ON THE COMBUSTION OF GAS FOIl ECONOMIC PUIIPOSES. 
303 
of decomposing carbonic acid whenever brought into sunshine. But for this they must 
be kept in an atmosphere containing a supply of oxygen ; without this they soon die, 
as Boussingault thinks, from asphyxia. The oxygen in darkness is slowly transformed 
into carbonic acid, through an operation which is presumed to go on continually, 
whether in light or darkness, and to answer to respiration. Of course a healthy and 
active leaf decomposes far more carbonic acid in the light than it forms in darkness. In 
eighteen experiments, with Oleander-leaves exposed to the sun from eight a.m. to 
five P.M., in an atmosphere rich in carbonic acid, a square metre of foliage decomposed 
on the average over a litre of carbonic acid per hour, while in darkness only of a 
litre of carbonic acid was produced per hour. In air which contains oxygen and car¬ 
bonic acid, leaves will go on indefinitely producing oxygen in the presence of carbonic 
acid, and carbonic acid in the presence of oxygen. But the latter, though relatively 
small in amount, seems to be necessary to the preservation. of their vitality. In hydro¬ 
gen, carburetted hydrogen or nitrogen, as well as in pure carbonic acid, they soon lose 
their decomposing power, and die from the impossibility of respiration, i.e. are 
asphyxiated. 
Leaves confined in a limited portion of atmospheric or other air over mercurjq lose the 
power of decomposing carbonic acid ; and the experiments pretty clearly show that they 
lose it through the deleterious action of the vapour of mercury. It is thought remark¬ 
able that the leaf does not under these circumstances at all lose the power of transform¬ 
ing oxygen into carbonic acid; but that is what we should expect, for the carbonic acid 
so evolved (whether its evolution be called respiration or not) must be a product of de¬ 
composition of the leaf’s contents or substance. 
VVe owe to Boussingault and his assistant Lewy the idea of determining the com¬ 
position of the air contained in a fertile soil, and the fact that this air in a strongly- 
manured soil contains a very large percentage of carbonic acid. Boussingault has now 
devised an experiment by which the air contained in a branch of an Oleander in full 
vegetation was extracted. It proved to be nitrogen 88'01 per cent., oxygen G‘G4, car¬ 
bonic acid 5'35 per cent.,—being about the composition of the air from a well-manured 
soil. This carbonic acid carried into the leaves with the sap, and also that which they 
may absorb directly from the atmosphere, decomposed along with water under sunlight, 
must be the source of the glucose (Cj.jIIj.^Oio) which it is the principal function of 
foliage to produce. This glucose, in fixing or abandoning the elements of water, be¬ 
comes sugar, starch, cellulose, or other hydrates of carbon, which, in whatever part of 
the plant accumulated or deposited, and however transformed or re-transformed, must 
always have originated from carbonic acid and water in the green parts of plants. In 
closing his present paper with some illustrations of this now familiar view, Boussingault 
announces that his more recent experiments will enable him to demonstrate the direct 
formation of saccharine matter by the green parts of vegetables exposed to the light.— 
Amer. Journ. Sci. and Arts. 
ON THE COMBUSTION OF GAS FOE ECONOMIC PURPOSES. 
BY HENRY LETHEBY, ESQ., M.B., 
[A Lecture delivered before the British Association of Gas Alanagers, at St. Martin’s 
Hall, London, on Wednesday, May 23, 18GG.] 
{Continuedfrom p. 170.) 
Lastly, there are cases where the amount of carbon in the vaporous matter is so abun¬ 
dant that contrivances are needed for its oxidation. All these contrivances are 
plans for diminishing the supply of the combustible and increasing the flow of air. 
In the paraffin candle the wick is adapted for a small supply of the material; and 
in the benzole and paraffin lamps there are caps and deflectors, with slights for blowing 
the air upon the sides of the flame. In the camphine lamp there are additional deflec¬ 
tors in the form of a central button, and a throttled chimney, for directing the air upon 
the inside and outside of the flame; and in the Carcel lamp the oxidation is increased by 
the length of the chimney. In all cases, however, the points for consideration are—the 
