10 On preventing Accidents 



superior strata takes place, and the waste fills up, it is 

 well, as then no damp vviil accumulate, and thereby en- 

 danger the lives of the neighbouring workmen. 



Too much caution cannot be observed, by men who are 

 working near such old hollows, never to introduce their 

 candles into any cavities which may happen to be pene- 

 trated, hut immediately extinguish tiicm and retire, until 

 proper means can be adopted to ensure safety. What ac- 

 cidents have occurred for want of this simple precaution*! 



It may be, and in fact is, at times necessary, owing to 

 increase of temperature or levity in the atmosphere, to ob- 

 tain a greater supi)ly of air than is wanted in the ordinary 

 course of things, or, more properly speaking, to preserve an 

 imilbrni circulation. 



Here we have an admirable contrivance, whose powers 

 are unlimited ; and this consists in rarefying the column of 

 air in the ascending shaft by means of a fire. There ap- 

 pears to be a difference of opinion as to the best mode of 

 acconiplij^hing this. Some build a chimney or cupola upon 

 or near to the shaft, making the top thereof so close that 

 the air must pass up the chimney, at the bottom of which 

 a fire is placed : others hang, by means of a chain, &c., 

 a circular grate filled with burning fuel, down the shaft; 

 and some fix a grate in the bottom of the shaft, in a 

 heading, driven a few yards for the purpose; while others 

 cut a groove in the shaft side, which, when built up it\ 

 front, forms a chimney. 



If we are to judge of the comparative merit of the fore- 

 going plans from their respective powers of rarefaction, 

 we must give to the last method but one a decided prefe- 

 rence. By it we are enabled to produce the greatest diffe- 

 rence in weight between the two columns of air, on which 

 ventilation solely depends ; and if the grate be placed a 

 tolerable height, and opposite to the current of air passing 

 into the shaft, we shall obtain the quickest draught for the 

 fire. The chimney not only greatly increases the effects of 

 the fire, but is a sort of guard to the ropes, which might 

 be damaged by coming too near the naked fire. 



1 shall conclude this imperfect sketch, with offering a 

 few general remarks, which, to those who put them in 

 practice, will not be found useless. 



In all cases where danger from fire-damp is to be ap- 

 prehended, the miners should never work naked. It is not 



* This is a very common trick of miners, owing to an idle curiosity; and 

 but too many have paid dearly for their temerity aud want of considera- 

 tion. 



SO 



