318 

NATURE 

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 carbonicacid 
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 :— 
Drys@xyeen isd ae No oxidation. 
Dam { In three experiments, only one 
Dae) 6) F 3t) °d... Dlade'slightly, oxidised: 
Dry Carbonic Acid . . . . No oxidation. 
Slight appearance of a white 
j precipitate of the iron, found 
Damp +; . « . + +4 tobe carbonate ofiron. Two 
\ only out of six experiments 
did not give these results. 
Dry carbonic acid and oxygen . No oxidation. 
{Oxidation most rapid, a few 
hours being sufficient. The 
blade assumed a dark green 
colour, which then turned 
brown ochre. 
No oxidation. 
No oxidation. 
Damp oxygen and carbonic acid 
Dry oxygen and ammonia 
Damp ,, PS WAS 
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 presenc2 of carbonic acid in the 
atmosphere, and not its oxygen or its aqueous vapour, 
which determines the oxidation of iron in commonair. 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 :— 
(1) 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 influence 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.—Mr. 
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. Gderi Sm., and of Grindon’s Manchester 
Flora, and the C. fava var. B of Buxton’s Guide. The true 
C. flava (a genuina E.B.), as stated long ago by Mr. Buxton, 
is nowhere met with in the district. Specimens of C. Qderi 
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. 
TAUNTON 
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 archzeological as 
wellas 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. Yarrell, 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 yery nearly allied group in that 
order. Iam 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, aconspicuous mark of the true 
Plover, wouldat oncesuggest this position. The form of thesternum 
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 Jéis for 1865. 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 formerly 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 1798, two more in the next year, and one in 1864. Another 
Devonshire specimen occurred, after a long interval, on the 31st 
December, 1851, near Clovelly, and was recorded by Mr. Gats- 
combe, in the Waturalist. The 31st December seems to have 
been a favourite day with the Great Bustard in North Devon, for 
[ Feb. 16, 1871 
