60 Sir H. Davy’s researches on flame. 
show sufficiently, if the conclusions of M. M. De la Roche 
and Berard be correct, that other causes, besides density and 
capacity for heat, interfere with the phenomena. Thus 
nitrous oxide, which is nearly -§• denser than oxygene, and 
which, according to De la Roche and Berard, has a greater 
capacity for heat in the ratio of 1.3503 to .97 65 in volume, 
has lower powers of preventing explosion; and hydrogene, 
which is 15 times lighter than oxygene, and which in equal 
volumes has a smaller capacity for heat, certainly has a higher 
power of preventing explosion ; and olefiant gas exceeds all 
other gaseous substances in a much higher ratio than could 
have been expected from its density and capacity. The ole- 
fiant gas I used was recently made, and might have contained 
some vapour of ether, and the nitrous oxide was mixed with 
some azote, but these slight causes could not have interfered 
with the results to any considerable extent. 
Mr. Leslie, in his elaborate and ingenious researches on 
heat, has observed the high powers of hydrogene of abstract- 
ing heat from solid bodies, as compared with that of common 
air and oxygene. I made a few experiments on the compa- 
rison of the powers of hydrogene, in this respect, with those of 
carburetted hydrogene, azote, oxygene, olefiant gas, nitrous 
oxide, chlorine, and carbonic acid gas. The same thermometer 
raised to the same temperature, 160°, was exposed to equal 
volumes (21 cubic inches) of olefiant gas, coal gas, carbonic 
acid gas, chlorine, nitrous oxide gas, hydrogene, oxygene, 
azote, and air, at equal temperatures, 52 0 Fahrenheit. 
The times required for cooling to 106° were for 
Air 2 
Hydrogene 45 - 
