1060 VENTILATION OF MINES 



VENETIAN" "WHITE. A carefully-prepared carbonate of lead. See WHITE LHAD. 

 VENICE TURPENTINE. A turpentine obtained from the larch (Larix 

 Europtea). 



VENTIIiATION OF MINES. In our subterranean operations, especially 

 where quantities of carbonic acid are constantly being produced by respiration and 

 combustion, and where, as especially in our coal-mines, the workmen are constantly 

 exposed to the efflux of a gas light carburetted hydrogen, which, when mixed with 

 air, becomes explosive, it is necessary to adopt the means of removing, as rapidly as 

 possible, the atmosphere by which the miner is surrounded. 



The production of noxious gases renders ventilation a primary object in the 

 system of mining. If an air-pipe has been carried down the engine pit for the purpose 

 of ventilation in the sinking, other pipes are connected with it, and laid along the 

 pavement, or are attached to an angle of the mine next the roof. These pipt are 

 prolonged with the galleries, by which means the air at the forehead is drawn up the 

 pipes and replaced by atmospheric air, which descends by the shaft in an equable cur- 

 rent, regulated by the draught of the furnace at the pit-mouth. This circulation is 

 continued till the miners cut through upon the second shaft, when the air-pipes become 

 superfluous ; for it is well known that the instant such communication is made, as is 

 represented in fig. 2068 a, the air spontaneously descends in the engine-pit A, and passing 

 along the gallery a, ascends in a steady current in the second 

 2068 a pit Bi The air, in sinking through A, has at first the atmospheric 



temperature, which in winter may be at or under the freezing- 

 point of water ; but its temperature increases in passing down 

 through the relatively warmer earth, and ascends in the shaft B, 

 warmer than the atmosphere. When shafts are of unequal 

 depths, as represented in the figure, the current of air flows 

 pretty uniformly in one direction. If the second shaft has the 

 same depth with the first, and the bottom and mouth of both be in the same horizontal 

 plane, the air would sometimes remain at rest, as water would do in an inverted 

 syphon, and at other times would circulate down one pit and up another, not always in 

 the same direction, but sometimes up the one and sometimes up the other, according 

 to the variations of temperature at the surface, and the barometrical pressures, as 

 modified by winds. There is in mines a proper heat, proportional to their depth, in- 

 creasing about one degree of Fahrenheit's scale for every 50 feet of descent. 



There is a simple mode of conducting air from the pit-bottom to the forehead of the 

 mine, by cutting a ragglin, or trumpeting, as it is termed, in the side of the gallery, as 

 2069 represented in fig. 2069, where A exhibits the gallery in the coal, 



and B the ragglin, which is from 15 to 18 inches square. The coal 



itself forms three sides of the air-pipe, and the fourth is composed of 

 thin deals applied air-tight, and nailed to small props of wood fixed 

 between the top and bottom of the lips of the ragglin. This mode is very generally 

 adopted in running galleries of communication, and dip-head level galleries, where 

 carbonic acid abounds, or when from the stagnation of the air the miners' lights 

 burn dimly. 



When the ragglin or air-pipes are not made spontaneously active, the air is some- 

 times impelled through them by means of ventilating-fanners, having their tube placed 

 at the pit-bottom, while the vanes are driven with great velocity by a wheel and 

 pinion worked with the hand. In other cases, large bellows like those of the black- 

 smith, furnished with a wide nozzle, are made to act in a similar way with the fanners. 

 But these are merely temporary expedients for small mines. 



Ventilation of mines and collieries has been likewise effected on a small scale, by 

 attaching a horizontal funnel to the top of air-pipes elevated a considerable height 

 above the pit-mouth. The funnel revolves on a pivot, and by its tail-piece places its 

 mouth so as to receive the wind. At other times, a circulation of air is produced by 

 placing coal-fires in iron grates, either at the bottom of an upcast pit, or suspended 

 by a chain a few fathoms down. 



In all great coal-mines the aerial circulation is regulated and directed by double 

 doors, called main or bearing doors. These are true air-valves, which prevent the 

 current of air moving in one direction from mixing with another moving in a different 

 direction. Such valves are placed on the main roads and passages. Their functions 

 are represented in the annexed ./i*?. 2070 : where A shows the downcast shaft, in which 

 the aerial current is made to descend ; B is the upcast shaft, sunk towards the rise of 

 the coal ; and c the dip-head level. Were the mine here figured to be worked without 

 any attention to the circulation, the air would flow down the pit A, and proceed in a 

 direct line up the rise mine to the shaft B, in which it would ascend. The consequence 

 would therefore be, that all the galleries and boards to the dip of the pit A, and those 

 lying on ench side of the pits, would hare no circulation of air; or, in the language 



