454 Proceedings of Philosophical Societies. [Dxc. 
This is ‘characteristic of carbureted hydrogen, as both Mr. Dalton 
and myself have ascertained. He found the specific gravity to be 
0°639, but his specimen was mixed with common air. I have 
shown the true specific gravity of this gas to be 0°555 ee nan 
Memoirs, i. 508). 
He found it much less combustible than other combustible gases, 
Tron heated to whiteness does not set it on fire. It requires actual 
flame. This fact has induced him to propose a lantern made air- 
tight, with a hole below to admit air, and one above to act as a 
chimney, as a complete security against the explosion of the fire~ 
damp in coal-mines. He found that when a mixture of common 
air and carbureted hydrogen gas, in such proportions as to explode, 
is let up into such a lantern, the flame increases, so as nearly to fill 
the lantern, and then the lamp goes out. He conceives that when- 
ever in a coal-mine the air is mixed with carbureted hydrogen to 
the exploding point, that such lamps would go out, and no explo- 
sion would follow. But such an experiment would be very hazard- 
ous. The fact is, that in such a case the gas within the Jantern 
burns, and of course extinguishes the lamp; but in all probability 
the gaseous combustion would extend itself through the holes in the 
lantern, which are filled with gas at the exploding point, and set 
fire to the whole mixture in the mine. This would certainly 
happen sometimes, if not always; so that the lantern of Davy 
would furnish no certain security to the miners. ‘The lamp of Dr. 
Clanny, if properly improved, is a much safer contrivance, and 
might be made equally cheap. 
IT ascertained that the limits of the explosion of this gas were 12 
volumes of air and one of gas, and six volumes of air and one of 
gas. As far as I could understand Sir H. Davy’s experiments, they 
led nearly to the same result. He succeeded in exploding a mixture 
of this gas and common air by electricity. I could not succeed in 
this, not having, it seems, hit upon the exploding proportions, 
though I tried a great many between the two limits. 
Sir H. Davy constructed likewise lanterns with valves to prevent 
the escape of gas from the lantern when it explodes. This would 
certainly render the lantern safe, provided it can be constructed so 
as to allow the lamp to burn. 
On Thursday, Nov. 16, an appendix to Sir Humpbry Davy’s 
paper was read, He found that the addition of 4th of*carbonic 
acid or of azote to the ne mixture of fire-damp and air pre- 
vented the explosion. 
- A paper by Mr, Daniel on Solutions was likewise partly read, 
When an amorphous mass of alum was left for some. weeks in water 
it assumed a pyramidal form, and the lower part of it was embossed 
by distinct octahedral crystals. Borax exhibited a similar appear- 
ance; the lower part was embossed with rhomboidal erystals. Mr. 
Daniel conceives that in these cases the cohesion of the solid re~ 
sisted unequally the solvent power of the liquid, and that the upper 
part of the liquid aeted more powerfully than the lower, Hence 
