M I N E. 



367 



Fit* mined 

 upwards. 



Blowers- 



face, or forehead, returns by the back of the brattice, 

 then passe* through the thirling n; but is prevented 

 from returning in it- former direction by the brattice 

 placed in the forehead c, by which it ascends, and makes 

 the return close to that forehead. In this manner 

 headways and boards are ventilated until another thir- 

 ling is made at the upper part of the pillar, when the 

 thirling a is closed by a brick stopping, and the brat- 

 tices removed and carried forward for a similar opera- 

 tion. 



Blind pit> If a blind pit or stapple has to be sunk from one coal 

 to another, or to regain a coal upon the other side of 

 a slip, the ingoing current of air must be carried to the 

 side of the pit, and conducted down one side of a brat- 

 tice, which is lengthened progressively as the pit grows 

 deeper, and the circulation or return air passes up the 

 other side of the pit, by which the rubbish is drawn 

 up, the brattice is carried down close to the pavement, 

 after which the coal is opened up with double headways 

 courses in the manner as before described. 



Sometimes pits have to be mined upwards, in which 

 case the inflammable air, from its specific lightness, 

 keeps always about the beads of the workmen. The 

 circulation is produced in this case by a brattice carried 

 up the shaft to produce a current of ingoing and re- 

 turning air, exactly the inverse of the above. 



When blowers occur in the roof, and force down the 

 strata, so as to produce a large vaulted cavity, it is ne- 

 cessary to sweep away the accumulated gas, which 

 would not only lodge in the cavity, but would de- 

 scend in an undiluted state under the common roof 

 of the coal. The mode of doing this is represented, 

 PLATE r ' '* where a is the bed of coal, b the blower, c the 

 cccxciti. cavity formed by the falling of the roof strata, d is a 

 fig. n. passing door, and e the brattice ; by this plan the cur- 

 rent of air is carried close to the roof, and constantly 

 sweeps away and dilutes the inflammable air of the 

 blower aa fait as it issues. The arrows shew the direc- 

 tion of the current ; were it not for this direction of the 

 ventilation, the accumulated gas would mix with the 

 current of common air, and produce an explodeable 

 mixture. The gas issuing from blowers is sometimes 

 conducted in pipes into other air courses, where the air 

 is returning to the upcast shaft, which prevents it trou- 

 bling the miners, by contaminating the ingoing air. 



There is another plan in the system of ventilation, 

 air courses. wn ich is, the crossing of air course*, that is, when in 

 the progress of ventilating a colliery, one air-course is 

 orward at right angle* to another, and has to 

 pass it, in order to produce ventilation in works upon 

 the other aide. Thi is effected in the manner re- 

 presented in Fig. 15. where a is a main road with 

 an air-course, over which the other air course b is to 

 pas*. The sides of the air-con r.- i- built with bricks, 

 arched over and made a.r-ti^ht, and a mine is driven 

 in the roof strata, as represented in the Figure. In fame 

 esses, the roof of the air-course a is laid over with plank 

 made airtight ; by 'iod, air-courses can be 



made to crosn and recross each other with great facili- 

 It has been found, from the practice of the most 

 rs, that these air-courses thus contract - 

 general six feet or at least five feet on 

 the side, that is, the area to be 36, or at least 25 square 

 feet, and that the general velocity of the current of air 

 through the works should be from three to four feet 



or about S^ miles per hour 



Another mtthod has also been brought forward for 

 >/ the air in the upcast shaft, by means of steam 

 produced from a large boiler, such aa is used lor 



Fig. 15. 



Air nrified 

 bjiuam. 



steam engines. The steam from the boiler is conduct- Mines of 

 ed in deal tubes, in preference to iron pipes, on account c ""'- 

 of deal being a very slow conductor of heat; these pipes 

 are carried at least halfway down the pit, and the in- , 

 tention is, that the steam be made to issue from the 

 lower end of the tube as hot as possible. The st. 

 immediately on coming in contact with the air, is con- 

 densed. The caloric or latent heat is disengaged, heat* 

 the air in the shaft, and produces a constant ascending 

 current, while the condensed .-team falls in a shower to 

 the pit bottom. This mode of producing an ascending 

 current of air has not the energy of the common fur- 

 nace ; and although it allows the upcast shaft to be 

 used as a pit for drawing coals, the dropping of the 

 condensed steam keeps the shaft walls wet, which is 

 not only uncomfortable, but in some degree counter- 

 acts the power of the rarity ing process. 



It has frequently been suggested by men of sci- Air propel, 

 ence, and by mining engineers, that ventilation might led imtlic- 

 be produced, both strong and effective, by propelling iual. 

 a current of air down a shaft by means of large iron 

 cylinder bellows wrought by powerful machinery. 

 From every experiment yet made, this appears to be die 

 least effective of all the plans of ventilation. 



It is well known, tliat when the least advance is Exhaustion 

 made toward- forming a vacuum, the remaining part of mir tttcc- 

 of the air instantly acting by its great elasticity, produ- tuaL 

 CM an equilibrium through the mass of air. It is this 

 principle, brought into constant action by means of 

 heat applied to the ascending current of air, that the 

 before- mentioned systems of ventilation act. 



An exhausting machine, which may be termed a Taylor'* 

 Hydraulic Air Pump, has been applied to the ventila- hjdnulic 

 tion of mines, of a moderate extent, and where there ir P" 01 ! 1 - 

 was no dangerous quantity of inflammable air. It it 

 the invention of Mr. John Taylor of Tavistock, in the 

 county of Devon, and has been applied with complete 

 success. The construction is very simple, has very lit- 

 tle friction, and shews the ingenuity of the inventor. 

 It is represented, in Fig. 1. I'late COCZCIY. where PI.ATK 

 a is a urge cistern, nearly filled with water, made of cccxciv. 

 wooden staves, hooped with iron, circular, and from r 'g- ! 

 six to eight feet in depth. Through the bottom of this 

 vessel a pipe b passes from the mine to be ventilated, 

 and passing up through die water, is carried about a 

 foot above it. I'poii the top of this pipe is an air- 

 valve, opening upwards. Over this pipe, and within 

 the sides of the cistern, a cylinder of plate iron i- pla- 

 ced, open at the bottom, but close at the top, in which 

 top an air-tight valve is placed, also opening upward-. 

 This iron cylinder is made to move in a vertical direc- 

 tion, by guides or sliders, and its upper end is attached 

 to a lever, which is moved, either by a water-whc. 

 a steam engine. When the cylinder descend-, the 

 valve e at the top of the pipe shuts, and die air contain- 

 ed in the cylinder opens die valve d in the cvlinder 

 top, and escapes, but die instant die cylinder ascends 

 the valve d shuts, and the valve c opens, by which 

 means a Quantity of air, equal to the content'- of the 

 cylinder above the -urface of the water, i- dra n from 

 die mine through die pi|>e 6 This r \haii-tion 



causes a regular circulation of air tin.. - !i the mine, to 

 supply the circulating current produced l>\ the work- 

 ing of the machine. An exh;ni-tin^ u 

 construction may be mad. mallest size to be 



.; by the hand, to any requisite size to be mo- 

 ved by machinery. 



These are die general piano which have been put in 

 practice for the ventilation of collieries with success. 



