Experiments on the Transmission of Explosions. 19 



command to fire, quickly turned on the taps T and S. A 

 second observer, placed opposite DF, thereupon broke the 

 primary circuit of the coil, producing a spark in EC, and at 

 the same time closely watched DF for any flash indicating 

 that the mixture in B had been fired across the air gap by 

 the explosion in A. 



Though the glass tube DF was very strong, it was found 

 necessary to wrap wire gauze around it, inasmuch as it 

 was several times shivered to pieces by the violence of the 

 explosion-wave. Though the glass tubes employed between 

 A and B were frequently comparatively weak, experience 

 showed that the pressure produced by the explosion against 

 the wall of the tube X was so small, that the tube was in 

 no case burst. 



First Series of Experiments. — A number of experi- 

 ments were made with glass tubing of 20 mm. internal 

 diameter of various lengths. After fixing the glass tube 

 by means of Faraday's cement to the two brass junctions, 

 the distance from the centre of the tap T to the centre of 

 the tap S was measured. Only these experiments in which 

 this distance TS is exactly the same, are made under the 

 same conditions: it is not sufficient to make experiments 

 with a particular tube of say 200 mm. length at one time, 

 and again at a subsequent period, without making sure that 

 the tube is fixed on to the brass pieces in the same manner. 

 Differences in the length of TS with the same glass tube 

 to the extent of 10-15 mm. may easily occur, which subse- 

 quent experiments will show to be very important. We 

 shall therefore class experiments according to the length of 

 TS. The volume of the air-gap was determined in each 

 case by titration with water. 



(1) TS = 283 mm. Vol. of air-gap 73 cc. 



The flash produced by the explosion in A traversed the 

 whole length of X, but the mixture in B was not fired. 

 6 experiments made, with the same results. 



