CHEMICAL SCIENCE. 195 



build a small brick furnace, four feet square, at a safe distance from the 

 down-cast shaft. The ash-pit was made entirely tight, except that it 

 had an iron cylinder thirteen inches in. diameter connected with it, 

 which terminated at an elbow under water in a tank partly filled. 

 With the upper part of this tank above the surface of the water an- 

 other pipe was connected and carried into the shaft leading down into 

 the mine. A powerful steam jet was made to work between the fur- 

 nace and the tank, which drew the air down through the fire and 

 forced it through the water, while a second jet was placed in the cyl- 

 inder at the top of the down-cast shaft, and made to draw the choke- 

 damp from the tank and force it into the pit. It should be mentioned, 

 that this choke-damp was the product of the combustion of coal as- 

 sisted by a little charcoal and lime, through which the air was passed 

 by the contrivance described, and thus was deprived of its oxygen, 

 and the azote set free. At the up-cast shaft or outlet upwards, cor- 

 responding to the down-cast shaft already mentioned, a third jet was 

 placed in a cylinder and made to exhaust from the shaft beneath, so as 

 to assist the other or compressing jets and draw the choke-damp 

 through the galleries between them. All having been arranged, the 

 apparatus was put in operation, and in order to test the choke-damp 

 and see if it was perfectly formed, burning tow moistened with turpen- 

 tine was placed in it, and was found to be immediately extinguished. 

 This experiment, therefore, was so far perfectly satisfactory. The 

 jets were kept in action, and at the expiration of two hours fire-damp 

 disappeared from the shafts, and at the up-cast shaft a slight cloudy 

 appearance was observed in the air which escaped, and this had the 

 sulphureous smell of choke. This indicated that the choke-damp had 

 passed entirely through the mine, -but in order to prove it satisfactorily 

 the draughts were shut off for a short time, and, a safety-lamp being 

 placed in the up-cast cylinder, it was immediately extinguished, prov- 

 ing the presence of the choke-damp in considerable quantities. Dur- 

 ing the two hours, six thousand cubic feet of the damp had been forced 

 into the mine every minute. After being allowed to remain closed 

 for some hours longer, the connection with the furnace was broken, 

 and fresh air was driven through the same jets, which forced out all 

 the choke-damp in about two hours. The mine was then regarded as 

 perfectly safe, and several men descended the down-cast shaft three 

 hundred and ninety feet, to the tunnel leading to the working, and all 

 was found clear. The exhausting jet having been kept up all night, 

 the next day some of the men passed through the workings and found 

 all safe. The fire was entirely extinguished, and the action of the 

 single jet was found to produce a more powerful current than could be 

 done in any other way. The experiment was therefore perfectly sat- 

 isfactory, but the steam-jet is still kept in operation to ventilate the 

 mine, which it does so effectually, that there is no need of safety- 

 lamps, and the men are working by naked candles. It will be seen 

 that by this means a great saving of time is effected in the extinguish- 

 ment of those fires to which all collieries are so liable, as, instead of 

 the months or years required for sealing up, flooding, and pumping 

 out again, only two days are necessary to extinguish the most violent 

 fire, and this, too, at a very trifling expense. 



