An evening pause: Long time cavers are very familiar with the carbide lamp, as it was used routinely until around 1998, when LED lights arrived and finally superseded it.
Until then, the advantage of a carbide light was the quality of the light it produced, a soft bright glow rather than the harsh reflective rings produced by older electric lights.
The disadvantage however was the endless fiddling required to keep them working. For example, near the end of this video when he finally gets the light to work, he turns up the water flow to brighten the light. I guarantee that very soon the light would go out, as he was flooding the carbide. The water drip had to be precisely right. Too slow and not enough gas. Too fast and too much water.
I personally hated carbide lights because of that fiddling, especially because lamps made after 1970 were junk and didn’t work well. Most cavers who used carbide would scour yard sales to find old lights like this one, as older carbide lamps were made well and would work reliably.
Hat tip Jeff Poplin.