74 Professor William Arthur Bone [Feb. 28, 



flameless combustion, and he himself was led to ask whether, seeing 

 that the temperatures of flames far exceed those at which solids 

 become incandescent, a metallic wire can be raised to incandescence 

 l)y the slow combustion of two p:ases " without actual flame, but pro- 

 ducing heat enough to keep the wire ignited." In this way he 

 discovered the remarkable property of platinum and other metallic 

 wires of inducing surface comlmstion, and in the course of his further 

 experiments on this subject, he made two notable observations 

 respecting the burning of compounds containing carbon and hydro- 

 gen. He found " much carbonic oxide " produced when a platinum 

 wire was kept incandescent by the slow combustion of a mixture of 

 ethylene and oxygen, rendered non-explosive by an excess of the 

 hydrocarbon, and in a similar experiment with ether vapour, he 

 recorded the appearance of " a pale phosphorescent light " accom- 

 panied by " the formation of a peculiar acrid volatile substance 

 possessed of acid properties." 



Finally, in speculating upon the diflicult and thorny subject of the 

 luminosity of hydrocarbon flames, he was " led to imagine " that it 

 " might be owing to the decomposition of part of the gas towards the 

 interior of the flame where the air was in smallest quantity, and the 

 deposition of solid charcoal, which, first by its ignition, and afterwards 

 by its combustion, increased in a high degree the intensity of the 

 light." It is important to observe that not only did Davy rightly 

 attribute the luminosity of a hydrocarbon flame to the presence therein 

 of incandescent carbon, but also that he avoided the error of attribut- 

 ing the separation of carl)on to a supposed preferential burning of 

 hydrogen. 



In considering the propagation of a flame through an explosive 

 mixture of gases, it is necessary to distinguish between two well- 

 defined conditions. When such a mixture is ignited, the flame travels 

 for a certain limited distance (a few feet only) at a fairly uniform 

 slow velocity, which in the case of a mixture of hydrogen and oxygen 

 in their combining ratios is approximately o4 metres (08 yards) per 

 second. This initial stage of the combustion is called " inflammation.'' 



After traversing a few feet, however, the flame begins to vibrate 

 and alters in character. The vibrations become more and more 

 intense, the flame swinging l)ackwards and forwards with oscillations 

 of increasing ampUtude. Then one or other of two things happens ; 

 either the flame is extinguished, or it goes forward with an exceedingly 

 great and constant velocity, producing the most violent effects. The 

 new condition thus set up is termed " Detonation,'' and the forward 

 movement of the flame is called the " Explosion Wave." 



The discovery of " tletonation " in gaseous mixtures was made 

 simultaneously by M. Berthelot and MM. Malard and Le Chatelier, 

 in the year 18S1 ; Berthelot proved that the velocity of the explosion 

 wave is independent of the length of the column of gas traversed, and 



