f On preventing Accidents 



by having these headings properly constructed, it may not 

 be amiss to state generally what should be observed in 

 forming them. 



The /Irsi thing to be attended to is, to have the air- and 

 waggon- ways of a sufficient width and height, so as to ad- 

 mit an abundant quantity of air to carry off the extricated 

 gases ; and in proportioning them, it would be well to attend 

 to the extent and number of air-ways, Ecc, or the area 

 of mine required to be got or worked lo a shaft ; and like- 

 wise to the quantity of gas likely to be evolved. In thin 

 mines of coal, this ought to be an important consideration. 

 No passages or headings, in situations where the workings 

 are likely to be extensive, ought to be less than four feet 

 and a half square. There is a lateral friction occasioned 

 by air passing through apertures of every description, and 

 this is in proportion to the area of their sides, if smooth; 

 and is increased by the roughness and irregularity of the 

 surface passed over, as well as by contractions*'. There 

 are other obstructions to a regular circulation, such as the 

 opening of doors, men or horses, &c. Sec, passing in a 

 direction contrary to the current of air; and these circum- 

 jltaiices render capacious air-ways indispensable. 



Secondly. Every part of such air- and waggon- ways should 

 be made as secure as possible; for, when they are left in an 

 unfinished and temporary state, they must needs, ere long, 

 be repaired, at an additional expense, to say nothing of the 

 hindrances and accidents to which such slovenly manage- 

 ment is liable. 



Thirdly. Thrills should be made nearly as large as the. 

 air-ways ; a number of contractions of this kind would ren- 

 der a capacious air-way of no service. When they are 

 made up, great attention should be paid to their being air- 

 tight, otherwise the air will be lost, and the current thereby 

 considerably diminished. 



Fourthly, Doors for the purpose of turning the air 

 should be well made, very tight, and firmly fixed. They 

 are sometimes constructed with springs, &:c., so as to shut 

 of themselves ; but as the most simple contrivances are 

 found to answer best^ these do not generally obtain. There 

 is a method of construction, which appears to me to be 

 capable of answering very well, namely, swing doors, which 

 if properly framed together, and suspended by double cen- 

 tres, will shut of themselves, and open wiih little trouble; 



* Any person may satisfy himself of the truth of this, by noting the re- 

 jTuIar current of air tlirougK the windings of a coal raiiie, and then causing^ 

 the air to pasa directly between the two shafts. 



they 



