640 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



although now quite measurable, would probably be insufficient to 

 cause any self-heating of the inclosure. The temperature would re- 

 main at 450° C, which is well below the ignition temperature of the 

 combustible mixture, or the point at which a solid would attain even 

 incipient incandescence. 



It is therefore necessary to distinguish between two possible con- 

 ditions under which gaseous combustion may occur, namely: (1) 

 homogeneously, that is to say, equally throughout the system as a 

 whole, at temperatures below the ignition point, slowly and without 

 flame, and at temperatures above the ignition point, rapidly and with 

 flame; and (2) heterogeneously, or only in layers immediately in 

 contact with an incandescent surface (" surface" or " flameless" com- 

 bustion). Other things being equal, the heterogeneous surface com- 

 bustion is a faster process than the normal homogeneous combustion 

 of ordinary flames. 



The influence of hot surfaces upon combustion at low temperatures 

 seems to have occupied the attention of several chemists (Dulong and 

 Thenard and, independently, Dobereiner, in France, Sir Humphrey 

 Davy, William Henry, Thomas Graham, Faraday, and de la Rive, 

 in England) during the first third of the last century; but no one 

 of these distinguished men succeeded in evolving a satisfactory theory 

 of the phenomenon, nor, with the exception of the famous "Dobe- 

 reiner lamp," was there any practical outcome of their efforts. In 

 1836, after a long but abortive controversy between Faraday and 

 de la Eive, interest in the subject was dropped, not to be revived until 

 recent years. Prof. Bone's attention was first drawn to the subject 

 during the course of an investigation on the combustion of hydro- 

 carbons at low temperatures. The subject soon became so absorb- 

 ingly attractive that he embarked upon what proved to be a long 

 inquiry into the influence of a great variety of hot surfaces upon the 

 combination of hydrogen and oxygen at temperatures below the 

 ignition point. The inquiry has also included other cases of slow 

 combustion ; and experiments now in progress in his laboratory will 

 materially advance the science of the subject. 



Prof. Bone's experimental results justify the conclusion that the 

 power of accelerating gaseous combustion at temperatures below the 

 ignition point is possessed by all surfaces in varying degrees, de- 

 pendent upon their chemical characters and physical texture. More- 

 over, the " activity " of a given surface can be enhanced or diminished 

 at will in a truly marvelous manner by previous special treatment. 

 Thus, for example, in the case of the combination of either hydrogen 

 or carbon monoxide with oxygen, in contact with a nonoxidizable 

 metal or nonreducible oxide, the " activity " of the surface may be 

 greatly stimulated by previous contact with the combustible gas, and, 



