Safety valve, Ramsbottom type.

Safety valves act as a fail-safe, releasing pressure and ensuring that locomotive boilers do not explode in the case of failure. Safety valves had been used since the early days of the railways, but in 1856 John Ramsbottom invented a type valve that was tamper proof - crews sometimes adjusted the valves to increase a locomotive's power.

Ramsbottom's safety valve consisted of two valves pressed down with a spring-loaded lever.