1892.] on 3Iicro-organisms in their Relation to Chemical Change. 525 



More recent researches of Winogradsky have shown that the first 

 of these two alternative hypotheses is the correct one, for by making 

 cultivations of soil in a solution containing nitrous acid and no 

 ammonia, Winogradsky has succeeded in isolating a micro-organism 

 which possesses the po'A^er of converting nitrous acid into nitric acid, 

 but has no power of attacking ammonia. [Lantern-slide of Nitric 

 Ferment (Winogradsky.)] 



This second organism or nitric ferment, as we may call it, 

 resembles in its activity the purely chemical oxidising agent — 

 potassium permanganate — which, as we have seen, has no action on 

 ammonia, but readily converts nitrous into nitric acid. 



The process of nitrification in the soil now becomes intelligible in 

 its entirety. It is the work of two independent organisms, the first 

 of which converts ammonia into nitrous acid, whilst the second 

 transforms into nitric acid the nitrous acid produced by the first. 



There is a point in connection with the distribution of nitric acid 

 in nature which is exceedingly remarkable, and which forces itself 

 upon the attention of every student of the process of nitrification. 

 Although nitric acid is generally so scantily present in the soil, there 

 is one notable exception to this rule, for in the rainless districts of 

 Chili and Peru there are found immense deposits of nitrate of soda, 

 or Chili saltpetre, as it is called, which would appear to represent the 

 result of a gigantic nitrification process in some previous period of 

 the earth's history. The vast quantities of this material which occur 

 in these regions of South America can be gathered from the fact that 

 its exportation has for years being going on at the rate indicated by the 

 following figures : — During the first six months of 1890 there were 

 brought to the United Kingdom 90,000 tons, and to the European 

 Continent 480,000 tons. 



From the presence of such altogether enormous quantities, one is 

 almost tempted to hazard the suggestion that in this particular region 

 of the earth, under some special circumstances of which we know 

 nothing, the nitrifying organisms must have been endowed then and 

 there with very much greater powers than they possess to-day, and 

 it is particularly noteworthy that in a recent examination of soils 

 from nearly all parts of the earth, one coming from Quito, and there- 

 fore not far distant from these nitrate fields, was found to possess the 

 power of nitrification in a degree far beyond that exhibited by any other 

 soil hitherto experimented with. Is it not possible, perhaps, that we 

 have in these vigorous nitrifying organisms of the soil of Quito, the 

 not altogether unworthy descendants of that Cyclopean race of nitri- 

 fying bacteria, which must have built up the nitrate wealth of Chili 

 and Peru, and thus countless ages ago founded the fortunes of our 

 nitrate kings of to-day ? 



But these nitrifying organisms have also assisted in teaching us 

 a highly important lesson in connection with the maintenance of life. 



The facts which I have already referred to concerning the multi- 

 plication of micro-organisms in distilled water, and the continuation 



