Captain FABERasked the Homo Secretary if, in the case of new collieries, he will consider the advisability of the upcast shaft being made larger than the downcast, seeing that as air passes through a mine it increases in volume and in the event of an explosion the smaller shaft is wrecked from too little size to take the coal dust and air?
§ Mr. CHURCHILLI am informed by my expert advisers that it is considered good mining practice to make the diameter of the upcast shaft greater than that of the downcast. The expansion of the air, however, due to the temperature of the mine, is not of much importance except in the case of mines ventilated by an underground furnace—a method now seldom used—where the heat of the fire-largely increases the volume of the air besides adding to it the products of combustion. In most coal mines the air is now drawn through the workings and up the upcast shaft by means of fans placed at the surface and the increase in its volume is insignificant. Moreover, in many mines the upcast shaft is not habitually used for winding persons or minerals, and, being, therefore less obstructed than the downcast, it has a greater net size. The wrecking of an upcast shaft in the event of an explosion would not depend on its dimensions relatively to those of the downcast shaft, but (1) on whether the 1331W explosive blast enters the return airway, and if so (2) on the absolute size of the upcast and the obstruction encountered by the blast. To make the upcast shaft larger than the downcast would not therefore prevent its wreckage; and in the great mining disasters of recent years it has been the downcast shaft that has suffered most owing to the fact that the explosions have been carried along the intake airways (on haulage roads) by the coal dust.