22 Experimenis and Observations 
greatest heat is in the centre of the explosive mixture. In 
looking steadfastly at flame, the part where the combustible mat- 
ter is volatilized is seen, and it appears dark, contrasted with the 
part in which it begins to burn, that is where it is so mixed with 
air as to hecome explosive. The heat diminishes towards the 
top of the flame, because in this part the quantity of oxygen is 
least. When the wick increases to a considerable size from 
collecting charcoal, it cools the flame by radiation, and prevents 
a proper quantity of air from mixing with its central part ; in 
consequence, the charcoal thrown off from the top of the flame 
is only red hot, and the greater part of it escapes unconsumed. 
The intensity of the light of flames in the atmosphere is in- 
creased by condensation, and diminished by rarefaction, appa- 
rently in a higher ratio than their heat; more particles capable 
of emitting light exist in the denser atmospheres, and yet most 
of these particles, in becoming capable of emitting light, absorb 
heat; which could not be the case in the condensation of a pure 
supporting medium. 
The facts stated in Section I. show that the luminous appear- 
ances of shooting stars and meteors cannot be owing to any in- 
flammation of elastic fluids, but must depend upon the ignition 
of solid bodies. Dr. Halley calculated the height of a meteor 
at ninety miles, and the great American meteor which threw 
down showers of stones was estimated at seventeen miles high. 
The velocity of motion of these bodies must in all cases be im- 
mensely great, and the heat produced by the compression of the 
most rarefied air from the velocity of motion must be probably 
sufficient to ignite the mass; and all the phenomena may be 
explained, if falling stars be supposed to he small solid bodies 
moving round the earth in very eccentric orbits, which become 
ignited only when they pass with immense velocity through the 
upper regions of the atmosphere, and if the meteoric bodies which 
throw dewn stones with explosions be supposed to be similar 
bodies which contain either combustible or elastic matter. 
Cobham-hall, Kent, Jan. 8, 1817. 
SF 
Some new Experiments and Observations on ihe Combustion of 
Gaseous Mixtures, &c. 
In a paper read before the Royal Society at their last two 
meetings, I have described the phenomena of the slow com- 
bustion of hydrogen and olefiant gas without flame. In the same 
paper I have shown, that the temperature of flame is infinitely 
higher than that necessary for the ignition of solid bodies. It 
appeared to me, therefore, probable, that in certain combinations 
of gaseous bodies, for instance, those above referred to, when 
the 
