of an occurrence
of the disasters that accompanied the old process.

Another example will show us the microbes in activity in the earth. Let
us take a pinch of vegetable mould, water it with ammonia compounds, and
analyze it, and we shall find nitrates therein. Whence came these
nitrates? They came from the oxidation of the ammonia compounds brought
about by moistening, since the nitrogen of the air does not seem to
combine under normal conditions with the surrounding oxygen. This
oxidation of ammonia compounds is brought about, as has been shown by
Messrs. Schloesing and Muntz, by a special ferment, the _Micrococcus
nitrificans_, that belongs to the group of Bacteriacae. In fact, the
vapors of chloroform, which anesthetize plants, also prevent
nitrification, since they anaesthetize the nitric ferment. So, too, when
we heat vegetable humus to 100 deg., nitrification is arrested, because the
ferment is killed. Finally, we may sow the nitric ferment in calcined
earth and cause nitrification to occur therein as surely as we can bring
about a fermentation in wine by sowing _Mycoderma aceti_ in it.

The nitric ferment exists in all soils and in all latitudes, and
converts the ammoniacal matters carried along by the rain into nitrates
of a form most assimilable by plants. It therefore constitutes one of
the important elements for fertilizing the earth.

Finally, we must refer to the numerous bacteria that occasion
putrefaction in vegetable or animal organisms. These microbes, which
float in the air, fall upon dead animals or plants, develop thereon, and
convert into mineral matters the immediate principles of which the
tissues are composed, and thus continually restore to the air and soil
the elements necessary for the formation of new organic substances.
Thus, _Bacillus amylobacter_ (Fig. 2, II.), as Mr. Van Tieghem has
shown, subsists upon the hydrocarbons contained in plants, and
disorganizes vegetable tissues in disengaging hydrogen, carbonic acid,
and vegetable acids. _Bacterium roseopersicina_ forms, in pools, rosy or
red pellicles that cover vegetable debris and disengage gases of an
offensive odor. This bacterium develops in so great quantity upon low
shores covered with fragments of algae as to sometimes spread over an
extent of several kilometers. These microbes, like many others,
continuously mineralize organic substances, and thus exhibit themselves
as the indispensable agents of the movement of the matter that