The velocity of the transmission of explosion in gaseous mixtures is as characteristic a quantity for gaseous systems as the velocity of the transmission of sound. Berthelot showed that this velocity depends neither upon the pressure nor upon the size of the tubes in which the gaseous mixture is contained, nor upon the material out of which the tube is made. Dixon (1891) determined the magnitude of these velocities for various mixtures, and his results proved very near to those previously given by Berthelot. For comparison we give the velocities expressed in metres per second: +-----------------+-------+-----------+ | -- | Dixon | Berthelot | +-----------------+-------+-----------+ | H_{2} + O | 2,821 | 2,810 | | H_{2} + N_{2}O | 2,305 | 2,284 | | CH_{4} + 4O | 2,322 | 2,287 | | C_{2}H_{2} + 6O | 2,364 | 2,210 | | C_{2}H_{2} + 5O | 2,391 | 2,482 | | C_{2}N_{2} + 4O | 2,321 | 2,195 | +-----------------+-------+-----------+ The addition of oxygen to detonating gas lowers the velocity of the transmission of explosion almost as much as the introduction of nitrogen. An excess of hydrogen on the contrary raises the velocity of transmission. It is remarked that the explosion of mixtures of oxygen with marsh gas, ethylene and cyanogen is transmitted more quickly if the oxygen be taken in such a proportion that the carbon should burn to oxide of carbon, _i.e._ the velocity of the explosion is less if the oxygen be taken in sufficient quantity to form carbonic anhydride. Observations upon liquid and solid explosives (Berthelot) show that in this case the velocity of transmission of explosion is dependent upon the material of the tube. Thus the explosion of liquid nitro-methyl ether in glass tubes travels at the rate (in dependence upon the diam., from 1 mm.-45 mm.) of from 1,890 to 2,482 metres, and in tubes of Britannia metal (3 mm. in diam) at the rate of 1,230 metres. The harder the tube the greater the velocity of transmission of explosion. The following are the velocities for certain bodies: metres Nitro-glycerine 1,300 Dynamite 2,500 Nitro-mannite 7,700 Picric acid 6,500 In conclusion we may add that Mallard and Le Chatelier (1882) observed that in the explosion of a mixture of 1 volume of detonating gas with _n_ volumes of an inert gas, the pressure is approximately equal to 9·2-0·9_n_ atmospheres.