Some new Researches on Flame. 13 
Mr. Leslie, in his elaborate and ingenious researches on heat, 
has observed the high powers of hydrogen of abstracting heat 
from solid bodies, as compared with that of common air and 
oxygen. I made a few experiments on the comparison of the 
powers of hydrogen, in this respect, with those of carburetted 
hydrogen, azote, oxygen, 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 olefant gas, coal gas, carbonic acid gas, chlorine, 
nitrous oxide gas, hydrogen, oxygen, azote, and air, at equal 
temperatures, 32° Fahrenheit. 
The times required for cooling to 106° were for 
Air Be eee ake it BOT eh One « tiie nih oir {-47 
Hydrogen ©.» -. “49 Nitrous oxide®¥ » 2. 2°30°2°53 
Olefiant gas .. +. Trio Carbonic acid gas* 2°45 
Coal gas ee 5a et ealopine ti Rate 3°6 
Azote oe Haan See 
It appears from these experiments, that the power of elastic 
fuids to abstract or conduct away heat from solid surfaces, is in 
some inverse ratio to their density, and that there is something 
in the constitution of the light gases, which enables them to 
carry off heat from solid surfaces in a different manner from that 
in which they would abstract it in gascous mixtures, depending 
probably upon the mobility of their parts 7. The heating of 
gaseous media by the contact of fluid or solid bodies, as has been 
shown by Count Rumford, depends principally upon the change 
of place of their particles; and it is evident from the results 
stated in the beginning of this section, that these particles have 
different powers of abstracting heat analogous to the different 
powers of solids and fluids. Where an elastic fluid exerts a 
cooling influence on a solid surface, the effect must depend prin- 
cipally upon the rapidity with which its particles change their 
places: but where the cooling particles are mixed throughout a 
mass with other gaseofis particles, their effect must principally 
depend upon the power they possess of rapidly abstracting heat 
from the contiguous particles; and this will depend probably 
upon two causes, the simple abstracting power by which they 
become quickly heated, and their capacity for heat, which is great 
jn proportion as their temperatures are less raised by this abs- 
traction. 
* These two last results were observed by Mr. Faraday of the Royal In- 
stitution, (from whom I receive much oseful assistance in most of my ex- 
criments,) when [ was absent from the Laboratory. 
+ Those particles which are lizhtest must be couceived most capable of 
ebanying place, and would therefore cool solid surfaces most rapidly: in 
the cooling of gaseous mixtures, the mobility of the particles can be of lit- 
tle consequence, 
. Whatever 
