DOBSON ENQUIRY

Greymouth Evening Star, 23 July 1927, Page 12

DOBSON ENQUIRY

(To the Editor.) Sir, -Kindly allow me space to. reply to Mr. Ward’s letter ot the 22nd inst, which is a little confusing He says that I must admit a greater foi(L was generated in the mine than was expended in the intake and upcast drives'. How he arrives at his state ment is so far only known to lumseK, as greater destruction was don without than within the seat ot the ex plosion. How he can define the line ot least resistance to the upcast sha , and account on the + as « iSt T??rt o fan with a velocity ot about 13ft per second, and a motive column as ta. as natural ventilation is concerned of practically nill, and the two enhances being practically on the same altitude, and the fan only Sivmg •> difference in pressure ot about 51hs. ner square inch, which would be an insignificant factor vrfhen you deai with explosive forces of many thousands of lbs per square inch. Now to show you where Mr. Ward is wrong No explosion can exist without oxygen. In a return airway we would have an atmosphere of oxygen and diffiused gases. But in the intake airway we have only the pure atmosphere and it is taught even to the ordinary day school boy that in any explosion the greater force and extension is always in the direction which is being assisted by the most liberal supply of oxygen which in this case was the intake airway. Mr. Ward has not set forth any theory as to these men being found alive, but he tries to tell_ us that a greater force passed over these men than went up the stone drives in which he states hurled mine tubs a distance of twelve chains which we already know. Now a Dobson mine tub weighs approximately when empty 800 lbs., and the average man, say IGOlbs. The area of a man’s body in proportion to his weight would be about equal in resistance to the mine tubs, against the explosive forces, but he says the force was greater so why is it that the men were found alive in their respective places instead of being delivered to the same destination as the mine tubs but with greater velocity, through the greater force being applied to them. I don’t see what the destination of the mine materia', blackberries or Dobson monument has got to do with coal dust theory or his reverse theory to the Brunner and Dobson Explosion Commission. I have already stated why the destruction could be greater at the bottom of the dip than at the top, as he states was the case in Brunner, because the adjacent surroundings of the seat of the explosion was deficient of sufficient explosive material to propagate its force of violence any further and spent in to the goof which he says was in the rise workings which was to an advantage. As for blown out shots, they do occur if the shot is not properly made, but they differ very materially. I have already stated that an explosion from a blown out shot will occur when finely divided particles of coal dust of sufficient quan lily is raised in a cloud of air and coining in contact with a flame of sufficient heat and duration to cause ignition of the inflammable mixture. Yours etc., — E. W. KENNEDY, Runanga.