94 ANNUAL OF SCIENTIFIC DISCOVERY. 



field) about 200 a year in keeping it up, and in the payment of over- 

 lookers, there being always a danger of the fire getting, by some acci- 

 dent, such as a fall of the roof, beyond the wall into the lower wastes, 

 and burning the extensive coal-field below. Various reports have from 

 time to time been made by men of great authority in the coal-trade, 

 all of which have agreed in the utter impossibility of extinguishing 

 this fire. It will, nevertheless, readily occur that if the fire was thus, 

 as it were, corked and bottled up to itself, it ought to have gone out 

 from want of air. This, however, was not the case, for no part of the 

 fire-mine being deeper than 20 fathoms, and some of it running at no 

 great distance below the surface, it obtained a sufficient supply of air 

 thence, as well as through the leakages in the puddle-wall, to maintain a 

 smouldering, sulky and volcano-like existence sometimes more active, 

 and sometimes less so, which could be traced by occasional falls of the 

 surface, the last of which occurred about five months ago, laying bare 

 the burning waste, and discharging smoke and steam. At the request 

 of Lord Mansfield, an inspection of the fire was made by Mr. Gurney, 

 and, notwithstanding the immense extent of the burning waste, he 

 thought it possible to extinguish the fire ; and, extraordinary as it may 

 appear, this object has been effectually accomplished by a simple and 

 inexpensive process. 



We are accustomed to judge of great things by small, and, as a pop- 

 ular illustration, all the world knows practically that putting on an 

 extinguisher puts out the candle ; but perhaps few have taken the 

 trouble to consider why it does so. It is simply that the extinguisher 

 contains a very small quantity of air, of which about one fifth is oxy- 

 gen, and the rest nitrogen. As soon as this oxygen is consumed, 

 which, in so small a quantity of air as the extinguisher will hold, is 

 almost at once, nothing remains to support combustion, and the candle 

 goes out ; for the extinguisher then contains only the nitrogen of the 

 air and carbonic acid, the product of the combustion of the candle, 

 which mixture of nitrogen and carbonic acid is chokedamp. It is, of 

 course, obvious that if the fire-mine could have been similarly treated 

 it would have extinguished itself by the product of its own combustion, 

 as in the above case of the candle, and as is often the case in coal-pits. 

 The difficulty was that another element would come into the problem, 

 which was, that supposing the mine to be placed, under an extin- 

 guisher, (almost an impossibility, considering its size,) and all com- 

 bustion to have ceased, still the magazine of heat collected during so 

 many years' burning would continue, and cause the mine to reignite 

 on the readmission of fresh air. Mr. Gurney 's method of effecting this 

 object was to force a stream of chokedamp through the mine, by means 

 of the high-pressure steam-jet, at such a temperature as would, after 

 putting out the fire, cool down the mine below any degree of heat that 

 would permit it to reignite on the admission of atmospheric air, and at 

 such a pressure as to make all the leakages of the waste outwards of 

 chokedamp, so that every inlet might become an outcast by means of 

 which the atmosphere was perfectly excluded from all contact with the 

 fire. The machinery for conducting the experiment consisted of a 

 high-pressure steam-boiler, about GO feet of inch gas-pipe, and a small 



