408 
NATURE : 
[March 1, 1883, 
nuisance arising from smoke from factory and other 
furnaces, but in the present movement it is evident that 
the importance of the domestic fireplace as a foe, if not 
the chief one, to the purity of the air of cities, has been 
generally recognised and has been the main object of 
attack. 
It is not a little remarkable that, although elaborate 
experiments have been made from time to time with a 
view to ascertain the nature and composition of the gases 
generated in furnaces, but little attention has been 
devoted to the gases given off from stoves and grates. 
On the Committee of the recent Smoke Abatement Exhi- 
bition chemists were well represented, and this brief notice 
will mainly refer to the genera] chemical results that have 
been obtained. 
The examination of the gases withdrawn from flues to 
which stoves and grates were attached, was intrusted 
to Prof. Chandler Roberts, who at first considered that the 
analysis of representative samples might best be made by 
the aid of the rapid methods of gas analysis arranged by 
Orsat. In view, however, of the peculiar conditions under 
which the tests had to be made, and bearing in mind that 
more than one hundred appliances were submitted for 
testing in the limited time during which the Exhibition 
was open, Prof. Roberts submitted a plan to the Com- 
mittee which received its approval. 
He points out in his report that the first researches on 
chimney gases are due to Péclet, who published some 
results of analysis in 1828, but Péclet’s results and those 
of different experimenters who followed him were open 
to the objection that the samples submitted to analysis 
were only small fractions of the total gases in the flues, 
and as the samples were not taken with sufficient fre- 
quency they could not represent the mean composition of 
the gaseous mixture passing up the chimney. This grave 
defect was, however, remedied by Scheurer-Kestner in an 
elaborate research on the composition of the flue-gases 
of boiler furnaces, which will always be the basis of future 
experiments in this direction, and to which frequent 
allusion is made in the Report. The details of the method 
adopted are given in the Report itself ; it will be sufficient 
to say here that the gases were withdrawn through a fine 
slit in a tube extending across the flue, an_arrange- 
ment which rendered it possible to draw the gases uni- 
formly from the entire diameter of the ascending current 
of gas in the flues. The effluent gases were withdrawn 
by aspiration through a tube loosely filled with asbestos 
to retain the solid particles of carbon and soot; they 
then passed through a U-tube filled with chloride of 
calcium to absorb water, and thence through three U- 
tubes filled with soda-lime to absorb carbonic anhydride ; 
the gases were then led to a tube of porcelain filled with 
cupric oxide and heated to redness by means of a small 
furnace. The complete combustion of the remaining gases 
was thus effected, the carbonic oxide being burnt to car- 
bonic anhydride, and the hydrocarbons and free hydrogen 
to aqueous vapour and carbonic anhydride ; the water was 
retained in a U-tube filled with chloride of calcium, and 
the carbonic anhydride in two other soda-lime tubes; 
the residual gases (unconsumed oxygen and nitrogen) 
then passed to the aspirator, a chloride of calcium tube 
being interposed to prevent any moisture from the aspirator 
from penetrating the system of tubes. 
It will be evident that this plan renders it possible to 
compare the relative proportion of the completely burnt 
products of combustion with those in which combustion has 
been imperfect. With regard to the proportion of carbon 
lost as soot, the evidence afforded by the results of the 
tests made at the Exhibition, although they do not un- 
fortunately render it possible to give a clear and precise 
answer to the question, are sufficiently definite to show 
that the amount probably does not exceed I per cent. of 
the total carbon in the fuel, and is in many cases far less. 
The coal] used in testing the grates and stoves was 
either ‘ Wallsend,’ which yielded 67°i per cent. of coke, 
or Anthracite, giving 94 per cent. on distillation in a_ 
closed vessel. 
With regard to the completeness of the combustion, the” 
carbon present in the form of carbonic anhydride varied 
in relation to that present as carbonic oxide and as 
hydrocarbons, C.Hy, within the limits of 1,000 to 4 and © 
1,000 to 375, but of the whole eighty-six tests in only three 
was the number indicating imperfect combustion below © 
Io, and in only nine cases was it above 200, and six of 
these nine cases (three grates and three stoves) were 
worked purposely for ‘‘ slow combustion.” 
The total amount of carbon present in the gases 
ascending the flue (either in the free state or combined — 
with carbon) bore a relation to the hydrogen present 
which varied between the limits of 1,000 to 8 and 1,000 © 
to 259, the latter probably being due to the fact that the © 
grates and stoves were tested whilst the mortar in which 
they were set was still wet. 
The mean of the results of the tests of the seventeen 
best grates shows that the loss of carbon in the form of 
carbonic anhydride and hydrocarbons is about 3°4 per 
cent. of the carbon in the fuel used (in the case both of 
Anthracite and Wallsend), the mean for the whole of the 
grates being about g per cent. of the total carbon. 
The comparative imperfection of the combustion 
shown in some of the tests is hardly to be wondered 
at when it is remembered that the bituminous coal em- 
ployed yielded on distillation no less than 32 per cent. 
of volatile matter, and that in the case of many of the 
appliances the cold fuel was simply charged on to the 
top of a mass of coal already in the state of incandescence. 
Professor Roberts cautiously points out that all that 
has hitherto been done in this series of tests “merely 
renders it possible to select certain typical appliances 
which deserve more detailed examination.’’ He appears, 
however, to have spared no pains to render this very | 
laborious investigation as complete as the circumstances 
allowed, and the Chemical section of this Report is cer- 
tainly one of the most important contributions ever made 
to our knowledge of the combustion of fuel. 
E. FRANKLAND 
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} 
NORTH AFRICAN ETHNOLOGY 
Sahara und Sudan: Ergebnisse Sechsjahriger Retsen in 
Afrika. Von Dr. Gustav Nachtigal. Part II. (Berlin: 
1881.) 
EARLY a decade has elapsed since Dr. Nachtigal’s 
return to Europe after his travels in East Sahara 
and Central Sudan during the years 1869-74. Most of — 
the geographical and ethnological results of his researches 
