1915] 



on Gaseous Explosions 



285 



Fig. 15 is a rig-hfc-angle card taken bj Dr. Watson from a petrol 

 engine running at a high velocity. In that card the explosion period 

 is ofo of '^ second; and, assuming the flame to travel 4 inches before 

 striking the walls, the velocity of the flame is 90 feet per second. It 

 was well understood that the flame velocity was higher in engines, than 

 in closed vessels, and mechanical disturbance was assumed, but the 

 mechanical disturbance was believed to be that due to the admission 

 of the flame and the projection into the mass as a jet. Early in 



7. Relation of spark 



advance to fuel 

 efficiency 



8. High speed with 



coil ignition 



4a. Spark over inlet 



valve 

 ib. Spark over exhaust 



valve 

 4c. Both sparks together 



5a. Spark over inlet 



valve 

 56. Both sparks together 

 6. Fixed and variable 



ignition point 



Fig. 15. 



1912, simultaneous experiments were made by Clerk and Hopkinson 

 by different methods to determine the nature of the mechanical 

 disturbance causing this increase of rate. Clerk's experiments were 

 made with the engine shown in Fig. 13. This figure shows vertical 

 and horizontal sections. The engine was fitted with trip gear, which 

 enabled a charge to be taken in, compressed and expanded for any 

 desired number of cycles without ignition and ignited under com- 

 pression, when the desired number of alternate compressions and 

 expansions had been completed. The object of the experiments was 

 to compare the rate of inflammation ignition immediately after 

 Vol. XXL (No. 109) u 



