56 
NATURE 
| May 21, 1885 
danger.” “It may, however, play an important part in 
aggravating the consequences of a firedamp explosion.” 
I had myself keenly felt how difficult it would be after a 
verdict of this kind, emanating from such high authorities, 
to make further progress in the work of convincing 
practical mining men of the truth of the views I, had 
previously advocated in the pages of the Royal Society’s 
Proceedings. Yor that reason, and in the absence of some 
powerful weapon wherewith to meet the French Com- 
missioners with some chance of success, I have hitherto 
desisted from doing battle with them, although I have 
been satisfied they were in error from the first. The 
required weapon has been provided by Herr Hilt, the 
spokesman of the Prussian Commission, and may now, 
I think, be made use of without much fear of future 
contradiction. 
Speaking of coal-dust from Pluto Mine, in Westphalia, 
Herr Hilt says, as the outcome of a long series of 
practical experiments on the largest scale yet attempted : 
“Es kann keinem Zweifel unterliegen dass mann mit 
dieser Staubsorte bei Verlangerung der Strecke und 
Streuung auch der Flamme eine beliebige Lange wurde- 
gebenkénnen. Ganz ahnlich erhalt sich der Staub von 
Neu Iserlohn.” Or: “There can be no doubt that with 
this kind of dust the flame could be lengthened out to 
any desired extent, provided the gallery and the layer of 
dust on its floor were made equally long.” “ The dust of 
‘Neu Iserlohn behaves in exactly the same way.” ? 
After carefully examining the details of this report, I 
think it not improbable that many, if not most, of the 
other twenty-four kinds of coal-dust that were subjected 
to experiment would have given results similar to those 
which led to the foregoing remarks had they been em- 
ployed in the same state of minute subdivision. Ditfer- 
ences in chemical composition do not appear to haye as 
much effect in controlling the length of flame produced 
by a given dust under a certain set of conditions as the 
comparative fineness of the particles of which it is com- 
posed. In order to show the effect of fineness Herr 
Margraf has divided the dusts into five classes, as 
follows :— 
Length of Flame pro- 
duced by firing 230 
grm. of powder in 
cannon next floor, the 
floor being strewn 
with coal-dust for a 
length of ro m. 
21 to 31m. 
Designation 
Number of Dusts in each Class. _of 
Class. 
Five, beginning with Pluto Very fine 
Twelve, ending with Camp- | Fine Hie ST Se 
3 to 21m. 
hausen ... .. 
Four Medium 12 to 15 m. 
Five Coarse .. 6to 12m. 
Some experiments were also made with dust passed 
through sieves having meshes of various widths, which 
showed that the finer the state of subdivision, the longer 
was the corresponding flame. 
From this it is obvious that before anything definite 
can be ascertained regarding the influence of chemical 
composition, it will be necessary to reduce the dusts to a 
uniform standard of fineness. Herr Margraf proposes to 
do this by passing them through a sieve with meshes I mm. 
wide. I am afraid, however, that some more exact method 
of effecting a separation of the very fine from the moder- 
ately fine particles will have to be resorted to before a 
satisfactory result can be looked for. A current of air 
ascending slowly at a uniform rate would be a better 
means than any conceivable kind of sieve. 
I have on several previous occasions pointed out that 
when a colliery explosion has been begun in a dry mine 
the coarser particles of coal-dust are winnowed from the 
finer ones by the blast of air which sweeps through the 
workings in advance of the flame. It seems to me that 
‘It may be instructive to compare this conclusion with the second 
sentence of No. r paper, ‘‘On the Influence of Coal-dust in Colliery Explo- 
sions,” Proc. Roy. Soc., 1876; the second last sentence of No. 2 paper, 7dzd., 
1879; the conclusion of No. 3 paper, zéid., 1881.—{Abstract). 
under these circumstances experiments made with any 
other than the finest particles of each kind of dust can 
serve no practicable purpose whatever, and that any 
general conclusions drawn from them must necessarily be 
misleading. It is further highly probable that this is the 
rock upon which the French Commission was ship- 
wrecked. 
They had ascertained by actual experiment that, as the 
coarser particles of any given dust were removed by sift- 
ing, the flame produced under the same set of conditions 
became longer and larger in proportion to the fineness of 
the remaining dust. Yet they failed to carry the argu- 
ment to its legitimate conclusion. They appear to have 
been misled either by too much speculation, or by the 
negative results of their experiments, due, it may be, to 
the smallness of the scale upon which they were made. 
They finally pronounced coal-dust to be an element of 
very secondary importance in colliery explosions, thereby 
allowing a splendid opportunity to slip from their grasp. 
The Prussian Commissioners were not slow to take 
advantage of the opening thus afforded them. Thanks 
partly to the large scale upon which they have set to work, 
| partly to the natural fineness of Pluto and New Iserlohn 
dust, they have been fortunate in obtaining a series of 
positive results which amply confirm those previously 
obtained with the somewhat smaller apparatus belonging 
to the Lords of Committee of Council on Education set 
up in this country under the auspices of the Royal Society 
(No. IV. paper, “ On the Influence of Coal-dust in Colliery 
Explosions,” Proc. Roy. Soc., 1881). 
The dust brought from Camphausen Colliery does not 
appear to stand very high on Herr Margraf’s list, and 
yet, since the publication of the memoir, that colliery has 
been devastated by one of the most violent explosions on 
record, in which it is admitted, I believe, that coal-dust, 
and not fire-damp, was the principal agent of destruction. 
Are we to conclude from this that the nine dusts which lie 
between Pluto and Camphausen in the order of relative 
danger are equally liable to produce a flame of indefinite 
length under like favourable conditions? and, if so, is 
| it not obvious that the experiments are not as reliable 
as might be wished, since they fail to tell us so ? 
Before concluding, I might mention that Herr Hilt 
refers to and agrees with a remark made by MM. Mallard 
and Le Chatelier to the effect that the method of experi- 
ment followed by Sir Frederick Abel and myself when 
using the apparatus described in my first paper was “too 
little exact ” to determine accurately what percentage of 
gas is required to render a mixture of coal-dust and air 
inflammable. My earliest experiments here referred to 
were made with the view of finding, if possible, some 
rational explanation of great colliery explosions which up 
to that time appear to have baffled every attempt to 
grapple with them, and were not intended to form a kind 
of counterpart on the large scale of the exact eudiometric 
processes resorted to in the laboratory. At the same 
time I may state, however, that, so far as I have been able 
to ascertain by reading and observation, the methods 
then employed will compare not unfavourably, as regards 
exactness, with any that have succeeded them, not ex- 
cluding those of the Prussian Wetter-Commission. 
W. GALLOWAY 
THE FAUNA OF RUSSIAN CENTRAL ASIA 
Ui NTIL within the last thirty years Turkistan has been 
unknown to science, and what is now ascertained 
concerning its fauna and flora is for the most part inac- 
cessible to the scientific world because written in Russian. 
Not that autoptic writers of eminence upon the zoology of 
the country are numerous. They do not number a dozen, 
the names most conspicuous being Prjevalsky, Alpheraky, 
Bogdanoff, Severtsoff, and especially Fedchenko. _Prje- 
valsky’s routes do not touch mine, except in the Kuldja 
