AND ON PREVENTING ITS EXPLOSION. 47 



holding in the hand a candle within a glass case, having a tube 

 attached to it supplying air from near the floor. The supply 

 of air to support the combustion being thus from beneath, the 

 presence of carbonic acid gas to any hazardous extent would 

 soon be discovered, by the flame of the lamp becoming fainter, 

 and being at length extinguished, while the respiration of the 

 individual would not be affected: And by raising the open 

 end of the tube to different heights from the ground, the ex- 

 tent to which the atmosphere of carbonic acid reached would 

 be ascertained. By establishing in mines in which the choak- 

 damp is liable to occur, a system of lighting similar to that 

 which has been described, the danger from it would be effec- 

 tually obviated. 



NOTES. 



