352 Ward . — Recent Publications bearing on the 
The results of experiments with saw-dust, humus, roots, &c. 
led to the inference that free nitrogen is fixed, and that if oxy- 
gen is absent the hydrogen disengaged — being unable to form 
water — unites with the nitrogen to form some compound. 
This led to experiments under other conditions, and nitro- 
gen was passed over warmed mixtures of glucose and soda, 
and the results confirmed the authors’ expectations, but are 
chiefly of interest as leading to other suggestions. 
Experiments based on these led to the conclusion that if 
nitrogen is passed, in the cold, over saw-dust or glucose, 
alone or mixed with alkalis, some of the nitrogen is retained, 
‘ fixed ’ in combination. It is thus demonstrated that, ist, ‘ the 
nitrogen of the atmosphere may be fixed by vegetable sub- 
stances, even in the cold and under conditions analogous to 
those which are met with in cultivated soils ; 2nd, this fixation 
is singularly promoted by the absence of oxygen.’ 
Thus when organic matter decomposes in an atmosphere 
deprived of oxygen, or nearly so, giving rise to carbonic acid 
and to hydrogen, the nitrogen of the atmosphere is absorbed 
and unites with the hydrogen to form ammonia. 
It appears that Thenard and others have shown that in the 
soil there are, as it were, two atmospheres — one, an oxydising 
atmosphere in the upper layers, the other, a reducing atmo- 
sphere lower down. Deherain points out that ‘the energy 
of slow combustion is much greater than is usually supposed : 
germinating seeds in a closed space absorb the oxygen, even 
to the last trace, in a few days ; aquatic plants kept in 
water in the dark take from it all the oxygen it contained. 
If the composition of the air confined in a heap of manure is 
determined, there is found only nitrogen and carbonic acid 
mixed with a slight proportion of combustible gas, oxygen 
is absolutely wanting. This is an experiment which we have 
repeated at Grignon for several years without variation.’ 
Thus there is in the soil, at a certain depth, an atmosphere 
devoid of oxygen — the decomposition of organic substances 
may give rise to hydrogen — the latter may meet with nitrogen 
and form ammonia. 
