542 
NATORLE 
[OcTOBER 5, 1899 
field, contained a similar quantity of nitrate to that found 
in the exhausted soil around the plant at the end of the 
season. ‘The next year he finds that the soil of the field, 
when deprived of vegetation, doubled its contents in 
nitrates between June 4 and “the end of the season” ; 
but this rate of increase was insufficient to account for the 
nitrates found in the crop the previous year / Finally, to 
prove that the plant contains a nitrifying agent, a single 
experiment is made by introducing a fragment of the 
stem of Amaranthus into a flask containing 300 grams of 
sterilised and exhausted soil. At the end of eleven weeks 
six milligrams of saltpetre were found in the soil. A 
blank experiment, made with soil only, was for some 
reason only continued for six weeks. 
Data such as these are quite insufficient to convince a 
critical reader. Our confidence in the investigation is 
not increased by reading that the growth of a single 
crop in the field diminished the nitrogen in the soil from 
275 to 173 per cent., and the potash of the soil in the 
neighbourhood of the roots from *64 to °47 per cent. 
Nor by remarking that the same figures for nitrates in 
the soil are first quoted as kilograms, and are afterwards 
always spoken of as grams. 
The whole of the first volume is occupied with an 
account of investigations on the fixation of atmospheric 
nitrogen by soil and plants. M. Berthelot has been a 
pioneer in this branch of inquiry. The peculiar function 
of the organism forming the nodules on the roots of 
leguminous plants is now universally recognised. A 
similar case of symbiosis between a nitrogen-assimilating 
organism and certain algz is also well known. Not so 
well known is the isolation of a bacillus from the soil by 
Winogradsky, which when supplied with sugar, and 
protected from the action of oxygen, is capable of 
assimilating atmospheric nitrogen. This organism suc- 
ceeds in assimilating nitrogen from ordinary air when 
it is associated with azrobic organisms which appropriate 
the oxygen, and thus produce conditions suitable for the 
growth of the bacillus assimilating nitrogen. 
Both in the case of the reaction in the leguminous 
rootlets and algze, and in the case of the reaction 77 
vitro, studied by Winogradsky, we have a clear in- 
dication of the source of the chemical energy which ac- 
complishes the difficult task of bringing nitrogen into a 
state of organic combination ; in every case we have 
carbohydrates abundantly present, and in Winogradsky’s 
experiments we have a demonstration that the quantity 
of sugar fermented is a measure of the quantity of 
gaseous nitrogen assimilated. 
With this principle before us we should suppose that a 
soil entirely destitute of vegetation could fix nitrogen 
only at the expense of its own organic matter; carbon 
would, in fact, be lost in the operation of fixing nitrogen. 
If, on the other hand, certain green algze or leguminous 
plants were present, fixation of nitrogen might be accom- 
panied by an actual gain of organic matter. 
According to Berthelot’s experiments, soils destitute of 
visible vegetation may gain large quantities of nitrogen 
when exposed to air. Even subsoils of argillaceous sand 
or clay, containing mere traces of carbon or nitrogen, 
are capable of gaining considerably in nitrogen when ex- 
posed to air. From an agricultural point of view, the 
quantities of nitrogen fixed are very considerable. Layers, 
NO. 1562, VOL. 60] 
7 inches deep, of three surface soils from Meudon, fixed 
in 11 weeks from 70 lbs. to 130 lbs. of nitrogen per acre, 
quantities equivalent to 6-11 tons of farmyard manure. 
If this enrichment of soil by mere exposure to air is a 
fact, we shall be very anxious to know what are the pre- 
cise conditions and limitations of such a beneficial action. 
Scientific agriculturists will be loath to admit that the 
exposure of a soil uncovered by vegetation tends to its 
permanent enrichment ; the process of weathering tends, 
on the contrary, to the exhaustion of soil capital, and not 
to an increase of nitrogenous organic matter. 
Berthelot’s trials of various organisms yielded results 
of a similar favourable character. Out of seven organisms 
tried five produced an active fixation of nitrogen. The 
composition of the medium was apparently indifferent, 
for a mixture of certain bacilli from soil with kaolin de- 
termined an increase of 32 per cent. of the original 
nitrogen in one case, and an increase of 150 per cent. 
in another. Among the organisms fixing nitrogen, 
Berthelot includes the common mould Aspergillus niger. 
In the last section of this volume Berthelot describes 
experiments which lead him to the conclusion that the 
natural electrical conditions, both of soil and plant, aid in 
bringing about the fixation of nitrogen from the air. 
It is to be regretted that the large amount of work 
contained in these volumes is not of a more thorough 
and definite character, but we are very thankful that the 
investigations have been published. R. W. 
OUR BOOK SHELF. 
Bird Life in an Arctic Spring; the Diaries of Dan 
Meinertzhagen and R. P. Hornby. Edited by Mrs. G. 
Meinertzhagen. Pp. ili +150. Illustrated. (London: 
Porter, 1899.) 
A PATHETIC interest attaches to this volume, as being 
practically a memorial to a most promising and talented 
young ornithologist, whose life was unhappily cut short 
almost at the outset of his career. The late Mr. D. 
Meinertzhagen was essentially a lover of bird-life, and 
thus a naturalist in the very best sense of that somewhat 
abused word. But he was much more than this, being 
an artist of great talent, whose sketches and etchings of 
birds form some of the most beautiful delineations of 
feathered life it has been our fortune to see. In addition 
to those illustrating the text itself, nearly thirty of these 
talented sketches have been photographically reproduced 
as an appendix to the present volume, and serve not only 
to enhance the general interest of the latter, but likewise 
to convey an excellent idea of the artistic capacity of the 
autho of the journal which constitutes its main claim to 
attention. 
As we gather from the preface, the book is mainly 
intended for private circulation, and only a limited 
number of copies are offered to the general public. On 
the whole, the editor has exercised a wise discretion in 
endeavouring to preserve the journal of her son as much 
as possible in its original form, although it must be con- 
fessed that a little fuller supervision on the part of a 
trained ornithologist than has been permitted would have 
been advantageous in a few instances. 
The journal is divided into two portions, the first and 
longer by Mr. Meinertzhagen, and the second by his 
companion Mr. Hornby. The trip to Lapland, of which 
these form the chronicle, was undertaken in 1897 ; and 
the journal of the originator breathes out the enthusiasm 
of an ardent bird-lover. The two companions appear 
toihave visited spots to which few if any Englishmen 
