644 



NA TURE 



[Oct. 30, 1884 



it lies within a few miles of the path of the greater part of the 

 trade of Europe with the Far East — than any previous traveller. 

 The apparently interminable war between the Dutch and the 

 natives of Sumatra renders travelling or investigation in that 

 marvellous island all but impossible to Europeans. 



At a meeting of the Society for Commercial Geography o' 

 Paris, held on the 21st inst. under the presidency of M. Meurand, 

 Dr. Neis, of the Naval Medical Service, recounted the incidents 

 of a recent journey from Saigon to the frontiers of Tonquin, 

 and thence to Bangkok. He travelled from the basin of the 

 Meikong to that of the Meinam, and referred in his paper to the 

 various tribes met on the frontiers of Tonquin and Cambodia, 

 and to the progress of England in Siam and Burmah. The 

 Society, we observe, now numbers 1000 members. 



The following is a list of the papers arranged to be read before 

 the Society for Commercial Geography of Oporto during the 

 ensuing winter session : — Useful animals of Portugal and its 

 possessions, by M. Torgo, jun. ; crime from climatological and 

 ethnological points of view, by M. Veloso ; the geography of 

 the Azores, by M. Silva ; the exportation of national products 

 to Brazil and the Portuguese colonies, by M. Gonsalvez ; the 

 climatological geography of the Portuguese colonies, by M. 

 Monteira ; recent colonial treaties with England, by M. de 

 Sonza. 



Petermanri s Mittheilungen for October contains an article on 

 the south-western portion of the province of Ciudad-Real, in 

 Spain, with a map, by Herr Otto Neussel ; one by Dr. Roukis, 

 on the ethnography and statistics of Albania, based on a series 

 of articles contributed to the Athens journal Akropolis, under 

 the title of " The Present and the Future of Albania," by the 

 late Greek Consul-General in that country ; a third paper on 

 Terek is a translation of one read before the Caucasian section 

 of the Russian Geographical Society by Herr Dinnik. The 

 " Recent Information from Corea " is that published in English 

 Blue-books as reports from various consular officials who have 

 lately visited the peninsula. 



NOTES ON NITRIFICATION^ 

 TN the following brief notes I propose to consider in the first 

 place the present position of the theory of nitrification, 

 and next to give a short account of the results of some recent 

 experiments conducted in the Rothamsted Laboratory. 



The Theory of Nitrification. — The production of nitrates in 

 soils, and in waters contaminated with sewage, are facts tho- 

 roughly familiar to chemists. It is also well known that ammo- 

 nia, and various nitrogenous organic matters, are the materials 

 from which the nitric acid is produced. Till the commencement 

 of 1877 it was generally supposed that this formation of nitrates 

 from ammonia or nitrogenous organic matter was the result of 

 simple oxidation by the atmosphere. In the case of soil it was 

 imagined that the action of the atmosphere was intensified by 

 the condensation of oxygen in the pores of the soil ; in the case 

 of waters no such assumption was possible. This theory was 

 most unsatisfactory, as neither solutions of pure ammonia, or of 

 any of its salts, could be nitrified in the laboratory by simple 

 exposure to air. The assumed co idensation of oxygen in the 

 pores of the soil al-o proved to be a fiction as soon as it was 

 put by Schlcesing to the test of experiment. 



Early in 1877, two French chemists, Messrs. Schlcesing and 

 Miintz, published preliminary experiments showing that nitrifi- 

 cation in sewage and in soils is the result of the action of an 

 organised ferment, which occurs abundantly in soils and in most 

 impure waters. This entirely new view of the process of nitri- 

 fication has been amply confirmed both by the later experiments 

 of Schlcesing and Miintz, and by the investigations of other 

 chemists, amongst which are those by myself conducted in the 

 Rothamsted Laborat ry. 



The evidence for the ferment theory of nitrification is now 

 very complete. Nitrification in soils and waters is found to be 

 strictly limited to the range of temperature within which the 

 vital activity of living ferments i^ confined. Thus nitrification 

 proceeds with extreme slowness near the freezing-point, and 

 increases in activity with a rise in temperature till 37° are 

 reached ; the action then diminishes, and ceases altogether at 

 55°. Nitrification is also dependent on the presence of plant- 



food suitable for organisms of low character. Recent experi- 

 ments at Rothamsted show that in the ab-ence of phosphates 

 no nitrification will occur. Further proof of the ferment theory 

 is afforded by the fact that antiseptics are fatal to nitrification. 

 In the presence of a small quantity of chloroform, carbon bisul- 

 phide, salicylic acid, and apparently also phenol, nitrification 

 entirely ceases. The action of heat is equally confirmatory. 

 Raising sewage to the boiling-point entirely prevents its under- 

 going nitrification. The heating of soil to the same temperature 

 effectually destroys its nitrifying power. Finally, nitrification 

 can be started in boiled sewage, or in other sterilised liquid of 

 suitable composition, by the addition of a few particles of fresh 

 surface soil, or a few drops of a solution which has already 

 nitrified ; though without such addition these liquids may be 

 freely exposed to filtered air without nitrification taking place. 



The nitrifying organism has been submitted as yet to but little 

 microscopical study : it is apparently a micrococcus. 



It is difficult to conceive how the evidence for the ferment 

 theory of nitrification could be further strengthened ; it is ap- 

 parently complete in every part. Although, however, nearly 

 the whole of this evidence has been before the scientific public 

 for more than seven years, the ferment theory of nitrification 

 can hardly be said to have obtained any general acceptance ; it 

 has not indeed been seriously controverted, but neither has it 

 been embraced. In hardly a single manual of chemistry is the 

 production of saltpetre attributed to the action of a living fer- 

 ment existing in the soil. Still more striking is the absence of 

 any recognition of the evidence just mentioned when we turn to 

 the literature and to the public discussions on the subjects of 

 sewage, the pollution of river water, and other sanitary ques- 

 tions. The oxidation of the nitrogenous organic matter of river 

 water is still spoken of by some as determined by mere contact 

 with atmospheric oxygen, and the agitation of the water with air 

 as a certain means of effecting oxidation ; while by others the 

 oxidation of nitrogenous organic matter in a river is denied, 

 simply because free contact with air is not alone sufficient to 

 produce oxidation. How much light would immediately be 

 thrown on such questions if it were recognised that the oxidation 

 of organic matter in our rivers is determined solely by the 

 agency of life, is strictly limited to those conditions within which 

 life is possible, and is most active in those circumstances in 

 which life is most vigorous. It is surely most important that 

 scientific men should make up their minds as to the real nature 

 of those processes of oxidation of which nitrification is an 

 example. If the ferment theory he doubted, let further experi- 

 ments be made to test it, but let chemists no longer go on 

 ignoring the weighty evidence which has been laid before them. 

 It is partly with the view of calling the attention of English and 

 American chemists to the importance of a decision on this ques- 

 tion that I have been induced to bring this subject before them 

 on the present occasion. I need hardly add that such results as 

 the nitrification of sewage by passing it through sand, or the 

 nitrification of dilute solutions of blood prepared without special 

 precaution, are no evidence whatever against the ferment theory 

 of nitrification. If it is to be shown that nitrification will occur 

 in the absence of any ferment, it is clear that all ferments must 

 be rigidly excluded during the experiments ; the solutions must 

 be sterilised by heat, the apparatus purified in a similar manner, 

 and all subsequent access of organisms carefully guarded against. 

 It is only experiments made in this way that can have any 

 weight in deciding the question. 



Leaving now the theory of nitrification, I will proceed to say 

 a few words, firstly, as to the distribution of the nitrifying 

 organism in the soil ; secondly, as to the substances which are 

 susceptible of nitrification ; thirdly, upon certain conditions 

 having great influence on the process. 



The Distribution of the Nitrifying Organism in the Soil. — 

 Three series of experiments have been made on the distribution 

 of the nitrifying organism in the clay soil and subsoil at 

 Rothamsted.. Advantage was taken -of the fact that deep pits 

 had been dug in one of the experimental fields fir the purpose 

 of obtaining samples of the soil and subsoil. Small quantities of 

 soil were taken from freshly-cut surfaces on the sides of these 

 pits at depths varying from 2 inches to 8 feet. The soil re- 

 moved was at once transferred to a sterilised solution of diluted 

 urine, which was afterwards examined from time to time to 

 ascertain if nitrification took place. These experiments are 

 hardly yet completed ; the two earlier series of solutions have, 

 however, been examined for eight and seven months respectively. 

 In both these series the soil taken from 2 inches, 9 inches, and 



