96 
SIR J. B. LAWES AND PROFESSOR J. H. GILBERT ON THE 
there was a loss of nitrogen; whilst in one with three lupins, and in one with one 
lupin there was a gain. Frank considered it probable that where a loss was 
indicated with vegetation, there had nevertheless been a gain, but not enough to 
compensate the loss. 
In another experiment, with a soil about 12 times as rich in nitrogen, and many 
times richer than ordinary arable soils, he found a loss, due mainly to evolution of 
free nitrogen ; and referring to this result, he says that if such losses take place 
in ordinary agriculture there must be natural compensation. 
In the experiments in the deep and narrow vessels, without drainage, and without 
plants to cause evaporation, movement, and aeration, loss by evolution of free 
nitrogen is only what would be expected. Such loss would also be expected in the 
two cases of loss with growth, in both of which there was admittedly decomposing 
organic matter. It was also to be expected in the very rich soil. But it is doubtful 
whether, in the two cases of gain with growth, and therefore movement within the 
soil, and aeration of it, there would be any loss. In none of the experiments with 
loss, however, were the conditions comparable with those of ordinary soils, under 
ordinary treatment, and the losses found cannot be taken as any indication of what 
takes place in ordinary practice. It is probable that in such practice the loss by 
evolution of free nitrogen is much less than is generally assumed in discussions of 
this subject. Doubtless there is, however, frequently considerable loss by the 
drainage of nitrates. 
Frank considers that, independently of direct evidence against the supposition that 
the gains were due to the absorption of combined nitrogen from the atmosphere, an 
objection to such a view is that it would not explain the circulation of nitrogen 
in nature; and his main conclusion is, that there are two actions going on within the 
soil, one liberating nitrogen, and the other bringing it into combination, the latter 
favoured by vegetation. 
Upon the whole it would seem that the losses found by Frank may be explained 
by the special conditions of the experiments themselves ; whilst the gains, if not to 
be accounted for by sources of error incidental to experiments made in free air, can 
only be explained by fixation in some way. 
The most remarkable of the residts indicating the fixation of free nitrogen 
are those of Professor Hellriegel and Dr. Wilfarth. Hellriegel found that 
whilst plants of the gramineous, chenopodiaceous, polygonous, and cruciferous families 
required combined nitrogen to be supplied within the soil, papilionaceous plants did 
not depend on such soil-supplies. 
Peas sometimes grew luxuriantly in washed sand with nutritive solutions free from 
nitrogen, but sometimes failed, root-nodules being developed coincidently with 
luxuriance, but not without it. But when to the non-nitrogenous sandy matrix a 
few c.c. of the watery extract of a rich soil were added, the luxuriance was always 
marked, as also was the development of the root-nodules. Lupins, however, failed 
when treated in the same way, but succeeded when seeded by a watery extract of a 
