited quantity; and 

 these only must necessarily have been supplied to 

 growing plants ahoL'ether and directly by the soil 

 which the roots pervaded. 



* The most important and very far the larger con- 

 stituent parts of all plants, are furnished by or found in 

 the atmosphere, and are there, of course, in a gaseous 

 form, or presented as aeriform ff uids. Oxygen and ni- 

 trogen, two gases, in certain uniform proporiions, com- 

 pose the atmospheric air. Carbonic acid, a gas, and al- 

 ways present in small quantities in the atmosphere, is a 

 compound of carbon and oxygen. Hydrogen, which 

 when separate is known only in gaseous form, when 

 combined with oxygen forms water, which is held dis- 

 solved, and also as an aeriform fluid, when in the at- 

 mosphere. Ammonia, which Liebig consideis so im- 

 portant a supporter of vegetable growth, is also a gas, 

 and is a combination of nitrogen and hydrogen. 



