Experiments on the Transmission of Explosions. 21 



Second Series of Experiments. — A number of 

 experiments were next made employing much narrower 

 tubing to enclose the air-gap, viz., 8-8^ mm. internal 

 diameter, instead of 20 mm., as in the former experiments. 



(1) TS = 275 mm. Air-gap 17*5 cc. Internal diam. 8*5 mm. 



B fired. 3 experiments. 



(2) TS = 389 mm. Air-gap 27 cc. Bore 8*5 mm. 



B fired. 4 experiments. 



(3) TS = 532 mm. Air-gap 32^ cc. Bore 8 '5 mm. 



B fired. 4 experiments. 



(4) TS = 588mm. Air-gap 31^ cc. Bore 8"o mm. 



B fired. 4 experiments. 



(5) TS = 665 mm. Air-gap 38*2 cc. Bore 8*o mm. 



B not fired. 3 experiments. 



(6) TS = 656mm. Air-gap 37*6 cc. Bore 8 - o mm. 



B fired. 2 experiments. 



(7) TS = 663 mm. Air-gap 38*1 cc. Bore 8 - o mm. 



B not fired. 2 experiments. 

 Thus the limit is found between (6) and (7). 



We can now advantageously compare the main results 

 of these two series of experiments. 



In series (1). 



If TS =196 mm., and air gap = 447 cc, B is not fired. 



If TS= 192 mm., and air gap = 43-0 cc, B is fired. 

 In series (2). 



If TS = 663 mm., and air gap = 38*1 cc, B is not fired. 



If TS = 656 mm., and air gap = 37*6 cc, B is fired. 



It would appear, therefore, that the question as to 

 whether B shall be fired by A through a given air gap, 

 depends upon the volume of air interposed, rather than 

 upon the length of the column of air. 



To test this conclusion a bulb was blown upon a 



portion of the glass tubing (bore 8 - o mm.) used in series 



No. 2, and this was substituted for 



a plane glass tube between the two 



brass junctions. 



