... when B. before C. until D. sinceIII. AProfessor Meredith Thring, Professor of Mechanical Engineering at Queen MaryCollege, London showed off his latest invention to the Press yesterday. It ... ideas of mechanical mining to previous Chairmen of theBoard but each time nothing has happened,” he said. “The Board are not thinking enoughabout the future. My latest idea would put the cost of ... the present cost of supplying fresh air to mines,“ said Professor Thring.“there need be no oxygen present, and this would mean there would be no risk of explosions.”The Professor does his economic...