1889.] 



Ignition of an explosive Gaseous Mixture. 



451 



The chief portion of the paper is occupied by a description of the 

 details of the precautions taken to make the measurements as accurate 

 as possible. 



II. " An Experimental Investigation of the Circumstances under 

 which a Change of the Velocity in the Propagation of the 

 Ignition of an Explosive Gaseous Mixture takes place in 

 closed and open Vessels. Part I. Chronographic Measure- 

 ments." By FREDERICK J. SMITH, M.A., Millard Lecturer, 

 Exptl. Mech., Trin. Coll., Oxford. Communicated by A. G. 

 VERNON HARCOURT, F.R.S. Received March 12, 1889. 



(Abstract.) 



The subject of the paper of which this is an abstract, is the deter- 

 mination of the rate of change of the velocity of the propagation of 

 an explosion in gaseous explosive mixtures. 



It has been noticed by several investigators, viz., MM. Berthelot 

 and Vielle, MM. Mallard and Le Chatelier, and Professor H\ B. Dixon, 

 F.R.S., that explosive gaseous mixtures after ignition do not reach 

 their maximum velocity of propagation at once, but that a certain 

 maximum velocity is attained soon after initial ignition. 



In order to investigate this interesting period, which may be called 

 the acceleration period of an explosion, chronographic measurements 

 of a peculiar nature were found necessary. 



It was at once evident that but little advance in this branch of the 

 subject of explosions could be made unless exceedingly minute periods 

 of time could be measured with certainty. 



