To a caver, light is everything. I learned this simple truth a long time ago when I first started caving. You see, the sun never rises in a cave.
Darkness is forever.
Thus began my quest for a reliable cave light. Like so many people of that era, I used a carbide lamp as my primary light source, a flashlight as my secondary light source and candles as my tertiary light source. The theory was that you carried enough carbide and spare parts so you could fix any problem with the carbide lamp. The flashlight would allow you to get things fixed or find your way out in a pinch. The candles would give you light and heat for an extended emergency stay.