54 



ON THE FIRE-DAMP OF COAL-MINES, 



opening in the form of a short tube. The heat of the air is- 

 suing from an aperture of this size, with a flame such as has 

 been described, I found to be 370°, the bulb of the thermome- 

 ter being in the current exactly at the orifice ; when introdu- 

 ced entirely within the aperture, and immediately above the 

 flame, it rose to 465°. Air of this temperature, it is obvious, 

 cannot inflame fire-damp, or any mixture of it. 



No very accurate adjustment is required with regard to the 

 size of the tube conveying the air into the lantern. It is suf- 

 ficient to have it wide enough ; the state of the flame is then 

 regulated entirely by the size of the upper aperture, and any 

 slight excess of width in the tube beneath is of no importance. 

 I find that with a lantern and lamp of the above size, a tube 

 three-fourths of an inch in diameter interior measure, and three 

 feet and a half in length, answers very well. This circum- 

 stance, of no accurate adjustment being necessary, gives an ad- 

 vantage to this method in actual use. Where the safety of the 

 lamp depends on such an adjustment, it is difficult to construct 

 it in such a manner that it shall burn with a bright flame, and 

 steadily, so as not to be liable to be extinguished by move- 

 ment, or by the least failure either in the current of air, or in 

 its purity. The bringing the air from the floor renders any 

 such adjustment unnecessary, and allows, therefore, of a more 

 bright and steady flame being produced with entire safety. 

 And by the lamp being thus always supplied with the purest 

 part of the air, it will continue to burn where any safety-lamp 

 on a different principle must be extinguished, and of course 

 will enable the miner to work in situations where no other will 

 be of any use. 



In fixed lamps, the length of the tube must be regulated by 

 the height of the passages The thickness of the two beds of 

 coal at Newcastle is about six feet each. But it is unequal, 



and 



