Manchester Memoirs, Vol. Ivii. (191 3), No. 15. 7 



out to a narrow jet. Dust could be placed in the bottom 

 of the tube, and on introducing the gas it was blown 

 about in the form of a light cloud. Through the cork 

 two brass wires were in.serted, by means of which an 

 electric discharge could be passed at any point in the 

 tube. A hole was also bored in the cork as an exit for 

 the gas, and was left open during all the experiments. 



A mixture of 15% of Manchester coal-gas with 85% 

 of air was made and stored in a gasholder over water. 

 A portion was passed into the apparatus and an electric 

 discharge passed between the brass wires. The gas 

 exploded violently and the cork was blown out. In the 

 next experiment magnesia dust was introduced, the gas 

 blown in and exploded as before. In this case a yellow 

 flame was produced instead of a blue one, but no other 

 difference was observed. 



Nine per cent, coal-gas sparked near the bottom of 

 the tube is immediately burnt up, but when sparked near 

 the top of the tube the flame slowly travels downwards, 

 with a peculiar "jelly-fish" flame at a rate of several cm. 

 per second. The introduction of dust only made the 

 flame more luminous, but did not otherwise affect it. 



Eight per cent, of gas sparked at the bottom of the 

 tube was burned completely, but the flame would not 

 travel downwards when sparked at the top. The same 

 facts were observed when dust was present. 



Seven per cent, of gas behaved similarly to 8 % in all 

 particulars. 



Six per cent, appeared on the lower limit of explosive- 

 ness, often not exploding with the first spark, but only 

 after two or three discharges. Dust did not make it 

 explode any more easily or more frequently. 



These experiments show conclusively that on the 

 small scale at least the presence of calcined magnesia 



