114 Mr Bald on the Fires that take place in Collieries. 



The rectangular lines represent the mine which is to be carried 

 around the burning mass, along the pavement of the coal. In 

 this mine, a puddle of clay, of from six to eight feet thick, is to 

 be carried all round from the roof to the pavement of the coal ; 

 then, there is to be left an open air-course, of about five feet 

 wide around ; and upon the other side of this mine or air- 

 course, a clay-puddle, similar to the former, and parallel with 

 it, is also to be carried round \ and the object is this : — when the 

 burning extends to the inner clay-puddle, it may become heat- 

 ed ; but the caloric, as fast as it is generated, will ascend to the 

 surface by the mines a and b; and the other clay-puddle will, it 

 is expected, effectually prevent the heat from extending to the 

 coal-pillars on the other side. Besides, the air-course gives a 

 ready access to the miners around the burning mass, to repair 

 any breaches in the puddle ; and if need be, water can be intro- 

 duced, in the extremity of the case, betwixt the two puddle- walls. 

 The small dots represent the fire or burning mass, which exists 

 chiefly in the rubbish of the mine. 



This is a very hazardous operation for the workmen, on ac- 

 count of the deleterious vapours ; and, for their security, a pit has 

 been sunk to the coal at c, in order that, as soon as the mine 

 communicates with the pit, the fresh atmospheric air may de- 

 scend the pit, and ascend by the mines to the surface ; and we 

 know that this determination of the air will take place, both from 

 physical principles, and from experience. The workmen will 

 then always descend by the pit, where the fresh air is going 

 down, and thus secure to themselves, at all times, a safe retreat. 

 Without this precaution the miners could not pursue their work 

 in the mine. Hitherto the mine has gone on successfully, al- 

 though with danger ; and we have every hope that the enemy 

 will be eventually subdued. 



The Polton Colliery was discovered to bfe also on fire, in No- 

 vember last, in the wastes of the eight feet coal. 



The air in this coal having stagnated, and become unfit for the 

 respiration of the miners, a large circular iron grate was, (pre- 

 vious to the fire taking place,) suspended from the top of the 

 pit containing burning coals, in order to rarify the air in the 

 shaft, and produce a circulation, which had the desired effect. 

 See Fig. 4. Plate III ; but one day, some mischievous boys dis- 



