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Nature
(Thursday, February 16, 1871)

Societies and academies,   pp. 316-320


Page 318


NA TURE
[Feb. I6, x87I
plicated than is stated in our text-books. Therefore the question
may be asked, Is the oxidation of iron due to the direct action of
the oxygen of the atmosphere, or to the decomposition of its
aqueous vapour; or does the very small quantity of carbonic acid
which it contains determine or intensify the oxidation of metallic
iron? To reply to it I have made a long series of experiments,
extending over two years, and which I hope will throw some
light on this very important question. Perfectly cleaned blades
of steel and iron, having a gutta percha mass at one end, were
introduced in tubes which were placed over a mercury trough,
and by a current of pure oxygen conducted to the top of the ex-
perimental tube; the atmosphere was displaced, and it was then
easy to introduce into these tubes traces of moisture, carbonic
acid, and ammonia. After a period of four months, the blades
of iron so exposed gave the following results:-
Dry Oxygen . . . . . . . No oxidation.
Damp ,
Dry Carbo
Damp
Dry carbo:
Damp oxy
Dry oxyge
Damp ,
                       In three experiments, only one
  1. . . . . . .         blade slightly oxidised.
nic Acid   . . . . No oxidation.
                       J Slight appearance of a white
                         lprecipitate of the iron, found
        ,,   . . . . . \ to be carbonate ofiron. Two
                         only out of six experiments
                       \ did not give these results.
nic acid and oxygen . . No oxidation.
                      Oxidation most rapid, a few
                      f hours being sufficient. The
gen and carbonic acid  blade assumed a dark green
                         colour, which then turned
                         brown ochre.
n and ammonia   . . No oxidation.
          ,,  . .   . No oxidation.
The above results prove that under the conditions described,
pure and dry oxygen does not determine the oxidation of iron,
that moist oxygen has only feeble action; dry or moist pure car-
bonic acid has no action, but that moist oxygen containing traces
of carbonic acid acts most rapidly on iron, giving rise to pro-
toxide of iron, then to carbonate of the same oxide, and lastly to
a mixture of saline oxide and hydrate of the sesquioxide of iron.
These facts tend to show that carbonic acid is the agent
which determines the oxidation of iron, and justify me
in assuming that it is the presence of carbonic acid in the
atmosphere, and not its oxygen or its aqueous vapour,
which determines the oxidation of iron in common air. Although
this statement may be objected to at first sight, on the ground
of the small amount of carbonic acid gas existing in the atmo-
sphere, still we must bear in mind that a piece of iron, when
exposed to atmospheric influences, comes in contact with large
quantities of carbonic acid during twenty-four hours. These re-
sults appeared to me so interesting that I decided to institute
several series of experiments.  When perfectly clean blades of
the best quality of commercial iron are placed in ordinary Man-
chester water, they rust with great facility, but if the water is
previously well boiled and deprived of oxygen and carbonic acid,
they will not rust for several weeks. Again, if a blade of the
same metal is half immersed in a bottle containing equal volumes
of pure distilled water and oxygen, that portion dipping in
the water becomes rapidly covered with the hydrate of the
peroxide of iron, whilst the upper part of the blade remains
for weeks unoxidised; but if a blade be placed in a mixture of
carbonic acid and oxygen, a very different chemical action
ensues, as not only that portion of the blade dipping in the
water is rapidly attacked, but the upper part of it immediately
shows the result of chemical action, and also the subsequent
chemical reactions are greatly modified by the presence of the
carbonic acid. For in this case that portion of the blade is
only covered with a film of carbon, together with a dark deposit
composed of carbonate of the protoxide and hydrate of the
sesquioxide. The fluid, instead of remaining clear, becomes
turbid. These series of experiments substantiate the interesting
fact observed-that carbonic acid promotes oxidation. A long
series of experiments were also made to try and throw some
light on the curious fact, first published by Berzelius, subse-
quently studied by other chemists, and well known to soap and
alkali manufacturers, namely, that caustic alkalies prevent the
oxidation of iron; my researches can be resumed as follows:-
(I) that the carbonates and bicarbonates of the alkalies possess
the same property as their hydrates; and (2) that if an iron
blade is half immersed in a solution of the above-mentioned
carbonates, they exert such a preservative infuence on that por.
tion of the bar which is exposed to an atmosphere of common
air (oxygen and carbonic acid), that it does not oxidise even after
a period of two years. Similar results were obtained with sea
water, to which had been added carbonates of potash and soda.
  Microscopical and Natural History Section, January 9.-Nr.
J. Baxendell, President of the Section, in the chair.   "On
Carex flava L., and its allies, of the Manchester Flora," by
Charles Bailey. The prevailing form in the district, and one very
common to the south of Manchester, is the Carex lepidocarpa
Tausch. ; this is the C. (EderiSm., and of Grindon's Manchester
Flora, and the C. flava var. X of Buxton's Guide. The true
C. ]laza (a genuina E. B.), as stated long ago by Mr. Buxton,
is nowhere met with in the district.   Specimens of C. (Ederi
Ehrh. from Mere Mere, the locality mentioned in Buxton's Bo.
tanical Guide, were recently exhibited at a meeting of the Society,
and the sandhills at Southport are, so far as I know, the only
locality in the neighbourhood for this species.
                           T AUNTON
  Somersetshire Natural History Society, February 6.-
The following notice was read by Mr. Cecil Smith.-The Great
Bustard has now so long been considered extinct in England,
that we may look upon it as interesting in an archaeological as
well as in a natural history point of view. This bird, one of a
flock of eight that made their appearance on the last day of the
old year at Braunton, near Barnstaple, in North Devon, is pro-
bably a young hen bird of the first, certainly not more than the
second, year. On looking at this bird, perhaps, one of the first
things that strikes one is the shape of the foot, the three toes in
front and no hind toe; and this brings me at once to the subject of
classification or order. Varrell, whose system is best known and
most generally adopted, has made the bustards a group of the
Rasoreal order, where I cannot help thinking they are not a little
out of place, there being no very nearly allied group in that
order. I am much more inclined to agree with Baron Cuvier
and some of the other older systematic authors who placed the
bustards amongst the Grallatores or Stilted birds, where they
seem naturally to fall into place next to their near relations, the
Plovers; the absence of the hind toe, a conspicuous mark of the true
Plover, wouldatoncesuggest thisposition. Theformofthesternum
or breast bone also points to a relationship with the plovers rather
than with any of the Rasores.  Another point which can scarcely
be passed over in silence in a paper on the Great Bustard is the
gulor pouch. It seems surprising that the use, and even the
existence, of this pouch has so long been a matter of doubt and
perplexity to naturalists. Much light has, however, lately been
thrown on the subject by Prof. Newton, Mr. Bartlett, and Dr.
Murie, and it seems finally to have been set at rest by Dr.
Cullen, the result of whose examinations has been reported in
the Ibis for  i865.   He readily found the opening into the
pouch under the tongue, and describes it as large enough to
admit the little finger; the pouch itself, he says, extended as far
down as the furcular bone, and was a separate and distinct,
though delicate, bladder.  He then describes the performances
of the male bustard in the breeding season, at which time, he
says, it makes a peculiar sound, resembling the word "ook,"
and he strongly favours the idea that the pouch is merely an
organ of sound, and that it is acted upon by the muscular tissue
covering it ; in fact, that it is a sort of bird bag-pipe, and seems
not to produce much more melodious sounds. Although the Great
Bustard was fonnerly resident in England throughout the year, it is
generally a migratory bird, its migratory propensities being much
developed by stress of weather and scarcity of food; whether either
of these causes or the war in France, has been the reason for the
present unusual migration to England is perhaps difficult to say;
myself, I should be inclined to think bad weather and the con-
sequent loss of food the more probable cause. The gradual ex-
tinction of the Great Bustard in England has been the general
theme of most of onr writers on ornithological subjects from the
time of Bewick and Montagu to the present time of Mr. Steven
son, who in his still unfinished work on the " Birds of Norfolk,"
gives a most interesting account of the decline and fall of the
Great Bustard in that county. In Devonshire, where this bird
was killed, the Great Bustard, although never resident, seems
from time to time to have paid occasional migratory visits.
Montagu mentions the occurrence of one near Plymouth in the
year I 798, two more in the next year, and one in 1864. Another
Devonshire specimen occurred, after a long interval, on the31st
December, i85I, near Clovelly, and was recorded by Mr. Gats-
combe, in the Naturalist. The 31st December seems to have
been a favourite day with the Great Bustard in North Devon, for
3i8


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