1064 



VENTILATION OF MINES 



2077 



2079 



vented from passing directly through the thirling a, and is forced along the right- 

 hand side of the brattice, and, sweeping over the wall face or forehead, returns by 

 the back of the brattice, and passes through the thirling a. It is prevented, however, 

 from returning in its former direction by the brattice planted in the forehead c, where- 

 by it mounts up and accomplishes its return close to that forehead. Thus headways 

 and boards are ventilated till another thirling is made at the upper part of the pillar. 

 The thirling a is then closed by a brick stopping, and the brattice-boards removed 

 forward for a similar operation. 



When blowers occur in the roof, and force the strata down, so as to produce a large 

 vaulted excavation, the accumulated gas must be swept away ; because, after filling 

 that space, it would descend in an unmixed state under the common roof of the coal. 

 The manner of removing it is represented in jig. 2077, where a is the bed of coal, 

 b the blower, c the excavation left by the downfall of the roof, d is a passing door, 

 and e a brattice. By this arrangement the aerial current is carried close to the roof, 

 and constantly sweeps off or dilutes the inflammable gas of the blower, as fast as it 

 issues. The arrows show the direction of the current ; but for which, the accumu- 

 lating gas would be mixed in explosive proportions with the atmospheric air, and 

 destroy the miners. 



There is another modification of the ventilating system, where the air-courses are 

 traversed across ; that is, when one air-course is advanced at right angles to another, 

 and must pass it in order to ventilate the workings on the farther side. This is 

 accomplished on the plan shown in fig. 2078, where a is a main road with an air- 

 course, over which the other air-course b, has to pass. The sides of this air-channel 

 are built of bricks arched over, so as to be air-tight, and a gallery is driven in the 

 roof strata as shown in the figure. If an air-course, as a, be laid over with planks 

 made air-tight, crossing and recrossing may be effected with facility. The general 

 velocity of the air in these ventilating channels is from 3 to 4 feet per second, or about 



2 miles per hour, and their internal dimensions 

 vary from 5 to 6 feet square, affording an area of 

 from 25 to 36 square feet. 



The hydraulic air-pump deserves to be noticed 

 among the various ingenious contrivances for 

 ventilating mines, particularly when they are 

 of moderate extent, a is a large wooden tub, 

 nearly filled with water, through whose bottom 

 the ventilating pipe b passes down into the re- 

 cesses of the mine. Upon the top of b there is 

 a valve e, opening upwards. Over b, the gaso- 

 meter vessel is inverted in a, having a valve 

 also opening outwards at d. When this vessel 

 is depressed by any moving force the air con- 

 tained within it is expelled through d ; and when 

 it is raised, it diminishes the atmospherical pressure in the pipe b, and thus draws 

 air out of the mine into the gasometer ; which cannot return on account of the valve 

 at e, but is thrown out into the atmosphere through d at the next descent. 



Struvds Mine Ventilator. This ventilator has been constructed in some of the 

 mines of South Wales upon a very large scale. Although in principle a pump of the 

 simplest form, some of the pistons have been made 20 feet in diameter, and two 

 pumps were constructed 21 feet in diameter. See Jiff. 2080. 



In some mines to which the machine has been applied, the rarefaction and ventila- 

 tion has proved so strong as to prevent single doors being opened, unless protected 

 by supplemental doors. The circumstance of the air not being compressed in the 

 machine admits of large valve spaces, so that there is scarcely any appreciable 

 resistance to the passage of the air through the machine. 



The annexed drawing, fig. 2080, represents the machine in operation at the Governor 

 and Company's large collieries at Cwm Avon, Glamorganshire. 



The sectional view explains the internal construction, the darts showing the air- 

 currents ascending the upcast pit A, from the interior of the mine into the machine. 



The general plan of distributing the air in all cases is to send the first of the 

 current that descends in the downcast shaft among the horses in the stables, next 

 among the workmen in the foreheads, after which the air, loaded with whatever 

 mixtures it may have received, is made to traverse the old wastes. It then passes 

 through the furnace with all the inflammable gas it has collected, ascends the upcast 

 .shaft, and is dispersed into the atmosphere. This system, styled coursing the air, 

 was invented by Mr. Spedding of Cumberland. 



The piston B, is shown immersed in water, which forms an air-tight packing. 



The front or outlet valves B, are shown in the external view of the ventilator. The 





