I/O Mr. B. Lean and Mr. H, B. Dixon on 



closed by a massive steel tap, the bore of which was also 

 15 mm. in diameter; this tap carried a by-pass. At the 

 other end was a firing-piece closed by a steel tap. The 

 length of the column of explosive gases in the case of the 

 above tube was 73-5 cm. 



The explosive mixture was made and stored in an iron 

 gas-holder over water. To fill the tube, the tap was con- 

 nected with the gas-holder, and the air in the tube expelled 

 through the by-pass. In every case, one-tenth of a cubic 

 foot was sent through the tube, before the taps were closed, 

 so as to ensure the removal of all air. After every explosion, 

 the products were expelled by a current of air before re- 

 filling. 



The flash had to travel 6 cm. before it could be seen 

 beyond the end of the steel tap. 



To this steel tap glass tubes could be attached by means 

 of cement. They had the same internal diameter as the 

 brass firing tube. Four different lengths were employed : — 



tube b ; length of air column 36-0 cm. 



j> ^ )) )) "9 " 



)) <* !) )) -^55 " 



„ e „ „ 240 „ 



Experiments were also made in which no glass tube 

 was attached. These we may class under the letter a : in 

 these the length of the air column was 6 cm. The point 

 which the flash reached was noted by the eye : with 

 practice this could be done within i centimeter. In every 

 case 10 experiments were made under precisely the same 

 conditions : such large differences were found between the 

 results of similar experiments, that unless the mean of a 

 considerable number had been taken, it would have been 

 impossible to arrive at any generalisation. 



With each mixture of coal-gas and air experiments were 

 made with several lengths of glass tubing attached to the 

 firing tube. 



