'n" 



THANSACTIONM OF SKfTION II. 



683 



organic 



rp.«iilt nf till' notion of nil oiyfuiiscd fcrnifiit, wliicli occurs nbnniliinfly in soils and 

 ill niii^t iin|iiiri' ■wutci-.s. Tlic cvidt'iice lor It'iinciit tlicorv nf nilritlciilioii i.s now 

 very cuiiiplutt'. Nitrilication in soils ani. waltTs ix fountl to lie slrictly liniilnl t<> 

 tlic viiiivi' nt' tcm]i((rafiin' \vitliin wliicli tlio \ital activity ol'Iiviufr IVnnoiits is cdn- 

 timd. 'i'liiis niti'iticatinii jiroci'iMJ.s will) cxInMiic slowness ni'jir tlic IVci'/injr-iioint, 

 ami inci'i'iisfs in jiclivity witli a lisc in li'ni|u'ratui'<' fill .'17' art! iciicliiiJ ; tlic uclioi) 

 tlii'iMliiuinislii's, and erases iiltoMTthcc nt !')'>, Nitriticuition is also dciu'iidi'iil on 

 till' jircsciici' of plant-l'ood siiitabli- for oiyniiisras of lowcliaractcr. Iicct'iit fxju'ri- 

 nunts at lli'thainsti'd show lliiit in tlif aiisi'iice of ]ilios]iliatt's no nitrilieiilion will 

 occiu'. J'"iirtlii'i' ]iidof of llic lorniciit thi'ory is aH'ordi'd liy tlif fact tluit aiiliscjitics 

 ail' fatal to nitriliciition. In tlio jiresi'iico of a small (|iiaiitity of cliloiiifonn, carlion 

 liisiiliiliidi', saiicylii! acid, and ii]i|iMn'iilly also ]ilii'nid, nilrilicalioii cnlii'dy ceases. 

 Till' action of lieat is ei|iially coiifimi.itory. IJaisini,' suwa^re to tlic lioiliiifi-jioint 

 cntitvly prevents its under^'oiiiij: nilriticalion. The lioatin;,' of soil to the sanio 

 ti'iiii>rnitiire etrectiially destroys its iiitiifyinu' ])ower. l'"iiially, nitrilication can ho 

 .started in hoiled sewajre, or in other sterilised linnid (d'siiitahle coniposition, hy the 

 addiii'iii of a few ])articles of fresh surface soil, or a low drops of a solution wliiidi 

 luis nlready nitrilied ; though without such addition those lif[iiids may lie freely 

 exposed to liltei'ed air withont nitrilication laiiiiii.' jilace. 



The nitrifyinf: orpinisni has lieeii subniitteil as yet to but little microscopical 

 study: it is aiijtareiitly a micrococc'us. 



It is dilliiMilt to conceive how the evidence for tho ferinent theory of nitrilica- 

 tion could bo I'lirther sireiie'tliened ; it is a])|)arent]y conipleto in every part. 

 Altliiiiijih, however, nearly the wliolo of tiiis evidence has lieen before the scientific 

 |mhlic i'or nioro than seven years, tho f'er'nent theory of nitrilication can hardly bo 

 said to have fibtained any fieiieral acceptance; it has not indeed been seriously con- 

 troveiled, but neither has it lieen embraced. It is )mrtly with the view of calling 

 the attention of lOnglish ami American (dieinists to the imjiortance of a decision on 

 this (lueslion that I have been induced to brinj,'- this subject before them on tho 

 present occasion. 



7'/ic Dintribufiiin of iho Xifrifi/i/ii/ Or<j(init<m in Ihe Soil. — Small quantities fif 

 soil were taken, at de])tlis varying IVoin two inches to eight feet, from freshly-cut 

 surfaces on the sides of ]iits sunk in tiie clay soil at l.'othamsted. The soil removed 

 was at once transferred to a .sterilised solution of diluted urine, which was after- 

 wards examineil from time to time to ascertain if nitrilication took place. From 

 the results it would apjieiir that in a clay soil the nitrifving oriranism is confined to 

 about eighteen inches from the surface ; it is most abundant in the tirst six inches. 

 It is (piite possible, however, that in the channels caused by worms, or by the roots 

 of plants, the organism may occur at greater depths. In a sandy soil wo should 

 expect to find the organism at a lower level than in clay, but of this wo have as yet 

 no direct evidence. 



Some very practical conclusions may be drawn from the facts now stated. It 

 appears that the oxidation of nitrogenous matter in soil will bo confined to matter 

 near the surface. The nitrates found in the subsoil, and in subsoil drainage waters,, 

 have really been produced in the upper layer of the soil, and have been carried down 

 by dilfusion, or by a descending column of water. Again, in an-anging a filter-bed 

 for the oxidation of sewage, it is obvious that with a heavy soil lying' in its natural 

 state of consolidation very little will be gained by making the filter-bed of con- 

 siderable depth ; while, if an artificial bed is to be const riu^ted, it is clearly the top- 

 soil, rich in oxidising organisms, which should bo exclusively employed. 



The. Substa7ices susceptible of Kitri/ication. — The analyses of soils and drainage 

 waters have taught us that the nitrogenous humic matter resulting from the decay 

 of plants is nitrifiable ; also that the various nitrogenous manures applied to land, as 

 farmyard manure, bones, fiah, blood, rape-cake, and ammonium salts, undergo 

 nitrification in the soil. In the Ilothamsted Laboratory experiments have been 

 made on the nitrification of solutions of various substances. Besides solutions con- 

 taining ammonium salts and urea, I have succeeded in nitrifying solutions of 

 asparagine, milk, and rape-cako. Thus, besides ammonia, two amides, and two 

 forms of albuminoids have been found susceptible of nitrilication. In all cases in 



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