2 Obituary Notices of Fellows deceased. 
papers on the subject, all in his own name, the principal of which were four 
communications to the Chemical Society, bearing the title “On Nitrification,” 
Parts I to IV. 
That the natural conversion of ammonia into nitric acid was the work of 
an organism, had been suggested by A. Miiller as early as 1873, but it had 
been reserved for Schleesing and Miintz to establish definitely that this was 
the case. In 1877 they showed that, when sewage was allowed to percolate 
through a column of sand and limestone, the nitrification which occurred 
during its passage could be prevented by the presence of a sterilising agent 
such as chloroform vapour, and, after such sterilisation, the activity of the 
sand could be resuscitated by inoculating it with a few particles of vegetable 
mould. Questions affecting the problems connected with nitrogen in the soil 
had naturally been amongst those to which the Rothamsted investigators had, 
from the first, devoted themselves, and, consequently, they at once set to work 
to examine such an important observation as that of Schloesing and Mintz. 
A complete verification of it was obtained by Warington, operating with 
garden soil only, and a solution of ammonium chloride, instead of sewage; and 
he was enabled to add the additional information, that nitrification occurred 
only in the dark. This paper appeared within a year of that of Schloesing 
and Mintz. Two and a-half years later he published a second paper which 
added considerably to the facts already established. He showed that the 
nitrifying organism, besides requiring darkness in order to do its work, must 
also be supplied with food for its growth—potash, lime and phosphorus—and 
moreover, that all liberation of free acid must be prevented by the presence 
of some salifiable base, such as ealcium carbonate. He found, also, that after 
the introduction of a small quantity of active soil or solution into a liquid 
capable of nitrification, no action occurred till a certain time had elapsed, this 
period of incubation being probably due to the organisms having to multiply 
to a certain extent before they become sufficiently numerous to produce 
recognisable results. An increase of temperature was found to favour the 
action up to a certain point, and it was shown that various vegetable moulds 
and known bacteria were not the organisms to which nitrification could be 
attributed. Many difficulties, however, still remained to be cleared up, 
notably the want of uniformity of the action, which resulted in the production 
of nitrates in some instances, and nitrites in others. We now know that the 
process is performed by two quite distinct organisms, and that their nutrition 
is, In some respects, wholly different from that of any other organism hitherto 
studied; but until this knowledge was gained, work on the subject was 
singularly difficult, and the results were very perplexing. 
Warington’s third paper on nitrification added considerably to our 
knowledge of the circumstances attending the action, and established the fact 
that the organismsare almost entirely confined to the first nine inches of ordinary 
soil. The distribution of the organism in the soil was dealt with still more 
exhaustively in a subsequent communication in 1887. 
The prize coveted by the workers on this subject was, however, the isolation 
