A fire piston. A tiny piece of flash cotton, within a clear cylinder, is ignited by the heat of sudden adiabatic compression.
By Chocolateoak (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons

A fire piston. A tiny piece of flash cotton, within a clear cylinder, is ignited by the heat of sudden adiabatic compression.

By Chocolateoak (Own work) [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons