4 Dixon & Lowe, Experiments on Abel's theory. 



laboratory and on the larger scale, in order to confirm or 

 disprove the observations on which Abel founded his 

 conclusions. 



Both the experiments made by Abel and the con- 

 clusions he has drawn from them appeared open to 

 criticism. When gas and air entering by separate 

 pipes are drawn along a gallery a considerable time 

 must elapse before there is complete mixture of the 

 gas and air. Abel states that special precautions were 

 taken to ensure mixture, and that analyses of samples 

 taken at different places in the gallery proved that 

 the mixture was complete. But from the description of 

 the apparatus used it would appear that Abel depended 

 on the length of " run " — about i6 feet— to bring about 

 admixture. Now with a very rapid current the mixture 

 might seem to be complete since the analysis of samples 

 collected at the top and bottom of the gallery might be 

 identical, but, nevertheless, the mixture might not be 

 really homogeneous but streaky. In the experiments made 

 at Eskmeals,with a gallery practically the same as Abel's, 

 this was found to be the case. The "flares" produced in 

 such a mixture were totally different from those formed 

 when the gas and air had been thoroughly stirred together 

 by being pulled through a sirocco fan. In the streaky 

 mixture the flares were almost noiseless. They had very 

 little charring effect and the discontinuity of the flame 

 was evident ; in the homogeneous mixture the flares 

 became roaring flames, charring wood immediately. 



With less rapid air-currents the lighter gas flowed 

 upwards and passed along the top of the gallery. A 

 lamp-flame below only showed a small cap, while the 

 mixture, a few inches above the flame, was explosive. 

 The admission of dust to such a stream of gas and air 

 might cause ignition of the mixture above if a particle of 



