101 
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 imme- 
diately shows the result of chemical action, and also the sub- 
sequent chemical re-actions 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, subsequently 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: — 
1st. That the carbonates and bicarbonates of the alkalies 
possess the same property as their hydrates ; and 
2nd. That if an iron blade is half immersed in a solution 
of the above-mentioned carbonates, they exert such a pre- 
servative influence on that portion of the bar which is 
exposed to an atmosphere of common air (oxygen and 
carbonic acid), that it does not oxidize 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 9th, 1871. 
J. Baxendell, F.B.A.S., President of the Section, 
in the Chair. 
“ On Carex jtava L., and its allies, of the Manchester 
Flora,” by Charles Bailey. 
