236 Scientific Intelligence. [Sepr. 
 X. Combustion of Carbureted Hydrogen Gas. 
I have been requested to explain why the steel-mills, as they are 
called (which consist of a piece of steel rubbing against a kind of 
grind-stone, and emitting a prodigious number of sparks,) do not 
set fire to a mixture of carbureted hydrogen gas and common air. 
It is not easy to assign a very satisfactory reason. ‘The heat of the 
sparks is certainly sufficient for the purpose ; for if you collect them 
you find them in globules that have undergone fusion. Now the 
black oxide of iron will not melt, except at a much higher tempe- 
rature than is sufficient to set fire to such a mixture. I never was 
able to burn a mixture of carbureted hydrogen gas and common air 
by passing electric sparks through it ; but if you bring a red-hot 
bar of iron in contact with the mixture, it fires immediately, These 
facts induce me to suspect that the effect depends upon the size of 
the ignited body, A very small spark is probably not capable of 
impelling a sufficient number of particles of oxygen against a par- 
ticle of carbureted hydrogen to produce instant combination, which 
I conceive occasions the combustion. Sometimes it is well known 
that the mixture is exploded by the steel-mills. In such eases, I 
conceive, the sparks are uncommonly large. 
XI. Another Accident at a Coal-Mine near Newcastle. 
On Monday, the 31st of July, another melancholy accident hap- 
pened at Messrs. Nesham and Co.’s colliery, at Newbottle, in the 
county of Durham. The proprietors had provided a powerful loco- 
motive steam-engine, for the purpose of drawing 10 or 12 coal- 
waggons to the staith at one time; and Monday being the day it 
was to be put in motion, a great number of persons belonging to the 
colliery had collected to see it; but unfortunately, just as it was 
going off, the boiler of the machine burst. ‘the engine-man was 
dashed to pieces, and his mangled remains blown 114 yards; the 
top of the boiler (nine feet square, weight 19 cwt.) was blown 100 
-yards ; and the two cylinders 90 yards. A little boy was also thrown 
to a great distance. By this accident 57 persons were killed and 
wounded, of whom I! were dead on Sunday night, and several 
yemain dangerously ill. The cause of the accident is accounted for 
as follows ; the engine-man said, “ as there were severa] owners and 
viewers there, he would make her (the engine) go in grand stile,” 
and he had got upon the boiler to loose the screw of the safety 
valve, but being overheated, it unfortunately exploded. It will be 
recollected, that at the fatal blast which recently took place at this 
colliery, the first who arrived at the bank, holding by a rope, was a 
little boy, about six or seven years of age. The poor little fellow is 
among the number dead, , 
XII. Carbonate of Bismuth. 
A new species of ore has been lately discovered in Cornwall, the 
